All Problems
Output a string to the console
Write the string
"Hello World!" to STDOUT
fsharp
printfn "Hello World!"
cpp
std::cout << "Hello World" << std::endl;
std::printf("Hello World\n");
Console::WriteLine(L"Hello World");
Retrieve a string containing ampersands from the variables in a url
My PHP script first does a query to obtain customer info for a form. The form has first name and last name fields among others. The customer has put entries such as
The script variable for first name $_REQUEST
I have tried various functions like urldecode but all to no avail. I even tried encoding the url before the view screen is painted so that the url looks like
Of course this fails for the same reasons. What is a better approach?
"Ron & Jean" in the first name field in the database. Then the edit form script is called with variables such as
"http://myserver.com/custinfo/edit.php?mode=view&fname=Ron & Jean&lname=Smith".
The script variable for first name $_REQUEST
['firstname'] never gets beyond the "Ron" value because of the ampersand in the data.
I have tried various functions like urldecode but all to no avail. I even tried encoding the url before the view screen is painted so that the url looks like
"http://myserver/custinfo/edit.php?mode=view&fname="Ronxxnbsp;xxamp;xxnbsp;Jean"&lname=SMITH". (sorry I had to add the xx to replace the ampersand or it didn't display meaningful url contents the browser sees.)
Of course this fails for the same reasons. What is a better approach?
fsharp
//the problem arises due to the fact that you've attempted to apply HTML entities encoding rather than URL encoding to your data!
//in F#, for example, assuming you would call this function with fname and lname parameters, this would produce the desired output
let getProperUrl fname lname = sprintf "http://myserver.com/custinfo/edit.php?mode=view&fname=%s&lname=%s" (HttpUtility.UrlEncode fname) (HttpUtility.UrlEncode lname)
//in F#, for example, assuming you would call this function with fname and lname parameters, this would produce the desired output
let getProperUrl fname lname = sprintf "http://myserver.com/custinfo/edit.php?mode=view&fname=%s&lname=%s" (HttpUtility.UrlEncode fname) (HttpUtility.UrlEncode lname)
// Example that shows encoding and decoding:
let queryString =
let fname = HttpUtility.UrlEncode("Ron & James")
let lname = HttpUtility.UrlEncode("Smith & Jones")
sprintf "http://myserver.com/custinfo/edit.php?mode=view&fname=%s&lname=%s" fname lname
/// All parameters in the URL as a lookup map
let parameters =
let paramStart = queryString.IndexOf('?')
if paramStart < 0 then
Map.empty
else
let values =
queryString.Substring(paramStart + 1)
|> HttpUtility.ParseQueryString
values.AllKeys
|> Seq.map (fun key -> key, values.[key])
|> Map.ofSeq
let fname = parameters.TryFind("fname")
let lname = parameters.TryFind("lname")
let queryString =
let fname = HttpUtility.UrlEncode("Ron & James")
let lname = HttpUtility.UrlEncode("Smith & Jones")
sprintf "http://myserver.com/custinfo/edit.php?mode=view&fname=%s&lname=%s" fname lname
/// All parameters in the URL as a lookup map
let parameters =
let paramStart = queryString.IndexOf('?')
if paramStart < 0 then
Map.empty
else
let values =
queryString.Substring(paramStart + 1)
|> HttpUtility.ParseQueryString
values.AllKeys
|> Seq.map (fun key -> key, values.[key])
|> Map.ofSeq
let fname = parameters.TryFind("fname")
let lname = parameters.TryFind("lname")
cpp
QUrl url("http://myserver.com/custinfo/edit.php");
url.addQueryItem("mode", "view");
url.addQueryItem("fname", "Ron & Jean");
url.addQueryItem("lname", "Smith");
QByteArray encodedUrl = url.toEncoded();
url.addQueryItem("mode", "view");
url.addQueryItem("fname", "Ron & Jean");
url.addQueryItem("lname", "Smith");
QByteArray encodedUrl = url.toEncoded();
string-wrap
Wrap the string
Expected output:
> The quick brown fox jumps over the lazy dog. The quick brown fox jumps over t
> he lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox
> jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The qui
> ck brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy
> dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps o
> ver the lazy dog. The quick brown fox jumps over the lazy dog.
"The quick brown fox jumps over the lazy dog. " repeated ten times to a max width of 78 chars, starting each line with "> "
Expected output:
> The quick brown fox jumps over the lazy dog. The quick brown fox jumps over t
> he lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox
> jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The qui
> ck brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy
> dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps o
> ver the lazy dog. The quick brown fox jumps over the lazy dog.
cpp
#include <iostream>
#include <sstream>
#include <string>
using namespace std;
void rep(ostream &os, const string& str, int times)
{
while (times--)
os << str;
}
void wrap(ostream &os, const string& str, const string &prefix, int width)
{
for (int offset = 0; offset < str.size(); offset += width)
os << prefix << str.substr(offset, width) << endl;
}
int main()
{
stringstream input;
rep(input, "The quick brown fox jumps over the lazy dog. ", 10);
wrap(cout, input.str(), "> ", 78);
}
#include <sstream>
#include <string>
using namespace std;
void rep(ostream &os, const string& str, int times)
{
while (times--)
os << str;
}
void wrap(ostream &os, const string& str, const string &prefix, int width)
{
for (int offset = 0; offset < str.size(); offset += width)
os << prefix << str.substr(offset, width) << endl;
}
int main()
{
stringstream input;
rep(input, "The quick brown fox jumps over the lazy dog. ", 10);
wrap(cout, input.str(), "> ", 78);
}
Define a string containing special characters
Define the literal string
"\#{'}${"}/"
fsharp
let special = "\#{'}${\"}/"
cpp
std::string special = "\\#{'}${\"}/";
String^ special = L"\\#{'}${\"}/";
Define a multiline string
Define the string:
"This
Is
A
Multiline
String"
fsharp
let multiline = "This\nIs\nA\nMultiline\nString"
let multiline = "This
Is
A
Multiline
String"
Is
A
Multiline
String"
cpp
std::string text =
"This\n"
"Is\n"
"A\n"
"Multiline\n"
"String";
"This\n"
"Is\n"
"A\n"
"Multiline\n"
"String";
String^ text = L"This\nIs\nA\nMultiline\nString";
std::string text = "This\nIs\nA\nMultiline\nString";
Define a string containing variables and expressions
Given variables a=3 and b=4 output
"3+4=7"
fsharp
let a, b = 3, 4
let mystr = sprintf "%d+%d=%d" a b (a+b)
printfn "%s" mystr
let mystr = sprintf "%d+%d=%d" a b (a+b)
printfn "%s" mystr
cpp
Console::WriteLine(L"{0}+{1}={2}", a, b, a+b);
std::printf("%d+%d=%d\n", a, b, a+b);
std::cout << boost::format("%|1|+%|1|=%|1|") % a % b % (a+b) << std::endl;
Reverse the characters in a string
Given the string
"reverse me", produce the string "em esrever"
fsharp
let reversed = new String (Array.rev ("reverse me".ToCharArray()))
let word = "reverse me"
//reverse the word
let reversedword =
word.ToCharArray()
|> Array.fold(fun acc x -> x::acc) []
//reverse the word
let reversedword =
word.ToCharArray()
|> Array.fold(fun acc x -> x::acc) []
cpp
String^ s = "reverse me";
array<Char>^ sa = s->ToCharArray();
Array::Reverse(sa);
String^ sr = gcnew String(sa);
array<Char>^ sa = s->ToCharArray();
Array::Reverse(sa);
String^ sr = gcnew String(sa);
std::string s = "reverse me";
std::reverse(s.begin(), s.end());
std::reverse(s.begin(), s.end());
std::string s = "reverse me";
std::string sr(s.rbegin(), s.rend());
std::string sr(s.rbegin(), s.rend());
std::string s = "reverse me";
std::swap_ranges(s.begin(), (s.begin() + s.size() / 2), s.rbegin());
std::swap_ranges(s.begin(), (s.begin() + s.size() / 2), s.rbegin());
Reverse the words in a string
Given the string
"This is a end, my only friend!", produce the string "friend! only my end, the is This"
fsharp
let reversed = String.Join(" ", Array.rev("This is the end, my only friend!".Split [|' '|]))
cpp
array<Char>^ sep = {L' '};
array<String^>^ words =
String(L"This is the end, my only friend!").Split(sep, StringSplitOptions::RemoveEmptyEntries);
Array::Reverse(words); String^ newwords = String::Join(L" ", words);
array<String^>^ words =
String(L"This is the end, my only friend!").Split(sep, StringSplitOptions::RemoveEmptyEntries);
Array::Reverse(words); String^ newwords = String::Join(L" ", words);
std::string words = "This is the end, my only friend!"; std::vector<std::string> swv;
boost::split(swv, words, boost::is_any_of(" ")); std::reverse(swv.begin(), swv.end());
std::string newwords = (std::for_each(swv.begin(), swv.end(), StringTAndJ())).value();
boost::split(swv, words, boost::is_any_of(" ")); std::reverse(swv.begin(), swv.end());
std::string newwords = (std::for_each(swv.begin(), swv.end(), StringTAndJ())).value();
Text wrapping
Wrap the string
> The quick brown fox jumps over the lazy dog. The quick brown fox jumps
> over the lazy dog. The quick brown fox jumps over the lazy dog. The
> quick brown fox jumps over the lazy dog. The quick brown fox jumps
> over the lazy dog. The quick brown fox jumps over the lazy dog. The
> quick brown fox jumps over the lazy dog. The quick brown fox jumps
> over the lazy dog. The quick brown fox jumps over the lazy dog. The
> quick brown fox jumps over the lazy dog.
"The quick brown fox jumps over the lazy dog. " repeated ten times to a max width of 78 chars, starting each line with "> ", yielding this result:
> The quick brown fox jumps over the lazy dog. The quick brown fox jumps
> over the lazy dog. The quick brown fox jumps over the lazy dog. The
> quick brown fox jumps over the lazy dog. The quick brown fox jumps
> over the lazy dog. The quick brown fox jumps over the lazy dog. The
> quick brown fox jumps over the lazy dog. The quick brown fox jumps
> over the lazy dog. The quick brown fox jumps over the lazy dog. The
> quick brown fox jumps over the lazy dog.
fsharp
let prefix = "> "
let input = "The quick brown fox jumps over the lazy dog. "
(String.split ['\n'] (textwrap (copies input 10) (73 - prefix.Length))) |> List.iter (fun line -> printfn "%s%s" prefix line)
let input = "The quick brown fox jumps over the lazy dog. "
(String.split ['\n'] (textwrap (copies input 10) (73 - prefix.Length))) |> List.iter (fun line -> printfn "%s%s" prefix line)
let output maxWidth (s: string) =
let rec wrap = function
| lineSoFar, ([| |]: string array)-> printfn "%s" lineSoFar
| ">" as lineSoFar, (words: string array) ->
// Handle this case separately, thus we can also deal with
// cases where a word is longer then the max width
wrap (lineSoFar + " " + words.[0], Array.sub words 1 (words.Length - 1))
| lineSoFar, words when words.[0].Length + lineSoFar.Length >= maxWidth ->
printfn "%s" lineSoFar
wrap (">", words)
| lineSoFar, words ->
wrap(lineSoFar + " " + words.[0], Array.sub words 1 (words.Length - 1))
wrap (">", s.Split([| ' ' |]))
[| for i in 1 .. 10 do yield "The quick brown fox jumps over the lazy dog." |]
|> String.concat " "
|> output 78
let rec wrap = function
| lineSoFar, ([| |]: string array)-> printfn "%s" lineSoFar
| ">" as lineSoFar, (words: string array) ->
// Handle this case separately, thus we can also deal with
// cases where a word is longer then the max width
wrap (lineSoFar + " " + words.[0], Array.sub words 1 (words.Length - 1))
| lineSoFar, words when words.[0].Length + lineSoFar.Length >= maxWidth ->
printfn "%s" lineSoFar
wrap (">", words)
| lineSoFar, words ->
wrap(lineSoFar + " " + words.[0], Array.sub words 1 (words.Length - 1))
wrap (">", s.Split([| ' ' |]))
[| for i in 1 .. 10 do yield "The quick brown fox jumps over the lazy dog." |]
|> String.concat " "
|> output 78
cpp
String^ input = ::copies("The quick brown fox jumps over the lazy dog. ", 10);
String^ sep = " "; String^ prefix = "> ";
String^ wrapped = textwrap(input, 74 - prefix->Length, sep, prefix);
Console::WriteLine("{0}", wrapped);
String^ sep = " "; String^ prefix = "> ";
String^ wrapped = textwrap(input, 74 - prefix->Length, sep, prefix);
Console::WriteLine("{0}", wrapped);
void rep(ostream &os, const string& str, int times)
{
while (times--)
os << str;
}
void wrap(ostream &os, const string& str, const string &prefix, int width)
{
int line_len = width;
bool first_word = true;
width -= prefix.size();
BOOST_FOREACH(string word, tokenizer<char_separator<char>>(str, char_separator<char>(" ")))
{
line_len += word.size();
if (line_len++ < width)
os << ' ';
else {
if (first_word)
first_word = false;
else
os << endl;
os << prefix;
line_len = word.size();
}
os << word;
}
os << endl;
}
int main()
{
stringstream input;
rep(input, "The quick brown fox jumps over the lazy dog. ", 10);
wrap(cout, input.str(), "> ", 72);
}
{
while (times--)
os << str;
}
void wrap(ostream &os, const string& str, const string &prefix, int width)
{
int line_len = width;
bool first_word = true;
width -= prefix.size();
BOOST_FOREACH(string word, tokenizer<char_separator<char>>(str, char_separator<char>(" ")))
{
line_len += word.size();
if (line_len++ < width)
os << ' ';
else {
if (first_word)
first_word = false;
else
os << endl;
os << prefix;
line_len = word.size();
}
os << word;
}
os << endl;
}
int main()
{
stringstream input;
rep(input, "The quick brown fox jumps over the lazy dog. ", 10);
wrap(cout, input.str(), "> ", 72);
}
Remove leading and trailing whitespace from a string
Given the string
" hello " return the string "hello".
fsharp
let s = " hello "
let trimmed = s.Trim()
let trimmed = s.Trim()
let trimmed = " hello ".Trim()
cpp
String^ s = " hello "; String^ trimmed = s->Trim();
Simple substitution cipher
Take a string and return the ROT13 and ROT47 (Check Wikipedia) version of the string.
For example:
String is: Hello World #123
ROT13 returns: Uryyb Jbeyq #123
ROT47 returns: w6==@ (@C=5 R`ab
For example:
String is: Hello World #123
ROT13 returns: Uryyb Jbeyq #123
ROT47 returns: w6==@ (@C=5 R`ab
fsharp
#light
let rotChar (s:int) (l:int) (h:int) (c:char) =
let charCode = int c
let letterCount = h - l + 1
let newCharCode = (charCode - l + s) % letterCount + l
char newCharCode
let rot13 (text:string) =
let rotChar13 = function
| (c:char) when 'A' <= c && c <= 'Z' -> rotChar 13 (int 'A') (int 'Z') c
| c when 'a' <= c && c <= 'z' -> rotChar 13 (int 'a') (int 'z') c
| c -> c
new string([| for c in text -> rotChar13 c|])
let rot47 (text:string) =
let rotChar47 = function
| ' ' as c -> c
| c -> rotChar 47 (int '!') (int '~') c
new string([| for c in text -> rotChar47 c |])
let rotChar (s:int) (l:int) (h:int) (c:char) =
let charCode = int c
let letterCount = h - l + 1
let newCharCode = (charCode - l + s) % letterCount + l
char newCharCode
let rot13 (text:string) =
let rotChar13 = function
| (c:char) when 'A' <= c && c <= 'Z' -> rotChar 13 (int 'A') (int 'Z') c
| c when 'a' <= c && c <= 'z' -> rotChar 13 (int 'a') (int 'z') c
| c -> c
new string([| for c in text -> rotChar13 c|])
let rot47 (text:string) =
let rotChar47 = function
| ' ' as c -> c
| c -> rotChar 47 (int '!') (int '~') c
new string([| for c in text -> rotChar47 c |])
cpp
#include <algorithm>
#include <iostream>
#include <cctype>
using namespace std;
int rot13(int c) {
if (!isalpha(c)) {
return c;
} else {
char start = islower(c) ? 'a' : 'A';
return ((c - start) + 13) % 26 + start;
}
}
int rot47(int c) {
if (c < 33 || c > 126) {
return c;
} else {
return ((c - 33) + 47) % 94 + 33;
}
}
int main(int argc, char **argv) {
for (int i = 0; i < argc; ++i) {
string original = argv[i];
string rot13enc = original;
transform(original.begin(), original.end(), rot13enc.begin(), rot13);
string rot47enc = original;
transform(original.begin(), original.end(), rot47enc.begin(), rot47);
cout << "original: " << original << endl
<< "rot 13: " << rot13enc << endl
<< "rot 47: " << rot47enc << endl;
}
return 0;
}
#include <iostream>
#include <cctype>
using namespace std;
int rot13(int c) {
if (!isalpha(c)) {
return c;
} else {
char start = islower(c) ? 'a' : 'A';
return ((c - start) + 13) % 26 + start;
}
}
int rot47(int c) {
if (c < 33 || c > 126) {
return c;
} else {
return ((c - 33) + 47) % 94 + 33;
}
}
int main(int argc, char **argv) {
for (int i = 0; i < argc; ++i) {
string original = argv[i];
string rot13enc = original;
transform(original.begin(), original.end(), rot13enc.begin(), rot13);
string rot47enc = original;
transform(original.begin(), original.end(), rot47enc.begin(), rot47);
cout << "original: " << original << endl
<< "rot 13: " << rot13enc << endl
<< "rot 47: " << rot47enc << endl;
}
return 0;
}
Make a string uppercase
Transform
"Space Monkey" into "SPACE MONKEY"
fsharp
printfn "%s" ("Space Monkey".ToUpper())
printfn "%s" (String.uppercase "Space Monkey")
cpp
String(L"Space Monkey").ToUpper();
std::string s = "Space Monkey";
std::transform(s.begin(), s.end(), s.begin(), std::toupper);
std::transform(s.begin(), s.end(), s.begin(), std::toupper);
std::string s = "Space Monkey";
boost::to_upper(s);
boost::to_upper(s);
Make a string lowercase
Transform
"Caps ARE overRated" into "caps are overrated"
fsharp
printfn "%s" ("Caps ARE overRated".ToLower())
printfn "%s" (String.lowercase "Caps ARE overRated")
cpp
std::string s = "Caps ARE overRated";
std::string sl(boost::to_lower_copy(s));
std::string sl(boost::to_lower_copy(s));
String(L"Caps ARE overRated").ToLower();
Capitalise the first letter of each word
Transform
"man OF stEEL" into "Man Of Steel"
fsharp
let words = String.Join(" ", Array.map (fun (s : String) -> (String.capitalize (s.ToLower()))) ("man OF stEEL".Split [|' '|]))
let wordlst = List.map (fun s -> (String.capitalize (String.lowercase s))) (String.split [' '] "man OF stEEL")
let words = new StringBuilder(List.hd wordlst)
for (s : String) in (List.tl wordlst) do (words.Append(" ").Append(s))
let words = new StringBuilder(List.hd wordlst)
for (s : String) in (List.tl wordlst) do (words.Append(" ").Append(s))
// Previous solutions used old library functions, here's something that works with F# 2.0
let s= "man OF stEEL"
let UpperFirst = function | "" -> "" | s -> s.Substring(0,1).ToUpper() + s.Substring(1).ToLower()
s.Split(' ') |> Array.map UpperFirst |> String.concat " "
let s= "man OF stEEL"
let UpperFirst = function | "" -> "" | s -> s.Substring(0,1).ToUpper() + s.Substring(1).ToLower()
s.Split(' ') |> Array.map UpperFirst |> String.concat " "
let culture = System.Globalization.CultureInfo.GetCultureInfo("en-US")
let titleCase = culture.TextInfo.ToTitleCase "man oF sTeel"
let titleCase = culture.TextInfo.ToTitleCase "man oF sTeel"
cpp
std::string words = "mAn OF stEEL";
std::transform(words.begin(), words.end(), words.begin(), ToCaps<>());
std::transform(words.begin(), words.end(), words.begin(), ToCaps<>());
StringBuilder^ sb = gcnew StringBuilder(L"man OF stEEL");
for (int i = 0, isFirst = 1; i < sb->Length; ++i)
{
sb[i] = Char::IsWhiteSpace(sb[i]) ? (isFirst = 1, sb[i]) : isFirst ? (isFirst = 0, Char::ToUpper(sb[i])) : Char::ToLower(sb[i]);
}
for (int i = 0, isFirst = 1; i < sb->Length; ++i)
{
sb[i] = Char::IsWhiteSpace(sb[i]) ? (isFirst = 1, sb[i]) : isFirst ? (isFirst = 0, Char::ToUpper(sb[i])) : Char::ToLower(sb[i]);
}
std::string words = "mAn OF stEEL";
std::vector<std::string> swv;
boost::split(swv, words, boost::is_any_of(" "));
std::string newwords = (std::for_each(swv.begin(), swv.end(), StringTAndJ(WordToCaps))).value();
std::vector<std::string> swv;
boost::split(swv, words, boost::is_any_of(" "));
std::string newwords = (std::for_each(swv.begin(), swv.end(), StringTAndJ(WordToCaps))).value();
Find the distance between two points
fsharp
let distance' = distance (34, 78) (67, -45)
printfn "%3.2f" distance'
printfn "%3.2f" distance'
cpp
Point p1 = {34, 78}, p2 = {67, -45};
double distance = ::distance(p1, p2);
Console::WriteLine("{0,3:F2}", distance);
double distance = ::distance(p1, p2);
Console::WriteLine("{0,3:F2}", distance);
Zero pad a number
Given the number 42, pad it to 8 characters like 00000042
fsharp
printfn "%08d" 42
let formatted = sprintf "%08d" 42
printfn "%s" formatted
printfn "%s" formatted
let buffer = new StringBuilder()
Printf.bprintf buffer "%08d" 42
printfn "%s" (buffer.ToString())
Printf.bprintf buffer "%08d" 42
printfn "%s" (buffer.ToString())
let formatted = String.Format("{0,8:D8}", 42)
Console.WriteLine(formatted)
Console.WriteLine(formatted)
let formatted = Convert.ToString(42).PadLeft(8, '0')
Console.WriteLine(formatted)
Console.WriteLine(formatted)
cpp
String^ formatted = Convert::ToString(42)->PadLeft(8, '0');
String^ formatted = String::Format("{0,8:D8}", 42);
std::printf("%08d", 42);
std::ostringstream os;
os << std::setw(8) << std::setfill('0') << 42 << std::ends;
std::cout << os.str() << std::endl;
os << std::setw(8) << std::setfill('0') << 42 << std::ends;
std::cout << os.str() << std::endl;
std::cout << boost::format("%|08|") % 42 << std::endl;
Right Space pad a number
Given the number 1024 right pad it to 6 characters
"1024 "
fsharp
printfn "%-6d" 1024
let formatted = String.Format("{0,-6:D}", 1024)
Console.WriteLine(formatted)
Console.WriteLine(formatted)
let formatted = Convert.ToString(1024).PadRight(6)
Console.WriteLine(formatted)
Console.WriteLine(formatted)
cpp
String^ formatted = Convert::ToString(1024)->PadRight(6);
String^ formatted = String::Format("{0,-6:D}", 1024);
std::printf("%-6d\n", 1024);
std::ostringstream os;
os << std::setw(6) << std::setfill(' ') << std::left << 1024 << std::ends;
std::cout << os.str() << std::endl;
os << std::setw(6) << std::setfill(' ') << std::left << 1024 << std::ends;
std::cout << os.str() << std::endl;
std::cout << boost::format("%|-6|") % 1024 << std::endl;
Format a decimal number
Format the number 7/8 as a decimal with 2 places: 0.88
fsharp
printfn "%3.2f" (0.7 / 0.8)
let formatted = String.Format("{0,3:F2}", (0.7 / 0.8))
Console.WriteLine(formatted)
Console.WriteLine(formatted)
cpp
String^ formatted = String::Format("{0,3:F2}", result);
Console::WriteLine("{0,3:F2}", (7. / 8.));
std::printf("%3.2f\n", result);
std::ostringstream os;
os.width(3); os.fill('0'); os.setf(std::ios::fixed|std::ios::showpoint); os.precision(2);
os << result << std::ends;
std::cout << os.str() << std::endl;
os.width(3); os.fill('0'); os.setf(std::ios::fixed|std::ios::showpoint); os.precision(2);
os << result << std::ends;
std::cout << os.str() << std::endl;
std::cout << boost::format("%|3.2f|") % result << std::endl;
Left Space pad a number
Given the number 73 left pad it to 10 characters
" 73"
fsharp
let formatted = sprintf "%10d" 73
printfn "%s" formatted
printfn "%s" formatted
let formatted = String.Format("{0,10:D}", 73)
Console.WriteLine(formatted)
Console.WriteLine(formatted)
let formatted = Convert.ToString(73).PadLeft(10)
Console.WriteLine(formatted)
Console.WriteLine(formatted)
cpp
String^ formatted = Convert::ToString(73)->PadLeft(10);
String^ formatted = String::Format("{0,10:D}", 73);
std::printf("%10d\n", 73);
std::ostringstream os;
os << std::setw(10) << std::setfill(' ') << 73 << std::ends;
std::cout << os.str() << std::endl;
os << std::setw(10) << std::setfill(' ') << 73 << std::ends;
std::cout << os.str() << std::endl;
std::cout << boost::format("%|10|") % 73 << std::endl;
Generate a random integer in a given range
Produce a random integer between 100 and 200 inclusive
fsharp
let rnd = new Random()
let rndInt = rnd.Next(100, 201)
let rndInt = rnd.Next(100, 201)
cpp
Random^ rnd = gcnew Random;
int rndInt = rnd->Next(100, 201);
int rndInt = rnd->Next(100, 201);
std::srand(std::time(NULL));
unsigned lb = 100, ub = 200;
unsigned rnd = lb + (rand() % ((ub - lb) + 1));
unsigned lb = 100, ub = 200;
unsigned rnd = lb + (rand() % ((ub - lb) + 1));
typedef boost::uniform_int<> Distribution;
typedef boost::mt19937 RNG;
Distribution distribution(100, 200);
RNG rng; rng.seed(std::time(NULL));
boost::variate_generator<RNG&, Distribution> generator(rng, distribution);
unsigned rnd = generator();
typedef boost::mt19937 RNG;
Distribution distribution(100, 200);
RNG rng; rng.seed(std::time(NULL));
boost::variate_generator<RNG&, Distribution> generator(rng, distribution);
unsigned rnd = generator();
Generate a repeatable random number sequence
Initialise a random number generator with a seed and generate five decimal values. Reset the seed and produce the same values.
fsharp
let (seed, lb, ub) = (12345, 100, 200)
let mutable rnd = new Random(seed)
for i = 1 to 5 do printf "%d " (rnd.Next(lb, ub + 1)) done ; printfn ""
rnd <- new Random(seed)
for i = 1 to 5 do printf "%d " (rnd.Next(lb, ub + 1)) done ; printfn ""
let mutable rnd = new Random(seed)
for i = 1 to 5 do printf "%d " (rnd.Next(lb, ub + 1)) done ; printfn ""
rnd <- new Random(seed)
for i = 1 to 5 do printf "%d " (rnd.Next(lb, ub + 1)) done ; printfn ""
cpp
void printAction(int i) { Console::Write("{0} ", i); }
array<int>^ genFillRand(array<int>^ arr, Random^ rnd, int lb, int ub)
{
for (int i = 0; i < arr->Length; ++i) arr[i] = rnd->Next(lb, ub + 1); return arr;
}
int main()
{
array<int>^ arr1 = genFillRand(gcnew array<int>(5), gcnew Random(12345), 100, 200);
array<int>^ arr2 = genFillRand(gcnew array<int>(5), gcnew Random(12345), 100, 200);
Action<int>^ print = gcnew Action<int>(printAction);
Array::ForEach<int>(arr1, print); Console::WriteLine();
Array::ForEach<int>(arr2, print); Console::WriteLine();
}
array<int>^ genFillRand(array<int>^ arr, Random^ rnd, int lb, int ub)
{
for (int i = 0; i < arr->Length; ++i) arr[i] = rnd->Next(lb, ub + 1); return arr;
}
int main()
{
array<int>^ arr1 = genFillRand(gcnew array<int>(5), gcnew Random(12345), 100, 200);
array<int>^ arr2 = genFillRand(gcnew array<int>(5), gcnew Random(12345), 100, 200);
Action<int>^ print = gcnew Action<int>(printAction);
Array::ForEach<int>(arr1, print); Console::WriteLine();
Array::ForEach<int>(arr2, print); Console::WriteLine();
}
typedef boost::uniform_int<> Distribution;
typedef boost::mt19937 RNG;
Distribution distribution(100, 200);
RNG rng;
boost::variate_generator<RNG&, Distribution> generator(rng, distribution);
rng.seed(42L);
std::generate_n(std::ostream_iterator<unsigned>(std::cout, " "), 5, generator);
rng.seed(42L);
std::cout << std::endl;
std::generate_n(std::ostream_iterator<unsigned>(std::cout, " "), 5, generator);
typedef boost::mt19937 RNG;
Distribution distribution(100, 200);
RNG rng;
boost::variate_generator<RNG&, Distribution> generator(rng, distribution);
rng.seed(42L);
std::generate_n(std::ostream_iterator<unsigned>(std::cout, " "), 5, generator);
rng.seed(42L);
std::cout << std::endl;
std::generate_n(std::ostream_iterator<unsigned>(std::cout, " "), 5, generator);
Check if a string matches a regular expression
Display
"ok" if "Hello" matches /[A-Z][a-z]+/
fsharp
if (Regex.IsMatch("Hello", "[A-Z][a-z]+")) then printfn "ok"
cpp
if ((gcnew Regex("[A-Z][a-z]+"))->IsMatch("Hello")) Console::WriteLine("ok");
if (Regex::IsMatch("Hello", "[A-Z][a-z]+")) Console::WriteLine("ok");
Regex^ rx = gcnew Regex("[A-Z][a-z]+");
if (rx->IsMatch("Hello")) Console::WriteLine("ok");
if (rx->IsMatch("Hello")) Console::WriteLine("ok");
cmatch what;
if (regex_match("Hello", what, regex("[A-Z][a-z]+")))
cout << "ok" << endl;
if (regex_match("Hello", what, regex("[A-Z][a-z]+")))
cout << "ok" << endl;
Check if a string matches with groups
Display
"two" if "one two three" matches /one (.*) three/
fsharp
let regmatch = (Regex.Match("one two three", "one (.*) three"))
if regmatch.Success then (printfn "%s" (regmatch.Groups.[1].Captures.[0].ToString()))
if regmatch.Success then (printfn "%s" (regmatch.Groups.[1].Captures.[0].ToString()))
cpp
Match^ match = Regex::Match("one two three", "one (.*) three");
if (match->Success) Console::WriteLine("{0}", match->Groups[1]->Captures[0]);
if (match->Success) Console::WriteLine("{0}", match->Groups[1]->Captures[0]);
cmatch what;
if (regex_match("one two three", what, regex("one (.*) three")))
cout << what[1] << endl;
if (regex_match("one two three", what, regex("one (.*) three")))
cout << what[1] << endl;
Check if a string contains a match to a regular expression
Display
"ok" if "abc 123 @#$" matches /\d+/
fsharp
if (Regex.IsMatch("abc 123 @#$", "\\d+")) then printfn "ok"
cpp
if (Regex::IsMatch("abc 123 @#$", "\\d+")) Console::WriteLine("ok");
Loop through a string matching a regex and performing an action for each match
Create a list
[fish1,cow3,boat4] when matching "(fish):1 sausage (cow):3 tree (boat):4" with regex /\((\w+)\):(\d+)/
fsharp
let list = new ResizeArray<string>()
let mutable regmatch = (Regex.Match("(fish):1 sausage (cow):3 tree (boat):4", "\\((\\w+)\\):(\\d+)"))
while regmatch.Success do
list.Add(regmatch.Groups.[1].Captures.[0].ToString() ^ regmatch.Groups.[2].Captures.[0].ToString())
regmatch <- regmatch.NextMatch()
done
for word in list do printfn "%s" word done
let mutable regmatch = (Regex.Match("(fish):1 sausage (cow):3 tree (boat):4", "\\((\\w+)\\):(\\d+)"))
while regmatch.Success do
list.Add(regmatch.Groups.[1].Captures.[0].ToString() ^ regmatch.Groups.[2].Captures.[0].ToString())
regmatch <- regmatch.NextMatch()
done
for word in list do printfn "%s" word done
// A solution without mutation:
let results =
Regex.Matches("(fish):1 sausage (cow):3 tree (boat):4", "\\((\\w+)\\):(\\d+)")
|> Seq.cast
|> Seq.map (fun (regmatch: Match) ->
regmatch.Groups.[1].Captures.[0].ToString() + regmatch.Groups.[2].Captures.[0].ToString()
)
|> List.ofSeq
let results =
Regex.Matches("(fish):1 sausage (cow):3 tree (boat):4", "\\((\\w+)\\):(\\d+)")
|> Seq.cast
|> Seq.map (fun (regmatch: Match) ->
regmatch.Groups.[1].Captures.[0].ToString() + regmatch.Groups.[2].Captures.[0].ToString()
)
|> List.ofSeq
cpp
Match^ match = Regex::Match("(fish):1 sausage (cow):3 tree (boat):4", "\\((\\w+)\\):(\\d+)");
while (match->Success)
{
list->Add(match->Groups[1]->Captures[0]->ToString() + match->Groups[2]->Captures[0]->ToString());
match = match->NextMatch();
}
while (match->Success)
{
list->Add(match->Groups[1]->Captures[0]->ToString() + match->Groups[2]->Captures[0]->ToString());
match = match->NextMatch();
}
Replace the first regex match in a string with a static string
Transform
"Red Green Blue" into "R*d Green Blue" by replacing /e/ with "*"
fsharp
let replaced = ((new Regex("e")).Replace("Red Green Blue", "*", 1))
printfn "%s" replaced
printfn "%s" replaced
cpp
String^ Replaced = (gcnew Regex("e"))->Replace("Red Green Blue", "*", 1);
Replace all regex matches in a string with a static string
Transform
"She sells sea shells" into "She X X shells" by replacing /se\w+/ with "X"
fsharp
let replaced = ((new Regex("se\\w+")).Replace("She sells sea shells", "X"))
printfn "%s" replaced
printfn "%s" replaced
cpp
String^ Replaced = (gcnew Regex("se\\w+"))->Replace("She sells sea shells", "X");
String^ Replaced = Regex::Replace("She sells sea shells", "se\\w+", "X");
Replace all regex matches in a string with a dynamic string
Transform
"The {Quick} Brown {Fox}" into "The kciuQ Brown xoF" by reversing words in braces using the regex /\{(\w+)\}/.
fsharp
open System
open System.Text.RegularExpressions
let reverseMatch (m:Match) =
String(m.Groups.[1].Value.ToCharArray() |> Array.rev)
let output = Regex.Replace("The {Quick} Brown {Fox}", @"\{(\w+)\}", reverseMatch)
open System.Text.RegularExpressions
let reverseMatch (m:Match) =
String(m.Groups.[1].Value.ToCharArray() |> Array.rev)
let output = Regex.Replace("The {Quick} Brown {Fox}", @"\{(\w+)\}", reverseMatch)
cpp
String^ Replaced = (gcnew Regex("{(\\w+)}"))->Replace("The {Quick} Brown {Fox}", gcnew MatchEvaluator(&RegRep::RepGroup));
String^ Replaced = Regex::Replace("The {Quick} Brown {Fox}", "{(\\w+)}", gcnew MatchEvaluator(&RegRep::RepGroup));
Define an empty list
Assign the variable
"list" to a list with no elements
fsharp
let list = []
let list = List.empty
let list = new Generic.List<string>()
let list = new Generic.LinkedList<string>()
cpp
Generic::List<String^>^ list = gcnew Generic::List<String^>();
std::list<std::string> list;
Define a static list
Define the list
[One, Two, Three, Four, Five]
fsharp
let list = ["One"; "Two"; "Three"; "Four"; "Five"]
let list = (new Generic.LinkedList<string>([|"One"; "Two"; "Three"; "Four"; "Five"|]))
let list = (new Generic.LinkedList<string>())
list.AddFirst("One") ; list.AddLast("Five") ; list.AddBefore(list.Find("Five"), "Four")
list.AddAfter(list.Find("One"), "Two") ; list.AddAfter(list.Find("Two"), "Three")
list.AddFirst("One") ; list.AddLast("Five") ; list.AddBefore(list.Find("Five"), "Four")
list.AddAfter(list.Find("One"), "Two") ; list.AddAfter(list.Find("Two"), "Three")
let list = (new Generic.List<string>())
[|"One"; "Two"; "Three"; "Four"; "Five"|] |> Array.iter (fun x -> list.Add(x))
[|"One"; "Two"; "Three"; "Four"; "Five"|] |> Array.iter (fun x -> list.Add(x))
cpp
array<String^>^ input = {"One", "Two", "Three", "Four", "Five"};
Generic::List<String^>^ list = gcnew Generic::List<String^>((Generic::IEnumerable<String^>^) input);
Generic::List<String^>^ list = gcnew Generic::List<String^>((Generic::IEnumerable<String^>^) input);
Generic::List<String^>^ list = gcnew Generic::List<String^>();
list->Add("One");
list->Add("Two");
list->Add("Three");
list->Add("Four");
list->Add("Five");
list->Add("One");
list->Add("Two");
list->Add("Three");
list->Add("Four");
list->Add("Five");
std::string input[] = {"One", "Two", "Three", "Four", "Five"};
std::list<std::string> list(input, input + 5);
std::list<std::string> list(input, input + 5);
std::list<std::string> list;
list.push_back("One");
list.push_back("Two");
list.push_back("Three");
list.push_back("Four");
list.push_back("Five");
list.push_back("One");
list.push_back("Two");
list.push_back("Three");
list.push_back("Four");
list.push_back("Five");
list<string> lst = { "One", "Two", "Three", "Four", "Five" };
list<string> lst;
lst += "One", "Two", "Three", "Four", "Five";
lst += "One", "Two", "Three", "Four", "Five";
Join the elements of a list, separated by commas
Given the list
[Apple, Banana, Carrot] produce "Apple, Banana, Carrot"
fsharp
let result = String.Join(", ", [|"Apple"; "Banana"; "Carrot"|])
let result = (List.fold_left (fun acc item -> acc ^ (", " ^ item)) (List.hd fruit) (List.tl fruit))
let result = (List.fold_left (fun (acc : StringBuilder) (item : string) -> acc.Append(", ").Append(item)) (new StringBuilder(List.hd fruit)) (List.tl fruit)).ToString()
cpp
String^ result = String::Join(L", ", fruit->ToArray());
string fruits[] = {"Apple", "Banana", "Carrot"};
string result = boost::algorithm::join(fruits, ", ");
string result = boost::algorithm::join(fruits, ", ");
Join the elements of a list, in correct english
Create a function join that takes a List and produces a string containing an english language concatenation of the list. It should work with the following examples:
join(
join(
join(
join(
join(
[Apple, Banana, Carrot]) = "Apple, Banana, and Carrot"
join(
[One, Two]) = "One and Two"
join(
[Lonely]) = "Lonely"
join(
[]) = ""
fsharp
let join list =
let rec join' list' s =
match list' with
| [] -> s
| [w] -> join' [] (s ^ " and " ^ w)
| w :: ws -> join' ws (s ^ ", " ^ w)
match list with
| [] -> ""
| w :: ws -> join' ws w
// ------
printfn "%s" (join fruit)
let rec join' list' s =
match list' with
| [] -> s
| [w] -> join' [] (s ^ " and " ^ w)
| w :: ws -> join' ws (s ^ ", " ^ w)
match list with
| [] -> ""
| w :: ws -> join' ws w
// ------
printfn "%s" (join fruit)
cpp
Console::WriteLine(join(fruit));
string join(const vector<string> &s, int b=0)
{
switch (s.size() - b)
{
case 0: return "";
case 1: return s[b];
case 2: return s[b] + (s.size() > 2 ? "," : "") + " and " + s[b+1];
default: return s[b] + ", " + join(s, b+1);
}
}
{
switch (s.size() - b)
{
case 0: return "";
case 1: return s[b];
case 2: return s[b] + (s.size() > 2 ? "," : "") + " and " + s[b+1];
default: return s[b] + ", " + join(s, b+1);
}
}
Produce the combinations from two lists
Given two lists, produce the list of tuples formed by taking the combinations from the individual lists. E.g. given the letters
["a", "b", "c"] and the numbers [4, 5], produce the list: [["a", 4], ["b", 4], ["c", 4], ["a", 5], ["b", 5], ["c", 5]]
fsharp
let combinations = (List.fold_left (fun acc number -> acc @ (List.map (fun letter -> (letter, number)) letters)) [] numbers)
let combinations aa bb =
aa
|> List.map (fun a -> bb |> List.map (fun b -> (a, b)))
|> List.concat
aa
|> List.map (fun a -> bb |> List.map (fun b -> (a, b)))
|> List.concat
cpp
Specialized::StringCollection^ combinations = gcnew Specialized::StringCollection;
for each(int number in numbers)
for each(String^ letter in letters)
combinations->Add(makeCombo(letter, number));
for each(int number in numbers)
for each(String^ letter in letters)
combinations->Add(makeCombo(letter, number));
string letters[] = { "a", "b", "c" };
int numbers[] = { 4, 5 };
list<pair<string,int> > combo;
for (int n = 0; n < sizeof numbers / sizeof *numbers; n++)
for (int l = 0; l < sizeof letters / sizeof *letters; l++)
combo.push_back(make_pair(letters[l], numbers[n]));
cout << combo << endl;
int numbers[] = { 4, 5 };
list<pair<string,int> > combo;
for (int n = 0; n < sizeof numbers / sizeof *numbers; n++)
for (int l = 0; l < sizeof letters / sizeof *letters; l++)
combo.push_back(make_pair(letters[l], numbers[n]));
cout << combo << endl;
From a List Produce a List of Duplicate Entries
Taking a list:
Write the code to produce a list of duplicates in the list:
["andrew", "bob", "chris", "bob"]
Write the code to produce a list of duplicates in the list:
["bob"]
fsharp
["andrew"; "bob"; "chris"; "bob"]
|> Seq.countBy id
|> Seq.filter (fun (k,n) -> n > 1)
|> Seq.map fst
|> Seq.toList
|> Seq.countBy id
|> Seq.filter (fun (k,n) -> n > 1)
|> Seq.map fst
|> Seq.toList
cpp
vector<string> lst = { "andrew", "bob", "chris", "bob" };
vector<string> lst_no_dups;
vector<string> tmp;
vector<string> dups;
sort(lst.begin(), lst.end());
unique_copy(lst.begin(), lst.end(), back_inserter(lst_no_dups));
set_difference(lst.begin(), lst.end(),
lst_no_dups.begin(), lst_no_dups.end(),
back_inserter(tmp));
unique_copy(tmp.begin(), tmp.end(), back_inserter(dups));
cout << dups << endl;
vector<string> lst_no_dups;
vector<string> tmp;
vector<string> dups;
sort(lst.begin(), lst.end());
unique_copy(lst.begin(), lst.end(), back_inserter(lst_no_dups));
set_difference(lst.begin(), lst.end(),
lst_no_dups.begin(), lst_no_dups.end(),
back_inserter(tmp));
unique_copy(tmp.begin(), tmp.end(), back_inserter(dups));
cout << dups << endl;
list<string> lst = { "andrew", "bob", "chris", "bob" };
map<string,int> num_identical;
list<string> dups;
for (auto &s: lst)
num_identical[s]++;
for (auto &n: num_identical)
if (n.second > 1)
dups.push_back(n.first);
cout << dups << endl;
map<string,int> num_identical;
list<string> dups;
for (auto &s: lst)
num_identical[s]++;
for (auto &n: num_identical)
if (n.second > 1)
dups.push_back(n.first);
cout << dups << endl;
Fetch an element of a list by index
Given the list
[One, Two, Three, Four, Five], fetch the third element ('Three')
fsharp
let result = List.nth ["One"; "Two"; "Three"; "Four"; "Five"] 2
cpp
String^ result = list[2];
Fetch the last element of a list
Given the list
[Red, Green, Blue], access the last element ('Blue')
fsharp
let last list =
let rec last' list' =
match list' with
| [x] -> x
| x :: xs -> last' xs
if List.is_empty list then failwith "empty list" else last' list
// ------
let result = last list
let rec last' list' =
match list' with
| [x] -> x
| x :: xs -> last' xs
if List.is_empty list then failwith "empty list" else last' list
// ------
let result = last list
let result = (List.nth list ((List.length list) - 1))
let result = (List.hd (List.rev list))
cpp
String^ result = list[list->Count - 1];
string last_elem = lst.back();
Find the common items in two lists
Given two lists, find the common items. E.g. given beans =
['broad', 'mung', 'black', 'red', 'white'] and colors = ['black', 'red', 'blue', 'green'], what are the bean varieties that are also color names?
fsharp
let beans = (Set.of_list ["broad"; "mung"; "black"; "red"; "white"])
let colors = (Set.of_list ["black"; "red"; "blue"; "green"])
let common = (Set.intersect beans colors)
let colors = (Set.of_list ["black"; "red"; "blue"; "green"])
let common = (Set.intersect beans colors)
let beans = Set ["broad"; "mung"; "black"; "red"; "white"]
let colors = Set ["black"; "red"; "blue"; "green"]
let common = Set.intersect beans colors
let colors = Set ["black"; "red"; "blue"; "green"]
let common = Set.intersect beans colors
// Iterates elements of
// list1 across Elements of list2 returning a list of string options
// as generated by List.tryFind
let findCommon(list1 : 'a list, list2 : 'a list) : 'a list =
list1 |> List.map(fun y -> list2 |> List.tryFind(fun x -> y = x))
// Iterates elements of string option list generated above
// returning a string list containing common elements of List1 and List2
|> List.fold(fun acc x -> if x <> None then x.Value::acc else acc) []
// reverse order of list (can't seem to make List.foldBack work for this
|> List.rev
let beans = ["broad"; "mung"; "black"; "red"; "white"]
let colors = ["black"; "red"; "blue"; "green"]
printfn "%A" (findCommon(beans, colors)) ;;
// list1 across Elements of list2 returning a list of string options
// as generated by List.tryFind
let findCommon(list1 : 'a list, list2 : 'a list) : 'a list =
list1 |> List.map(fun y -> list2 |> List.tryFind(fun x -> y = x))
// Iterates elements of string option list generated above
// returning a string list containing common elements of List1 and List2
|> List.fold(fun acc x -> if x <> None then x.Value::acc else acc) []
// reverse order of list (can't seem to make List.foldBack work for this
|> List.rev
let beans = ["broad"; "mung"; "black"; "red"; "white"]
let colors = ["black"; "red"; "blue"; "green"]
printfn "%A" (findCommon(beans, colors)) ;;
cpp
array<String^>^ inbeans = {"broad", "mung", "black", "red", "white"};
Generic::ICollection<String^>^ beans = makeSET<String^>(gcnew Generic::List<String^>((Generic::IEnumerable<String^>^) inbeans));
array<String^>^ incolors = {"black", "red", "blue", "green"};
Generic::ICollection<String^>^ colors = makeSET<String^>(gcnew Generic::List<String^>((Generic::IEnumerable<String^>^) incolors));
Generic::ICollection<String^>^ result = intersectSET<String^>(beans, colors);
Generic::ICollection<String^>^ beans = makeSET<String^>(gcnew Generic::List<String^>((Generic::IEnumerable<String^>^) inbeans));
array<String^>^ incolors = {"black", "red", "blue", "green"};
Generic::ICollection<String^>^ colors = makeSET<String^>(gcnew Generic::List<String^>((Generic::IEnumerable<String^>^) incolors));
Generic::ICollection<String^>^ result = intersectSET<String^>(beans, colors);
Display the unique items in a list
Display the unique items in a list, e.g. given ages =
[18, 16, 17, 18, 16, 19, 14, 17, 19, 18], display the unique elements, i.e. with duplicates removed.
fsharp
(Set.ofList [18; 16; 17; 18; 16; 19; 14; 17; 19; 18]) |> Set.iter (fun age -> printf "%d, " age)
cpp
array<int>^ input = {18, 16, 17, 18, 16, 19, 14, 17, 19, 18};
Generic::List<int>^ ages = gcnew Generic::List<int>((Generic::IEnumerable<int>^) input);
Generic::ICollection<int>^ result = makeSET<int>(ages);
Generic::List<int>^ ages = gcnew Generic::List<int>((Generic::IEnumerable<int>^) input);
Generic::ICollection<int>^ result = makeSET<int>(ages);
list<int> input;
input += 18, 16, 17, 18, 16, 19, 14, 17, 19, 18;
input.sort();
unique_copy(input.begin(), input.end(), ostream_iterator<int>(cout, "\n"));
input += 18, 16, 17, 18, 16, 19, 14, 17, 19, 18;
input.sort();
unique_copy(input.begin(), input.end(), ostream_iterator<int>(cout, "\n"));
Remove an element from a list by index
Given the list
[Apple, Banana, Carrot], remove the first element to produce the list [Banana, Carrot]
fsharp
let split_at list n =
let rec split_at' list' n' left right =
match list' with
| [] -> (List.rev left, List.rev right)
| x :: xs -> if n' <= n then split_at' xs (n' + 1) (x :: left) right else split_at' xs (n' + 1) left (x :: right)
split_at' list 0 [] []
// ------
let (_, right) = split_at fruit 0
let rec split_at' list' n' left right =
match list' with
| [] -> (List.rev left, List.rev right)
| x :: xs -> if n' <= n then split_at' xs (n' + 1) (x :: left) right else split_at' xs (n' + 1) left (x :: right)
split_at' list 0 [] []
// ------
let (_, right) = split_at fruit 0
let drop list n =
if n <= 0 then
list
else
let (_, right) = split_at list (n - 1)
right
// ------
let result = (drop fruit 1)
if n <= 0 then
list
else
let (_, right) = split_at list (n - 1)
right
// ------
let result = (drop fruit 1)
cpp
fruit->RemoveAt(0);
Remove the last element of a list
fsharp
let take list n =
if n <= 0 then
list
else
let (left, _) = split_at list (n - 1)
left
// ------
let result = (take fruit ((List.length fruit) - 1))
if n <= 0 then
list
else
let (left, _) = split_at list (n - 1)
left
// ------
let result = (take fruit ((List.length fruit) - 1))
let but_last list =
let rec but_last' list' acc =
match list' with
| [x] -> List.rev acc
| x :: xs -> but_last' xs (x :: acc)
if List.is_empty list then [] else but_last' list []
// ------
let result = (but_last fruit)
let rec but_last' list' acc =
match list' with
| [x] -> List.rev acc
| x :: xs -> but_last' xs (x :: acc)
if List.is_empty list then [] else but_last' list []
// ------
let result = (but_last fruit)
cpp
fruit->RemoveAt(fruit->Count - 1);
Rotate a list
Given a list
["apple", "orange", "grapes", "bananas"], rotate it by removing the first item and placing it on the end to yield ["orange", "grapes", "bananas", "apple"]
fsharp
let rotate list n =
if n <= 0 then
list
else
let (left, right) = split_at list (n - 1)
right @ left
// ------
let result = (rotate fruit 1)
if n <= 0 then
list
else
let (left, right) = split_at list (n - 1)
right @ left
// ------
let result = (rotate fruit 1)
cpp
fruit->Add(fruit[0]); fruit->RemoveAt(0);
rotate(fruit.begin(), fruit.begin()+1, fruit.end());
Gather together corresponding elements from multiple lists
Given several lists, gather together the first element from every list, the second element from every list, and so on for all corresponding index values in the lists. E.g. for these three lists, first =
['Bruce', 'Tommy Lee', 'Bruce'], last = ['Willis', 'Jones', 'Lee'], years = [1955, 1946, 1940] the result should produce 3 actors. The middle actor should be Tommy Lee Jones.
fsharp
let result = (List.zip3 first last years)
cpp
array<String^>^ first = {"Bruce", "Tommy Lee", "Bruce"}; array<String^>^ last = {"Willis", "Jones", "Lee"}; array<String^>^ years = {"1955", "1946", "1940"};
array<String^>^ result = zip<String^>(",", first, last, years);
array<String^>^ result = zip<String^>(",", first, last, years);
list<string> first = { "Bruce", "Tommy Lee", "Bruce" };
list<string> last = {"Willis", "Jones", "Lee"};
list<int> years = {1955, 1946, 1940};
list<tuple<string,string,int> > actors;
for (firstIt = first.begin(), lastIt = last.begin(), yearIt = years.begin();
firstIt != first.end() && lastIt != last.end() && yearIt != years.end();
++firstIt, ++lastIt, ++yearIt)
actors.push_back(make_tuple(*firstIt, *lastIt, *yearIt));
list<string> last = {"Willis", "Jones", "Lee"};
list<int> years = {1955, 1946, 1940};
list<tuple<string,string,int> > actors;
for (firstIt = first.begin(), lastIt = last.begin(), yearIt = years.begin();
firstIt != first.end() && lastIt != last.end() && yearIt != years.end();
++firstIt, ++lastIt, ++yearIt)
actors.push_back(make_tuple(*firstIt, *lastIt, *yearIt));
List Combinations
Given two source lists (or sets), generate a list (or set) of all the pairs derived by combining elements from the individual lists (sets). E.g. given suites =
['H', 'D', 'C', 'S'] and faces = ['2', '3', '4', '5', '6', '7', '8', '9', '10', 'J', 'Q', 'K', 'A'], generate the deck of 52 cards, confirm the deck size and check it contains an expected card, say 'Ace of Hearts'.
fsharp
let cards = (List.fold_left (fun acc suite -> acc @ (List.map (fun face -> (suite, face)) faces)) [] suites)
printfn "Deck has %d cards" (List.length cards)
printfn "%s" (if (List.exists (fun e -> e = ("h", "A")) cards) then "Deck contains 'Ace of Hearts'" ; else "'Ace of Hearts' not in deck")
printfn "Deck has %d cards" (List.length cards)
printfn "%s" (if (List.exists (fun e -> e = ("h", "A")) cards) then "Deck contains 'Ace of Hearts'" ; else "'Ace of Hearts' not in deck")
let product (set1 : List<'a>) (set2 : List<'a>) : List<'a * 'a> =
let p = new ResizeArray<'a * 'a>()
for e1 in set1 do for e2 in set2 do p.Add(e1, e2) done done
Array.to_list (p.ToArray())
// ------
let cards = product suites faces
printfn "Deck has %d cards" (List.length cards)
printfn "%s" (if (List.exists (fun e -> e = ("h", "A")) cards) then "Deck contains 'Ace of Hearts'" ; else "'Ace of Hearts' not in deck")
let p = new ResizeArray<'a * 'a>()
for e1 in set1 do for e2 in set2 do p.Add(e1, e2) done done
Array.to_list (p.ToArray())
// ------
let cards = product suites faces
printfn "Deck has %d cards" (List.length cards)
printfn "%s" (if (List.exists (fun e -> e = ("h", "A")) cards) then "Deck contains 'Ace of Hearts'" ; else "'Ace of Hearts' not in deck")
let deck =
suites
|> List.map (fun s -> faces |> List.map (fun f -> (s, f)))
|> List.concat
printfn "Deck has %d cards" (List.length deck)
match deck |> List.exists (fun e -> e = ("h", "A")) with
| true -> printfn "Deck contains 'Ace of Hearts'"
| _ -> printfn "'Ace of Hearts' not in deck"
suites
|> List.map (fun s -> faces |> List.map (fun f -> (s, f)))
|> List.concat
printfn "Deck has %d cards" (List.length deck)
match deck |> List.exists (fun e -> e = ("h", "A")) with
| true -> printfn "Deck contains 'Ace of Hearts'"
| _ -> printfn "'Ace of Hearts' not in deck"
cpp
Specialized::StringCollection^ cards = gcnew Specialized::StringCollection;
for each(String^ suite in suites)
for each(String^ face in faces)
cards->Add(makeCard(suite, face));
Console::WriteLine("Deck has {0} cards", cards.Count);
if (cards->Contains(makeCard("h", "A"))) Console::WriteLine("Deck contains 'Ace of hearts'"); else Console::WriteLine("'Ace of hearts' not in deck");
for each(String^ suite in suites)
for each(String^ face in faces)
cards->Add(makeCard(suite, face));
Console::WriteLine("Deck has {0} cards", cards.Count);
if (cards->Contains(makeCard("h", "A"))) Console::WriteLine("Deck contains 'Ace of hearts'"); else Console::WriteLine("'Ace of hearts' not in deck");
auto suites = {"h", "d", "c", "s"};
auto faces = {"2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A"};
list<card> cards;
for (auto s: suites)
for (auto f: faces)
cards.push_back(make_pair(s,f));
cout << "Deck has " << cards.size() << " cards." << endl;
card ace_of_harts = make_pair("h", "A");
if (end(cards) != find_if(begin(cards), end(cards),
[&](const card& c) { return c == ace_of_harts; }))
cout << "Deck contain 'Ace of Harts'" << endl;
else
cout << "Deck lacks 'Ace of Harts'" << endl;
auto faces = {"2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A"};
list<card> cards;
for (auto s: suites)
for (auto f: faces)
cards.push_back(make_pair(s,f));
cout << "Deck has " << cards.size() << " cards." << endl;
card ace_of_harts = make_pair("h", "A");
if (end(cards) != find_if(begin(cards), end(cards),
[&](const card& c) { return c == ace_of_harts; }))
cout << "Deck contain 'Ace of Harts'" << endl;
else
cout << "Deck lacks 'Ace of Harts'" << endl;
Perform an operation on every item of a list
Perform an operation on every item of a list, e.g.
for the list
the list of sizes of the strings, e.g.
for the list
["ox", "cat", "deer", "whale"] calculate
the list of sizes of the strings, e.g.
[2, 3, 4, 5]
fsharp
let lengths = List.map String.length ["ox"; "cat"; "deer"; "whale"]
cpp
list<string> words;
words.push_back("ox");
words.push_back("cat");
words.push_back("deer");
words.push_back("whale");
for (list<string>::iterator it = words.begin(); it != words.end(); ++it)
cout << it->size() << ' ';
cout << endl;
words.push_back("ox");
words.push_back("cat");
words.push_back("deer");
words.push_back("whale");
for (list<string>::iterator it = words.begin(); it != words.end(); ++it)
cout << it->size() << ' ';
cout << endl;
auto words = { "ox", "cat", "deer", "whale" };
list<size_t> word_sizes;
transform(begin(words),
end(words),
back_inserter(word_sizes),
[](const string& s) { return s.size(); });
list<size_t> word_sizes;
transform(begin(words),
end(words),
back_inserter(word_sizes),
[](const string& s) { return s.size(); });
Split a list of things into numbers and non-numbers
Given a list that might contain e.g. a string, an integer, a float and a date,
split the list into numbers and non-numbers.
split the list into numbers and non-numbers.
fsharp
let (things:obj list) = [ "hello"; 25; 3.14; System.DateTime.Now ]
let isNumber (x:obj) =
match x with
| :? int | :? float | :? byte | :? decimal | :? int16 | :? int64 -> true
| _ -> false
let numbers, nonNumbers = things |> List.partition isNumber
let isNumber (x:obj) =
match x with
| :? int | :? float | :? byte | :? decimal | :? int16 | :? int64 -> true
| _ -> false
let numbers, nonNumbers = things |> List.partition isNumber
cpp
typedef variant<int,float,string,date> dynamic;
class is_number : public static_visitor<bool>
{
public:
bool operator()(int &) const {
return true;
}
bool operator()(float &) const {
return true;
}
bool operator()(string &) const {
return false;
}
bool operator()(date &) const {
return false;
}
};
int main()
{
list<dynamic> lst;
list<dynamic> numbers;
list<dynamic> non_numbers;
lst += "hello", 3.14f, 42, date(2011,Aug,23);
BOOST_FOREACH(dynamic v, lst)
if (apply_visitor(is_number(), v))
numbers += v;
else
non_numbers += v;
class is_number : public static_visitor<bool>
{
public:
bool operator()(int &) const {
return true;
}
bool operator()(float &) const {
return true;
}
bool operator()(string &) const {
return false;
}
bool operator()(date &) const {
return false;
}
};
int main()
{
list<dynamic> lst;
list<dynamic> numbers;
list<dynamic> non_numbers;
lst += "hello", 3.14f, 42, date(2011,Aug,23);
BOOST_FOREACH(dynamic v, lst)
if (apply_visitor(is_number(), v))
numbers += v;
else
non_numbers += v;
#include <iostream>
#include <list>
#include <boost/any.hpp>
#include <boost/date_time/gregorian/gregorian.hpp>
#include <boost/foreach.hpp>
using namespace boost;
using namespace boost::gregorian;
using namespace std;
int main()
{
list<any> lst;
list<any> numbers;
list<any> non_numbers;
lst.push_back(string("hello"));
lst.push_back(42);
lst.push_back(3.14f);
lst.push_back(date(day_clock::local_day()));
BOOST_FOREACH(const any &a, lst)
try
{
numbers.push_back(any_cast<int>(a));
}
catch (bad_any_cast &e)
{
try
{
numbers.push_back(any_cast<float>(a));
}
catch (bad_any_cast &e)
{
non_numbers.push_back(a);
}
}
// float and int are now in 'numbers' and the rest in 'non_numbers'
}
#include <list>
#include <boost/any.hpp>
#include <boost/date_time/gregorian/gregorian.hpp>
#include <boost/foreach.hpp>
using namespace boost;
using namespace boost::gregorian;
using namespace std;
int main()
{
list<any> lst;
list<any> numbers;
list<any> non_numbers;
lst.push_back(string("hello"));
lst.push_back(42);
lst.push_back(3.14f);
lst.push_back(date(day_clock::local_day()));
BOOST_FOREACH(const any &a, lst)
try
{
numbers.push_back(any_cast<int>(a));
}
catch (bad_any_cast &e)
{
try
{
numbers.push_back(any_cast<float>(a));
}
catch (bad_any_cast &e)
{
non_numbers.push_back(a);
}
}
// float and int are now in 'numbers' and the rest in 'non_numbers'
}
Test if a condition holds for all items of a list
Given a list, test if a certain logical condition (i.e. predicate) holds for all items of the list.
fsharp
let rec IsAll predicate source =
let mutable acc = true
for e in source do
acc <- acc && (predicate e)
acc
let mutable acc = true
for e in source do
acc <- acc && (predicate e)
acc
cpp
template <typename InputIterator, typename Predicate>
bool match_all(InputIterator first, InputIterator last, Predicate pred)
{
return find_if(first, last, !pred(_1)) == last;
}
bool match_all(InputIterator first, InputIterator last, Predicate pred)
{
return find_if(first, last, !pred(_1)) == last;
}
Test if a condition holds for any items of a list
Given a list, test if a certain logical condition (i.e. predicate) holds for any items of the list.
fsharp
let rec IsAny predicate source =
match source with
| [] -> false
| h::t ->
if (predicate h) then true
else (IsAny predicate t )
match source with
| [] -> false
| h::t ->
if (predicate h) then true
else (IsAny predicate t )
cpp
template <typename InputIterator, typename Predicate>
bool match_any(InputIterator first, InputIterator last, Predicate pred)
{
return find_if(first, last, pred) != last;
}
bool match_any(InputIterator first, InputIterator last, Predicate pred)
{
return find_if(first, last, pred) != last;
}
Define an empty map
fsharp
let map = Map.empty
let map = new Generic.Dictionary<string, string>()
let map = new Hashtable()
cpp
Hashtable^ hash = gcnew Hashtable;
Generic::Dictionary<String^, String^>^ dict = gcnew Generic::Dictionary<String^, String^>();
std::map<int, std::string> m;
Define an unmodifiable empty map
fsharp
// Most native fsharp data structures are immutable - updating a 'map' sees a modified copy created
let map = Map.empty
let map = Map.empty
cpp
const std::map<T1,T2> immutable_map_instance_of_type_t1_to_t2;
Define an initial map
Define the map
{circle:1, triangle:3, square:4}
fsharp
let shapes = Map.ofList [("circle", 1); ("triangle", 3); ("square", 4)]
let shapes = Map.empty.Add("circle", 1).Add("triangle", 3).Add("square", 4)
let shapes = new Generic.Dictionary<string, int>()
shapes.Add("circle", 1)
shapes.Add("triangle", 3)
shapes.Add("square", 4)
shapes.Add("circle", 1)
shapes.Add("triangle", 3)
shapes.Add("square", 4)
let shapes = Map [("circle", 1); ("triangle", 3); ("square", 4)]
cpp
Hashtable^ shapes = gcnew Hashtable;
shapes->Add("circle", 1);
shapes->Add("triangle", 3);
shapes->Add("square", 4);
shapes->Add("circle", 1);
shapes->Add("triangle", 3);
shapes->Add("square", 4);
Generic::Dictionary<String^, int>^ shapes = gcnew Generic::Dictionary<String^, int>();
shapes->Add("circle", 1);
shapes->Add("triangle", 3);
shapes->Add("square", 4);
shapes->Add("circle", 1);
shapes->Add("triangle", 3);
shapes->Add("square", 4);
map<string, int> shapes;
shapes["circle"] = 1;
shapes["triangle"] = 3;
shapes["square"] = 4;
shapes["circle"] = 1;
shapes["triangle"] = 3;
shapes["square"] = 4;
Check if a key exists in a map
Given a map pets
{joe:cat,mary:turtle,bill:canary} print "ok" if an pet exists for "mary"
fsharp
if (Map.mem "mary" pets) then printfn "ok"
if pets.ContainsKey("mary") then printfn "ok"
cpp
if (pets->ContainsKey("mary")) Console::WriteLine("ok");
if (pets.find("mary") != pets.end()){
std::cout << "ok" << std::endl;
}
std::cout << "ok" << std::endl;
}
if (pets.count("mary") > 0)
cout << "ok" << endl;
cout << "ok" << endl;
Retrieve a value from a map
Given a map pets
{joe:cat,mary:turtle,bill:canary} print the pet for "joe" ("cat")
fsharp
if (Map.mem "joe" pets) then printfn "%s" (Map.find "joe" pets)
if (pets |> Map.exists (fun key _ -> key = "joe")) then printfn "%s" (Map.find "joe" pets)
let key = "joe"
match (pets |> Map.tryfind key) with
| Some(value) -> printfn "%s" value
| None -> printfn "Key %s not found" key
match (pets |> Map.tryfind key) with
| Some(value) -> printfn "%s" value
| None -> printfn "Key %s not found" key
if pets.ContainsKey("joe") then printfn "%s" pets.["joe"]
if pets.ContainsKey("joe") then printfn "%s" (pets.["joe"] :?> string)
cpp
if (pets->ContainsKey("joe")) Console::WriteLine(pets["joe"]);
cout << pets["joe"] << endl;
Add an entry to a map
Given an empty pets map, add the mapping from
"rob" to "dog"
fsharp
pets <- (Map.add "rob" "dog" pets)
pets.Add("rob", "dog")
cpp
pets->Add("rob", "dog");
pets["rob"] = "dog";
Remove an entry from a map
Given a map pets
{joe:cat,mary:turtle,bill:canary} remove the mapping for "bill" and print "canary"
fsharp
let key = "bill"
match (pets |> Map.tryFind key) with
| Some(value) -> pets <- (Map.remove key pets) ; printfn "%s : %s removed" key value
| None -> printfn "Key %s not found" key
match (pets |> Map.tryFind key) with
| Some(value) -> pets <- (Map.remove key pets) ; printfn "%s : %s removed" key value
| None -> printfn "Key %s not found" key
let key = "bill"
let entry = if (pets.ContainsKey(key)) then Some(pets.[key]) ; else None
pets.Remove(key)
match entry with
| Some(value) -> printfn "%s" value
| None -> printfn "key not found"
let entry = if (pets.ContainsKey(key)) then Some(pets.[key]) ; else None
pets.Remove(key)
match entry with
| Some(value) -> printfn "%s" value
| None -> printfn "key not found"
cpp
if (pets->ContainsKey("bill"))
{
String^ value = safe_cast<String^>(pets["bill"]); pets->Remove("bill");
Console::WriteLine("{0}", value);
}
{
String^ value = safe_cast<String^>(pets["bill"]); pets->Remove("bill");
Console::WriteLine("{0}", value);
}
Create a histogram map from a list
Given the list
[a,b,a,c,b,b], produce a map {a:2, b:3, c:1} which contains the count of each unique item in the list
fsharp
let histogram = (List.foldLeft (fun (acc : Map<char, int>) (e : char) -> if (Map.mem e acc) then (Map.add e ((Map.find e acc) + 1) acc) ; else (Map.add e 1 acc)) (Map.empty) list)
let histogram list =
let rec histogram' list' dict' =
match list' with
| [] -> dict'
| x :: xs ->
match Map.tryFind x dict' with
| Some(Value) -> histogram' xs (Map.add x (Value + 1) dict')
| None -> histogram' xs (Map.add x 1 dict')
histogram' list Map.empty
// ------
let histogram' = histogram list
let rec histogram' list' dict' =
match list' with
| [] -> dict'
| x :: xs ->
match Map.tryFind x dict' with
| Some(Value) -> histogram' xs (Map.add x (Value + 1) dict')
| None -> histogram' xs (Map.add x 1 dict')
histogram' list Map.empty
// ------
let histogram' = histogram list
let histogram = (List.foldLeft (fun (acc : Generic.Dictionary<char, int>) (e : char) -> (if acc.ContainsKey(e) then acc.[e] <- acc.[e] + 1 ; else acc.Add(e, 1)) ; acc) (new Generic.Dictionary<char, int>()) list)
let histogram =
list
|> Seq.groupBy (fun a -> a)
|> Seq.map(fun (key, elements) -> key, Seq.length elements)
|> Map.ofSeq
list
|> Seq.groupBy (fun a -> a)
|> Seq.map(fun (key, elements) -> key, Seq.length elements)
|> Map.ofSeq
cpp
for each(String^ entry in input) hash[entry] = hash->ContainsKey(entry)
? Convert::ToInt32(hash[entry]->ToString()) + 1 : 1;
? Convert::ToInt32(hash[entry]->ToString()) + 1 : 1;
for each(String^ entry in input) dict[entry] = dict->ContainsKey(entry) ? dict[entry] + 1 : 1;
map<string,int> hist;
for (auto e: { "a","b","a","c","b","b" })
++hist[e];
for (auto e: hist)
cout << e.first << " : " << e.second << endl;
for (auto e: { "a","b","a","c","b","b" })
++hist[e];
for (auto e: hist)
cout << e.first << " : " << e.second << endl;
Categorise a list
Given the list
[one, two, three, four, five] produce a map {3:[one, two], 4:[four, five], 5:[three]} which sorts elements into map entries based on their length
fsharp
let catmap = (List.foldLeft (fun (acc : Map<int, List<string> >) (e : string) -> if (Map.mem e.Length acc) then (Map.add e.Length ((Map.find e.Length acc) @ [e]) acc) ; else (Map.add e.Length [e] acc)) (Map.empty) list)
let lengthMap =
["one"; "two"; "three"; "four"; "five"]
|> Seq.groupBy (fun s -> s.Length)
|> Seq.map (fun (length, entries) -> (length, entries |> List.ofSeq))
|> Map.ofSeq
["one"; "two"; "three"; "four"; "five"]
|> Seq.groupBy (fun s -> s.Length)
|> Seq.map (fun (length, entries) -> (length, entries |> List.ofSeq))
|> Map.ofSeq
cpp
for each(String^ entry in input)
{
key = entry->Length;
if (!hash->ContainsKey(key)) hash[key] = gcnew ArrayList;
safe_cast<ArrayList^>(hash[key])->Add(entry);
}
{
key = entry->Length;
if (!hash->ContainsKey(key)) hash[key] = gcnew ArrayList;
safe_cast<ArrayList^>(hash[key])->Add(entry);
}
Perform an action if a condition is true (IF .. THEN)
Given a variable name, if the value is
"Bob", display the string "Hello, Bob!". Perform no action if the name is not equal.
fsharp
if name = "Bob" then printfn "Hello, %s!" name
name = "Bob" && begin printfn "Hello, %s!" name ; true end
cpp
if (name == "Bob") Console::WriteLine("Hello, {0}!", name);
if (name == "Bob") std::cout << "Hello, " << name << "!" << std::endl;
Perform different actions depending on a boolean condition (IF .. THEN .. ELSE)
Given a variable age, if the value is greater than 42 display
"You are old", otherwise display "You are young"
fsharp
if age > 42 then printfn "You are old" else printfn "You are young"
let message = if age > 42 then "old" else "young"
printfn "You are %s" message
printfn "You are %s" message
cpp
if (age > 42) Console::WriteLine("You are old");
else Console::WriteLine("You are young");
else Console::WriteLine("You are young");
Console::WriteLine("You are {0}", (age > 42 ? "old" : "young"));
std::printf("You are %s\n", (age > 42 ? "old" : "young"));
Perform different actions depending on several boolean conditions (IF .. THEN .. ELSIF .. ELSE)
fsharp
if age > 84 then printfn "You are really ancient"
elif age > 30 then printfn "You are middle-aged"
else printfn "You are young"
elif age > 30 then printfn "You are middle-aged"
else printfn "You are young"
let message = match age with
| _ when age > 84 -> "really ancient"
| _ when age > 30 -> "middle-aged"
| _ -> "young"
printfn "You are %s" message
| _ when age > 84 -> "really ancient"
| _ when age > 30 -> "middle-aged"
| _ -> "young"
printfn "You are %s" message
cpp
if (age > 84) Console::WriteLine("You are really ancient");
else if (age > 30) Console::WriteLine("You are middle-aged");
else Console::WriteLine("You are young");
else if (age > 30) Console::WriteLine("You are middle-aged");
else Console::WriteLine("You are young");
Console::WriteLine("You are {0}", (age > 84 ? "really ancient" : age > 30 ? "middle-aged" : "young"));
std::cout << "You are " << (age > 84 ? "really ancient" : age > 30 ? "middle-aged" : "young") << std::endl;
Replacing a conditional with many branches with a switch/case statement
Many languages support more compact forms of branching than just if ... then ... else such as switch or case or match. Use such a form to add an appropriate placing suffix to the numbers 1..40, e.g. 1st, 2nd, 3rd, 4th, ..., 11th, 12th, ... 39th, 40th
fsharp
let suffix = function
| n when n > 10 && n < 20 -> "th"
| n when n % 10 = 1 -> "st"
| n when n % 10 = 2 -> "nd"
| n when n % 10 = 3 -> "rd"
| _ -> "th"
seq { 1 .. 40 }
|> Seq.iter (fun n -> printfn "%i%s" n (suffix n))
| n when n > 10 && n < 20 -> "th"
| n when n % 10 = 1 -> "st"
| n when n % 10 = 2 -> "nd"
| n when n % 10 = 3 -> "rd"
| _ -> "th"
seq { 1 .. 40 }
|> Seq.iter (fun n -> printfn "%i%s" n (suffix n))
cpp
#include<iostream.h>
#include<conio.h>
void main()
{
clrscr();
int num,i,x;
cout<<"Enter the range:";
cin>>num;
for(i=1;i<=num;i++)
{
x=i%10;
switch(i)
{
case 11:
case 12:
case 13:cout<<i<<"th ";
continue;
}
switch(x)
{
case 1: cout<<i<<"st ";break;
case 2: cout<<i<<"nd ";break;
case 3: cout<<i<<"rd ";break;
default: cout<<i<<"th ";
}
}
getch();
}
#include<conio.h>
void main()
{
clrscr();
int num,i,x;
cout<<"Enter the range:";
cin>>num;
for(i=1;i<=num;i++)
{
x=i%10;
switch(i)
{
case 11:
case 12:
case 13:cout<<i<<"th ";
continue;
}
switch(x)
{
case 1: cout<<i<<"st ";break;
case 2: cout<<i<<"nd ";break;
case 3: cout<<i<<"rd ";break;
default: cout<<i<<"th ";
}
}
getch();
}
Perform an action multiple times based on a boolean condition, checked before the first action (WHILE .. DO)
Starting with a variable x=1, Print the sequence
"1,2,4,8,16,32,64,128," by doubling x and checking that x is less than 150.
fsharp
let mutable x = 1
while x < 150 do printf "%d, " x ; (x <- x * 2) done
while x < 150 do printf "%d, " x ; (x <- x * 2) done
// The problem is clearly geared towards imperative languages ;-)
// No need to mutate any variable, here's how to do it loop-free functional:
let rec powers2 i = seq { if i < 150 then yield i; yield! powers2 (i*2) }
powers2 1 |> Seq.iter (fun i -> printf "%i, " i)
// No need to mutate any variable, here's how to do it loop-free functional:
let rec powers2 i = seq { if i < 150 then yield i; yield! powers2 (i*2) }
powers2 1 |> Seq.iter (fun i -> printf "%i, " i)
cpp
int x = 1;
while (x < 150) { x *= 2; Console::Write("{0},", x); }
Console::WriteLine();
while (x < 150) { x *= 2; Console::Write("{0},", x); }
Console::WriteLine();
for (int x = 1; x < 150; x *= 2) { std::cout << x << ","; }
std::cout << std::endl;
std::cout << std::endl;
Perform an action multiple times based on a boolean condition, checked after the first action (DO .. WHILE)
Simulate rolling a die until you get a six. Produce random numbers, printing them until a six is rolled. An example output might be
"4,2,1,2,6"
fsharp
open System
let rand = Random()
Seq.initInfinite (fun _ -> rand.Next(1, 7))
|> Seq.takeWhile (fun x -> x < 6)
|> fun items -> String.Join(",", items)
|> function s when s = "" -> printfn "6" | s -> printfn "%s,6" s
let rand = Random()
Seq.initInfinite (fun _ -> rand.Next(1, 7))
|> Seq.takeWhile (fun x -> x < 6)
|> fun items -> String.Join(",", items)
|> function s when s = "" -> printfn "6" | s -> printfn "%s,6" s
cpp
Random^ rnd = gcnew Random;
int dice = rnd->Next(1, 7); Console::Write("{0}", dice);
do { Console::Write(",{0}", (dice = rnd->Next(1, 7))); } while (dice != 6);
Console::WriteLine();
int dice = rnd->Next(1, 7); Console::Write("{0}", dice);
do { Console::Write(",{0}", (dice = rnd->Next(1, 7))); } while (dice != 6);
Console::WriteLine();
Perform an action a fixed number of times (FOR)
Display the string
"Hello" five times like "HelloHelloHelloHelloHello"
fsharp
for i = 1 to 5 do printf "Hello" done
dotimes 5 (fun () -> printf "Hello")
// Repetition via ranging over a List type(index ignored)
for _ in list do printf "Hello" done
for _ in list do printf "Hello" done
// Repetition via ranging over a Sequence type(index ignored)
for _ in sequence do printf "Hello" done
for _ in sequence do printf "Hello" done
// Repetition via ranging over an Array type(index ignored)
for _ in array do printf "Hello" done
for _ in array do printf "Hello" done
cpp
for(int i = 0; i < 5; ++i) Console::Write("Hello");
for(int i = 5; i > 0; --i) Console::Write("Hello");
dotimes(5, hello);
fill_n(ostream_iterator<string>(cout), 5, "Hello");
Perform an action a fixed number of times with a counter
Display the string
"10 .. 9 .. 8 .. 7 .. 6 .. 5 .. 4 .. 3 .. 2 .. 1 .. Liftoff!"
fsharp
for i = 10 downto 1 do printf "%d .. " i done
printfn "Liftoff!"
printfn "Liftoff!"
// Repetition via ranging over a Sequence type
for i in {10 .. -1 .. 1} do printf "%d .. " i done ; printfn "Liftoff!"
for i in {10 .. -1 .. 1} do printf "%d .. " i done ; printfn "Liftoff!"
cpp
for(int i = 10; i != 0; --i) Console::Write("{0} .. ", i);
Console::WriteLine("Liftoff!");
Console::WriteLine("Liftoff!");
Read the contents of a file into a string
fsharp
let file = new FileStream("test.txt", FileMode.Open)
let buffer = new String((new BinaryReader(file)).ReadChars(Convert.ToInt32(file.Length)))
let buffer = new String((new BinaryReader(file)).ReadChars(Convert.ToInt32(file.Length)))
let stream = new StreamReader("test.txt")
let buffer = stream.ReadToEnd()
let buffer = stream.ReadToEnd()
let buffer = File.ReadAllText("test.txt")
cpp
IO::FileStream^ file; String^ buffer;
try
{
file = gcnew IO::FileStream("test.txt", IO::FileMode::Open);
buffer = gcnew String((gcnew IO::BinaryReader(file))->ReadChars(file->Length));
}
try
{
file = gcnew IO::FileStream("test.txt", IO::FileMode::Open);
buffer = gcnew String((gcnew IO::BinaryReader(file))->ReadChars(file->Length));
}
IO::StreamReader^ stream; String^ buffer;
try
{
stream = gcnew IO::StreamReader("test.txt");
buffer = stream->ReadToEnd();
}
try
{
stream = gcnew IO::StreamReader("test.txt");
buffer = stream->ReadToEnd();
}
String^ buffer = IO::File::ReadAllText("test.txt");
Process a file one line at a time
Open the source file to your solution and print each line in the file, prefixed by the line number, like:
1> First line of file
2> Second line of file
3> Third line of file
1> First line of file
2> Second line of file
3> Third line of file
fsharp
let stream = new StreamReader("test.txt")
let mutable i = 1
let mutable line = stream.ReadLine()
while (line <> null) do printfn "%d> %s" i line ; line <- stream.ReadLine() ; i <- i + 1 done
stream.Close()
let mutable i = 1
let mutable line = stream.ReadLine()
while (line <> null) do printfn "%d> %s" i line ; line <- stream.ReadLine() ; i <- i + 1 done
stream.Close()
let proc_a_line (filename : string) proc =
let stream = new StreamReader(filename)
let rec proc_a_line' count line =
match line with
| null -> stream.Close()
| _ -> proc count line ; proc_a_line' (count + 1) (stream.ReadLine())
proc_a_line' 1 (stream.ReadLine())
// ------
let _ = proc_a_line "test.txt" (fun i line -> printfn "%d> %s" i line)
let stream = new StreamReader(filename)
let rec proc_a_line' count line =
match line with
| null -> stream.Close()
| _ -> proc count line ; proc_a_line' (count + 1) (stream.ReadLine())
proc_a_line' 1 (stream.ReadLine())
// ------
let _ = proc_a_line "test.txt" (fun i line -> printfn "%d> %s" i line)
let reader(filename : string) = seq {
use sr = new StreamReader(filename)
while not sr.EndOfStream do
let line = sr.ReadLine()
yield line
done
}
// ------
reader("test.txt") |> Seq.iteri (fun i line -> printfn "%d> %s" (i + 1) line)
use sr = new StreamReader(filename)
while not sr.EndOfStream do
let line = sr.ReadLine()
yield line
done
}
// ------
reader("test.txt") |> Seq.iteri (fun i line -> printfn "%d> %s" (i + 1) line)
File.ReadAllLines("test.txt") |> Array.iteri (fun i line -> printfn "%d> %s" (i + 1) line)
// Unlike ReadAllLines, ReadLines (new in .NET 4) only reads the file
// one line at a time, rather than reading the entire file into an array first.
open System.IO
File.ReadLines("test.txt") |> Seq.iteri (fun i line -> printfn "%d> %s" (i + 1) line)
// one line at a time, rather than reading the entire file into an array first.
open System.IO
File.ReadLines("test.txt") |> Seq.iteri (fun i line -> printfn "%d> %s" (i + 1) line)
cpp
IO::StreamReader^ stream; String^ ln; int i = 0;
try
{
stream = gcnew IO::StreamReader("test.txt");
while ((ln = stream->ReadLine())) Console::WriteLine("{0}> {1}", ++i, ln);
}
try
{
stream = gcnew IO::StreamReader("test.txt");
while ((ln = stream->ReadLine())) Console::WriteLine("{0}> {1}", ++i, ln);
}
int i = 0;
for each(String^ line in IO::File::ReadAllLines("test.txt")) Console::WriteLine("{0}> {1}", ++i, line);
for each(String^ line in IO::File::ReadAllLines("test.txt")) Console::WriteLine("{0}> {1}", ++i, line);
Write a string to a file
fsharp
let stream = new StreamWriter("test.txt", false)
stream.WriteLine("This line overwrites file contents!")
stream.WriteLine("This line overwrites file contents!")
cpp
IO::StreamWriter^ stream;
try
{
stream = gcnew IO::StreamWriter("test.txt", false);
stream->WriteLine("This line overwites file contents!");
}
try
{
stream = gcnew IO::StreamWriter("test.txt", false);
stream->WriteLine("This line overwites file contents!");
}
Append to a file
fsharp
let stream = new StreamWriter("test.txt", true)
stream.WriteLine("This line appended to file!")
stream.WriteLine("This line appended to file!")
cpp
IO::StreamWriter^ stream;
try
{
stream = gcnew IO::StreamWriter("test.txt", true);
stream->WriteLine("This line appended to file!");
}
try
{
stream = gcnew IO::StreamWriter("test.txt", true);
stream->WriteLine("This line appended to file!");
}
Process each file in a directory
fsharp
let dirname = "c:\\"
let processFile filename = printfn "%s" filename
for filename in Directory.GetFiles(dirname) do processFile filename done
let processFile filename = printfn "%s" filename
for filename in Directory.GetFiles(dirname) do processFile filename done
let dirname = "c:\\"
Directory.GetFiles(dirname) |> Array.iter (fun filename -> printfn "%s" filename)
Directory.GetFiles(dirname) |> Array.iter (fun filename -> printfn "%s" filename)
cpp
for each(String^ filename in IO::Directory::GetFiles(dirname)) process(filename);
Process each file in a directory recursively
fsharp
let processDirectory dirname proc =
let rec processDirectory' dirname' =
Directory.GetFiles(dirname') |> Array.iter proc
Directory.GetDirectories(dirname') |> Array.iter processDirectory'
processDirectory' dirname
// ------
let dirname = "c:\\"
processDirectory dirname (fun filename -> printfn "%s" filename)
let rec processDirectory' dirname' =
Directory.GetFiles(dirname') |> Array.iter proc
Directory.GetDirectories(dirname') |> Array.iter processDirectory'
processDirectory' dirname
// ------
let dirname = "c:\\"
processDirectory dirname (fun filename -> printfn "%s" filename)
cpp
void processFile(String^ filename) { Console::WriteLine("{0}", filename); }
void processDirectory(String^ dirname)
{
for each(String^ filename in IO::Directory::GetFiles(dirname)) processFile(filename);
for each(String^ subdirname in IO::Directory::GetDirectories(dirname)) processDirectory(subdirname);
}
int main()
{
processDirectory("c:\\");
}
void processDirectory(String^ dirname)
{
for each(String^ filename in IO::Directory::GetFiles(dirname)) processFile(filename);
for each(String^ subdirname in IO::Directory::GetDirectories(dirname)) processDirectory(subdirname);
}
int main()
{
processDirectory("c:\\");
}
Parse a date and time from a string
Given the string
"2008-05-06 13:29", parse it as a date representing 6th March, 2008 1:29:00pm in the local time zone.
fsharp
let dateTime = DateTimeOffset.Parse("2008-05-06 13:29")
// Use format specifiers to appropriately format string
// 1. Default culture
printfn "%s" (dateTime.ToString("d MMMM, yyyy h:mm:sstt"))
// 2. Nominated culture
Console.WriteLine("{0}", dateTime.ToString("d MMMM, yyyy h:mm:sstt"), Globalization.CultureInfo.CreateSpecificCulture("en-us"))
// Use format specifiers to appropriately format string
// 1. Default culture
printfn "%s" (dateTime.ToString("d MMMM, yyyy h:mm:sstt"))
// 2. Nominated culture
Console.WriteLine("{0}", dateTime.ToString("d MMMM, yyyy h:mm:sstt"), Globalization.CultureInfo.CreateSpecificCulture("en-us"))
let dateTime = DateTimeOffset.Parse("2008-05-06 13:29")
// Customize date/time string
let dsb = ((new StringBuilder(40)).Append(dateTime.ToString("%d")).Append("th ").Append(dateTime.ToString("MMMM, yyyy h:mm:ss")).Append(dateTime.ToString("tt").ToLower()))
printfn "%s" (dsb.ToString())
// Customize date/time string
let dsb = ((new StringBuilder(40)).Append(dateTime.ToString("%d")).Append("th ").Append(dateTime.ToString("MMMM, yyyy h:mm:ss")).Append(dateTime.ToString("tt").ToLower()))
printfn "%s" (dsb.ToString())
cpp
DateTimeOffset^ dateTime = DateTimeOffset::Parse("2008-05-06 13:29");
// Use format specifiers to appropriately format string
// 1. Default culture
Console::WriteLine("{0}", dateTime->ToString("d MMMM, yyyy h:mm:sstt"));
// 2. Nominated culture
Console::WriteLine("{0}", dateTime->ToString("d MMMM, yyyy h:mm:sstt"), Globalization::CultureInfo::CreateSpecificCulture("en-us"));
// Use format specifiers to appropriately format string
// 1. Default culture
Console::WriteLine("{0}", dateTime->ToString("d MMMM, yyyy h:mm:sstt"));
// 2. Nominated culture
Console::WriteLine("{0}", dateTime->ToString("d MMMM, yyyy h:mm:sstt"), Globalization::CultureInfo::CreateSpecificCulture("en-us"));
DateTimeOffset^ dateTime = DateTimeOffset::Parse("2008-05-06 13:29");
// Customize date/time string
Text::StringBuilder^ dsb = gcnew Text::StringBuilder(40);
dsb->Append(dateTime->ToString("%d"))->Append("th ")->Append(dateTime->ToString("MMMM, yyyy h:mm:ss"))->Append(dateTime->ToString("tt")->ToLower());
Console::WriteLine("{0}", dsb);
// Customize date/time string
Text::StringBuilder^ dsb = gcnew Text::StringBuilder(40);
dsb->Append(dateTime->ToString("%d"))->Append("th ")->Append(dateTime->ToString("MMMM, yyyy h:mm:ss"))->Append(dateTime->ToString("tt")->ToLower());
Console::WriteLine("{0}", dsb);
Display information about a date
Display the day of month, day of year, month name and day name of the day 8 days from now.
fsharp
Using F# interactive
> let Then = DateTime.Now.AddDays(8.0)
- let dayNumber = Then.DayOfYear.ToString()
- let solution = Then.ToString("dd " + dayNumber + " MMMM dddd");;
val Then : DateTime = 08/08/2010 08:58:05
val dayNumber : string = "220"
val solution : string = "08 220 August Sunday"
>
> let Then = DateTime.Now.AddDays(8.0)
- let dayNumber = Then.DayOfYear.ToString()
- let solution = Then.ToString("dd " + dayNumber + " MMMM dddd");;
val Then : DateTime = 08/08/2010 08:58:05
val dayNumber : string = "220"
val solution : string = "08 220 August Sunday"
>
cpp
QDate dateEightDaysFromNow = QDate::currentDate().addDays(8);
Display a date in different locales
Display a language/locale friendly version of New Year's Day for 2009 for several languages/locales. E.g. for languages English, French, German, Italian, Dutch the output might be something like:
Thursday, January 1, 2009
jeudi 1 janvier 2009
giovedì 1 gennaio 2009
Donnerstag, 1. Januar 2009
donderdag 1 januari 2009
(Indicate in comments where possible if any language specific or operating system configuration needs to be in place.)
Thursday, January 1, 2009
jeudi 1 janvier 2009
giovedì 1 gennaio 2009
Donnerstag, 1. Januar 2009
donderdag 1 januari 2009
(Indicate in comments where possible if any language specific or operating system configuration needs to be in place.)
fsharp
open System
open System.Globalization
let jan1 = DateTime(2009, 1, 1)
[ "en-US"; "fr-FR"; "de-DE"; "it-IT"; "nl-NL" ]
|> List.map CultureInfo.CreateSpecificCulture
|> List.map (fun c -> jan1.ToString("D", c))
|> List.iter (printfn "%s")
open System.Globalization
let jan1 = DateTime(2009, 1, 1)
[ "en-US"; "fr-FR"; "de-DE"; "it-IT"; "nl-NL" ]
|> List.map CultureInfo.CreateSpecificCulture
|> List.map (fun c -> jan1.ToString("D", c))
|> List.iter (printfn "%s")
cpp
QList<QLocale::Language> locales;
locales << QLocale::English
<< QLocale::French
<< QLocale::German
<< QLocale::Italian
<< QLocale::Dutch;
QDate date(2009, 1, 1);
foreach (QLocale::Language ll, locales)
{
QLocale::setDefault(ll);
qDebug() << date.toString(Qt::DefaultLocaleLongDate);
}
locales << QLocale::English
<< QLocale::French
<< QLocale::German
<< QLocale::Italian
<< QLocale::Dutch;
QDate date(2009, 1, 1);
foreach (QLocale::Language ll, locales)
{
QLocale::setDefault(ll);
qDebug() << date.toString(Qt::DefaultLocaleLongDate);
}
Display the current date and time
Create a Date object representing the current date and time. Print it out.
If you can also do this without creating a Date object you can show that too.
If you can also do this without creating a Date object you can show that too.
fsharp
printfn "%A" System.DateTime.Now
cpp
QDate now = QDate::currentData();
qDebug() << now.toString();
qDebug() << now.toString();
time_t date = time(0);
cout << ctime(&date);
cout << ctime(&date);
Define a class
Declare a class named Greeter that takes a string on creation and greets using this string if you call the
"greet" method.
fsharp
type Greeter(whom' : string) =
member this.greet() = printfn "Hello, %s!" whom'
(new Greeter("world")).greet()
member this.greet() = printfn "Hello, %s!" whom'
(new Greeter("world")).greet()
type Greeter(whom' : string) =
let whom : string = whom'
member this.greet() = printfn "Hello, %s!" whom
(new Greeter("world")).greet()
let whom : string = whom'
member this.greet() = printfn "Hello, %s!" whom
(new Greeter("world")).greet()
type Greeter =
class
val whom : string
new(whom') = { whom = whom' }
member this.greet() = printfn "Hello, %s!" this.whom
end
(new Greeter("world")).greet()
class
val whom : string
new(whom') = { whom = whom' }
member this.greet() = printfn "Hello, %s!" this.whom
end
(new Greeter("world")).greet()
cpp
class Greeter
{
public:
Greeter(const std::string& whom);
void greet() const;
private:
std::string whom;
};
int main()
{
Greeter* gp = new Greeter("world");
gp->greet();
delete gp;
}
Greeter::Greeter(const std::string& whom) : whom(whom) {}
void Greeter::greet() const
{
std::cout << "Hello, " << whom << std::endl;
}
{
public:
Greeter(const std::string& whom);
void greet() const;
private:
std::string whom;
};
int main()
{
Greeter* gp = new Greeter("world");
gp->greet();
delete gp;
}
Greeter::Greeter(const std::string& whom) : whom(whom) {}
void Greeter::greet() const
{
std::cout << "Hello, " << whom << std::endl;
}
public ref class Greeter
{
public:
Greeter(String^ whom);
void greet();
private:
initonly String^ whom;
};
int main()
{
(gcnew Greeter(L"world"))->greet();
}
Greeter::Greeter(String^ whom) : whom(whom) {}
void Greeter::greet()
{
Console::WriteLine(L"Hello, {0}", whom);
}
{
public:
Greeter(String^ whom);
void greet();
private:
initonly String^ whom;
};
int main()
{
(gcnew Greeter(L"world"))->greet();
}
Greeter::Greeter(String^ whom) : whom(whom) {}
void Greeter::greet()
{
Console::WriteLine(L"Hello, {0}", whom);
}
Instantiate object with mutable state
Reimplement the Greeter class so that the
For example, if the greetee is changed to
Hello, Tommy!
The getter would then be used to display the line:
I have just greeted Tommy.
'whom' property or data member remains private but is mutable, and is provided with getter and setter methods. Invoke the setter to change the greetee, invoke 'greet', then use the getter in displaying the line, "I have just greeted {whom}.".
For example, if the greetee is changed to
'Tommy' using the setter, the 'greet' method would display:
Hello, Tommy!
The getter would then be used to display the line:
I have just greeted Tommy.
fsharp
type Greeter(name:string) =
let mutable whom = name
member this.Whom
with get () = whom
and set v = whom <- v
member this.Greet() =
printfn "Hello, %s!" whom
let greeter = Greeter("World")
greeter.Greet()
greeter.Whom <- "Tommy"
greeter.Greet()
printfn "I have just greeted %s." greeter.Whom
let mutable whom = name
member this.Whom
with get () = whom
and set v = whom <- v
member this.Greet() =
printfn "Hello, %s!" whom
let greeter = Greeter("World")
greeter.Greet()
greeter.Whom <- "Tommy"
greeter.Greet()
printfn "I have just greeted %s." greeter.Whom
cpp
#include <iostream>
using namespace std;
class Greeter {
string whom_;
public:
Greeter(const string &whom) : whom_(whom) {}
string get_whom() const {
return whom_;
}
void set_whom(const string &whom) {
whom_ = whom;
}
void greet() const {
cout << "Hello " << whom_ << "!" << endl;
}
};
int main()
{
Greeter greeter("world");
greeter.greet();
greeter.set_whom("Tommy");
greeter.greet();
cout << "I have just greeted " + greeter.get_whom() << "." << endl;
}
using namespace std;
class Greeter {
string whom_;
public:
Greeter(const string &whom) : whom_(whom) {}
string get_whom() const {
return whom_;
}
void set_whom(const string &whom) {
whom_ = whom;
}
void greet() const {
cout << "Hello " << whom_ << "!" << endl;
}
};
int main()
{
Greeter greeter("world");
greeter.greet();
greeter.set_whom("Tommy");
greeter.greet();
cout << "I have just greeted " + greeter.get_whom() << "." << endl;
}
Implement Inheritance Heirarchy
Implement a Shape abstract class which will form the base of an inheritance hierarchy that models 2D geometric shapes. It will have:
* A non-mutable
* A
* A
* A non-mutable
'name' property or data member set by derived or descendant classes at construction time
* A
'area' method intended to be overridden by derived or descendant classes ( double precision floating point return value)
* A
'print' method (also for overriding) will display the shape's name, area, and all shape-specific values
Two derived or descendant classes will be created:
* Circle -> Constructor requires a 'radius' argument, and a 'circumference' method to be implemented
* Rectangle -> Constructor requires 'length' and 'breadth' arguments, and a 'perimeter' method to be implemented
Instantiate an object of each class, and invoke each objects 'print' method to show relevant details.
fsharp
[<AbstractClass>]
type Shape(name:string) =
member this.Name = name
abstract Area : float
abstract Print : unit -> unit
type Circle(name, radius:float) =
inherit Shape(name)
member this.Radius = radius
member this.Circumference =
System.Math.PI * radius * 2.
override this.Area =
System.Math.PI * radius * radius
override this.Print() =
printfn "Circle: %s" this.Name
printfn "Area: %f" this.Area
printfn "Circumference: %f" this.Circumference
printfn "Radius: %f" this.Radius
type Rectangle(name, length:float, breadth:float) =
inherit Shape(name)
member this.Length = length
member this.Breadth = breadth
member this.Perimiter =
(length * 2.) + (breadth * 2.)
override this.Area =
length * breadth
override this.Print() =
printfn "Rectangle: %s" this.Name
printfn "Area: %f" this.Area
printfn "Perimiter: %f" this.Perimiter
printfn "Length: %f" this.Length
printfn "Breadth: %f" this.Breadth
let c = Circle("Foo", 2.1)
let r = Rectangle("Bar", 2.2, 3.3)
c.Print()
printfn ""
r.Print()
type Shape(name:string) =
member this.Name = name
abstract Area : float
abstract Print : unit -> unit
type Circle(name, radius:float) =
inherit Shape(name)
member this.Radius = radius
member this.Circumference =
System.Math.PI * radius * 2.
override this.Area =
System.Math.PI * radius * radius
override this.Print() =
printfn "Circle: %s" this.Name
printfn "Area: %f" this.Area
printfn "Circumference: %f" this.Circumference
printfn "Radius: %f" this.Radius
type Rectangle(name, length:float, breadth:float) =
inherit Shape(name)
member this.Length = length
member this.Breadth = breadth
member this.Perimiter =
(length * 2.) + (breadth * 2.)
override this.Area =
length * breadth
override this.Print() =
printfn "Rectangle: %s" this.Name
printfn "Area: %f" this.Area
printfn "Perimiter: %f" this.Perimiter
printfn "Length: %f" this.Length
printfn "Breadth: %f" this.Breadth
let c = Circle("Foo", 2.1)
let r = Rectangle("Bar", 2.2, 3.3)
c.Print()
printfn ""
r.Print()
cpp
#include <string>
#include <iostream>
using namespace std;
static const double PI = 3.141592;
class Shape {
protected:
string name_;
public:
Shape(const string& name) : name_(name) { }
virtual double area() const = 0;
virtual void print() const = 0;
};
class Circle : public Shape {
double radius_;
public:
Circle(double radius) : Shape("circle"), radius_(radius) { }
double area() const {
return PI * radius_ * radius_;
}
void print() const {
cout << "A " << name_ << " with radius " << radius_ << ", area "
<< area() << " and circumference " << circumference() << "."
<< endl;
}
double circumference() const {
return 2 * PI * radius_;
}
};
class Rectangle : public Shape {
double length_;
double breadth_;
public:
Rectangle(double length, double breadth) :
Shape("rectangle"), length_(length), breadth_(breadth) { }
double area() const {
return length_ * breadth_;
}
void print() const {
cout << "A " << name_ << " with length " << length_ << ", breadth "
<< breadth_ << ", area " << area() << " and perimeter "
<< perimeter() << "." << endl;
}
double perimeter() const {
return 2 * length_ + 2 * breadth_;
}
};
int main(int argc, char *argv[])
{
Circle circle(4);
circle.print();
Rectangle rectangle(2, 5.5);
rectangle.print();
}
#include <iostream>
using namespace std;
static const double PI = 3.141592;
class Shape {
protected:
string name_;
public:
Shape(const string& name) : name_(name) { }
virtual double area() const = 0;
virtual void print() const = 0;
};
class Circle : public Shape {
double radius_;
public:
Circle(double radius) : Shape("circle"), radius_(radius) { }
double area() const {
return PI * radius_ * radius_;
}
void print() const {
cout << "A " << name_ << " with radius " << radius_ << ", area "
<< area() << " and circumference " << circumference() << "."
<< endl;
}
double circumference() const {
return 2 * PI * radius_;
}
};
class Rectangle : public Shape {
double length_;
double breadth_;
public:
Rectangle(double length, double breadth) :
Shape("rectangle"), length_(length), breadth_(breadth) { }
double area() const {
return length_ * breadth_;
}
void print() const {
cout << "A " << name_ << " with length " << length_ << ", breadth "
<< breadth_ << ", area " << area() << " and perimeter "
<< perimeter() << "." << endl;
}
double perimeter() const {
return 2 * length_ + 2 * breadth_;
}
};
int main(int argc, char *argv[])
{
Circle circle(4);
circle.print();
Rectangle rectangle(2, 5.5);
rectangle.print();
}
Implement and use an Interface
Create a Serializable interface consisting of
* Accept a stream or handle or descriptor argument for the source or destination
* Save to destination or restore from source the properties or data members of the implementing class (restrict yourself to the primitive types
Next, create a Person class which has
'save' and 'restore' methods, each of which:
* Accept a stream or handle or descriptor argument for the source or destination
* Save to destination or restore from source the properties or data members of the implementing class (restrict yourself to the primitive types
'int' and 'string')
Next, create a Person class which has
'name' and 'age' properties or data members and implements this interface. Instantiate a Person object, save it to a serial stream, and instantiate a new Person object by restoring it from the serial stream.
fsharp
// Since everyone else is using built-in functionality instead of
// defining an interface as required, I won't buck the trend.
// Maybe this problem should be named "Use serialization features" instead
// of "Implement and use an Interface"
open System
open System.IO
open System.Runtime.Serialization.Formatters.Binary
[<Serializable>]
type Person(name:string, age:int) =
member this.Name = name
member this.Age = age
let serialize x =
use ms = new MemoryStream()
let bf = new BinaryFormatter()
bf.Serialize(ms, x)
ms.ToArray()
let deserialize<'a> bytes =
use ms = new MemoryStream(bytes:byte[])
let bf = new BinaryFormatter()
bf.Deserialize(ms) :?> 'a
let before = Person("Joel", 35)
let bytes = serialize before
let after = deserialize<Person> bytes
printfn "Before: %s, %i" before.Name before.Age
printfn "After: %s, %i" after.Name after.Age
// defining an interface as required, I won't buck the trend.
// Maybe this problem should be named "Use serialization features" instead
// of "Implement and use an Interface"
open System
open System.IO
open System.Runtime.Serialization.Formatters.Binary
[<Serializable>]
type Person(name:string, age:int) =
member this.Name = name
member this.Age = age
let serialize x =
use ms = new MemoryStream()
let bf = new BinaryFormatter()
bf.Serialize(ms, x)
ms.ToArray()
let deserialize<'a> bytes =
use ms = new MemoryStream(bytes:byte[])
let bf = new BinaryFormatter()
bf.Deserialize(ms) :?> 'a
let before = Person("Joel", 35)
let bytes = serialize before
let after = deserialize<Person> bytes
printfn "Before: %s, %i" before.Name before.Age
printfn "After: %s, %i" after.Name after.Age
cpp
struct person
{
person(){}
person(const string &name, int age) : name_(name), age_(age) {}
string name_;
int age_;
template<typename Archive>
void serialize(Archive &ar, const unsigned int version) {
ar & name_ & age_;
}
};
int main()
{
const char *fn = "filename.txt";
person k("Ken", 38);
{
ofstream ofs(fn);
archive::text_oarchive oa(ofs);
oa << k;
}
person restored_person;
{
ifstream ifs(fn);
archive::text_iarchive ia(ifs);
ia >> restored_person;
}
cout << "Name : " << restored_person.name_ << endl
<< "Age : " << restored_person.age_ << endl;
}
{
person(){}
person(const string &name, int age) : name_(name), age_(age) {}
string name_;
int age_;
template<typename Archive>
void serialize(Archive &ar, const unsigned int version) {
ar & name_ & age_;
}
};
int main()
{
const char *fn = "filename.txt";
person k("Ken", 38);
{
ofstream ofs(fn);
archive::text_oarchive oa(ofs);
oa << k;
}
person restored_person;
{
ifstream ifs(fn);
archive::text_iarchive ia(ifs);
ia >> restored_person;
}
cout << "Name : " << restored_person.name_ << endl
<< "Age : " << restored_person.age_ << endl;
}
Check your language appears on the langref.org site
Your language name should appear within the HTML found at the http:
//langreg.org main page.
fsharp
let httpReq = (WebRequest.Create(url) :?> HttpWebRequest)
httpReq.KeepAlive <- false
let httpStream = new StreamReader(httpReq.GetResponse().GetResponseStream())
let htmlPage = httpStream.ReadToEnd()
httpStream.Close()
let offerStatus = (if (htmlPage.IndexOf(url ^ language) > 0) then "offers" ; else "does not offer")
Console.WriteLine("{0} {1} {2}", url, offerStatus, language)
httpReq.KeepAlive <- false
let httpStream = new StreamReader(httpReq.GetResponse().GetResponseStream())
let htmlPage = httpStream.ReadToEnd()
httpStream.Close()
let offerStatus = (if (htmlPage.IndexOf(url ^ language) > 0) then "offers" ; else "does not offer")
Console.WriteLine("{0} {1} {2}", url, offerStatus, language)
cpp
HttpWebRequest^ httpReq = safe_cast<HttpWebRequest^>(WebRequest::Create(url)); httpReq->KeepAlive = false;
StreamReader^ httpStream = gcnew StreamReader(httpReq->GetResponse()->GetResponseStream());
String^ htmlPage = httpStream->ReadToEnd(); httpStream->Close();
Console::WriteLine("{0} {1} {2}", url, (htmlPage->IndexOf(url + language) > 0 ? "offers" : "does not offer"), language);
StreamReader^ httpStream = gcnew StreamReader(httpReq->GetResponse()->GetResponseStream());
String^ htmlPage = httpStream->ReadToEnd(); httpStream->Close();
Console::WriteLine("{0} {1} {2}", url, (htmlPage->IndexOf(url + language) > 0 ? "offers" : "does not offer"), language);
Send an email
Use library functions, classes or objects to create a short email addressed to your own email address. The subject should be,
"Greetings from langref.org", and the user should be prompted for the message body, and whether to cancel or proceed with sending the email.
fsharp
open System
open System.Net
open System.Net.Mail
open System.Net.Mime
let subject = "Greetings from langref.org"
let from = "username@gmail.com"
let destination = "username@gmail.com"
printfn "Write mail body (press 'Enter' when finished):"
let mutable body = Console.ReadLine()
if body = null || body.Length = 0 then
body <- "Hello World"
let mail = new MailMessage(from, destination, subject, body)
let smtpHost = "smtp.gmail.com"
let clientCredentials = new NetworkCredential("username@gmail.com", "password")
let smtpClient = new SmtpClient(smtpHost,587)
smtpClient.EnableSsl <- true
smtpClient.UseDefaultCredentials <- false
smtpClient.Credentials <- clientCredentials
printfn "Send email? y/n"
match Console.ReadLine() with
| "y" -> smtpClient.Send(mail);mail.Dispose();printfn "email delivered"
| "n" -> smtpClient.Dispose()
| _ -> smtpClient.Dispose()
open System.Net
open System.Net.Mail
open System.Net.Mime
let subject = "Greetings from langref.org"
let from = "username@gmail.com"
let destination = "username@gmail.com"
printfn "Write mail body (press 'Enter' when finished):"
let mutable body = Console.ReadLine()
if body = null || body.Length = 0 then
body <- "Hello World"
let mail = new MailMessage(from, destination, subject, body)
let smtpHost = "smtp.gmail.com"
let clientCredentials = new NetworkCredential("username@gmail.com", "password")
let smtpClient = new SmtpClient(smtpHost,587)
smtpClient.EnableSsl <- true
smtpClient.UseDefaultCredentials <- false
smtpClient.Credentials <- clientCredentials
printfn "Send email? y/n"
match Console.ReadLine() with
| "y" -> smtpClient.Send(mail);mail.Dispose();printfn "email delivered"
| "n" -> smtpClient.Dispose()
| _ -> smtpClient.Dispose()
Process an XML document
Given the XML Document:
<shopping>
<item name=
<item name=
</shopping>
Print out the total cost of the items, e.g. $14.50
<shopping>
<item name=
"bread" quantity="3" price="2.50"/>
<item name=
"milk" quantity="2" price="3.50"/>
</shopping>
Print out the total cost of the items, e.g. $14.50
fsharp
#r @"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\v3.5\System.Xml.Linq.dll"
open System
open System.Xml.Linq
//XElement Helper
let xname sname = XName.Get sname
let xmlsnippet =
let snippet = new XElement(xname "shopping")
//create bread
let bread = new XElement(xname "item")
bread.SetAttributeValue(xname "name","bread")
bread.SetAttributeValue(xname "quantity",3)
bread.SetAttributeValue(xname "price",2.50)
//add bread to snippet
snippet.Add(bread)
//create milk
let milk = new XElement(xname "item")
milk.SetAttributeValue(xname "name","milk")
milk.SetAttributeValue(xname "quantity",2)
milk.SetAttributeValue(xname "price",3.50)
//add milk to snippet
snippet.Add(milk)
snippet
let totalprice (xe: XElement) =
xe.Descendants(xname "item")
|> Seq.map(fun i -> Double.Parse(i.Attribute(xname "price").Value))
|> Seq.fold(fun acc x -> acc + x) 0.0
open System
open System.Xml.Linq
//XElement Helper
let xname sname = XName.Get sname
let xmlsnippet =
let snippet = new XElement(xname "shopping")
//create bread
let bread = new XElement(xname "item")
bread.SetAttributeValue(xname "name","bread")
bread.SetAttributeValue(xname "quantity",3)
bread.SetAttributeValue(xname "price",2.50)
//add bread to snippet
snippet.Add(bread)
//create milk
let milk = new XElement(xname "item")
milk.SetAttributeValue(xname "name","milk")
milk.SetAttributeValue(xname "quantity",2)
milk.SetAttributeValue(xname "price",3.50)
//add milk to snippet
snippet.Add(milk)
snippet
let totalprice (xe: XElement) =
xe.Descendants(xname "item")
|> Seq.map(fun i -> Double.Parse(i.Attribute(xname "price").Value))
|> Seq.fold(fun acc x -> acc + x) 0.0
let xname sname = XName.Get sname
let xattr (elem: XElement) sname = elem.Attribute(xname sname).Value
let xml = XDocument.Load("xml.txt")
let shoppingCost =
xml.Descendants(xname "item")
|> Seq.map (fun i -> Double.Parse(xattr i "quantity"), Double.Parse(xattr i "price"))
|> Seq.sumBy (fun (quantity, price) -> quantity * price)
let xattr (elem: XElement) sname = elem.Attribute(xname sname).Value
let xml = XDocument.Load("xml.txt")
let shoppingCost =
xml.Descendants(xname "item")
|> Seq.map (fun i -> Double.Parse(xattr i "quantity"), Double.Parse(xattr i "price"))
|> Seq.sumBy (fun (quantity, price) -> quantity * price)
// Alternative solution that uses XML Navigation, and XPath expressions to ensure that
// the items have the required attributes
let xname sname = XName.Get sname
let xattr (elem: XElement) sname = elem.Attribute(xname sname).Value
let navigator = XPathDocument("xml.txt").CreateNavigator()
let path = XPathExpression.Compile("/shopping/item[@price][@quantity]")
let names = XmlNamespaceManager(navigator.NameTable)
path.SetContext(names)
let shoppingCost =
match path.ReturnType with
| XPathResultType.NodeSet ->
navigator.Select(path)
|> Seq.cast
|> Seq.map (fun (i: XPathNavigator) ->
if i.IsNode then
let elem = XElement.Parse(i.OuterXml)
Double.Parse(xattr elem "quantity"), Double.Parse(xattr elem "price")
else
failwith "Error in expression, expecting to see a node"
)
|> Seq.sumBy (fun (quantity, price) -> quantity * price)
| _ -> failwith "Error in expression, expecting to see a node set"
// the items have the required attributes
let xname sname = XName.Get sname
let xattr (elem: XElement) sname = elem.Attribute(xname sname).Value
let navigator = XPathDocument("xml.txt").CreateNavigator()
let path = XPathExpression.Compile("/shopping/item[@price][@quantity]")
let names = XmlNamespaceManager(navigator.NameTable)
path.SetContext(names)
let shoppingCost =
match path.ReturnType with
| XPathResultType.NodeSet ->
navigator.Select(path)
|> Seq.cast
|> Seq.map (fun (i: XPathNavigator) ->
if i.IsNode then
let elem = XElement.Parse(i.OuterXml)
Double.Parse(xattr elem "quantity"), Double.Parse(xattr elem "price")
else
failwith "Error in expression, expecting to see a node"
)
|> Seq.sumBy (fun (quantity, price) -> quantity * price)
| _ -> failwith "Error in expression, expecting to see a node set"
cpp
char input[] =
"<shopping>"
" <item name=\"bread\" quantity=\"3\" price=\"2.50\"/>"
" <item name=\"milk\" quantity=\"2\" price=\"3.50\"/>"
"</shopping>";
xml_document<> doc;
doc.parse<0>(input);
xml_node<> *shopping = doc.first_node();
float total_price = 0;
for (xml_node<> *item = shopping->first_node(); item != NULL; item = item->next_sibling())
{
float item_sum = 0;
float val;
if (string(item->name()) != "item")
continue;
for (xml_attribute<> *attr = item->first_attribute(); attr != NULL; attr = attr->next_attribute())
{
string name(attr->name());
if (name == "quantity" || name == "price")
{
stringstream v(attr->value());
v >> val;
if (item_sum)
item_sum *= val;
else
item_sum = val;
}
}
total_price += item_sum;
}
cout.setf(ios::fixed, ios::floatfield);
cout << "Total price is $" << setprecision(2) << total_price << endl;
"<shopping>"
" <item name=\"bread\" quantity=\"3\" price=\"2.50\"/>"
" <item name=\"milk\" quantity=\"2\" price=\"3.50\"/>"
"</shopping>";
xml_document<> doc;
doc.parse<0>(input);
xml_node<> *shopping = doc.first_node();
float total_price = 0;
for (xml_node<> *item = shopping->first_node(); item != NULL; item = item->next_sibling())
{
float item_sum = 0;
float val;
if (string(item->name()) != "item")
continue;
for (xml_attribute<> *attr = item->first_attribute(); attr != NULL; attr = attr->next_attribute())
{
string name(attr->name());
if (name == "quantity" || name == "price")
{
stringstream v(attr->value());
v >> val;
if (item_sum)
item_sum *= val;
else
item_sum = val;
}
}
total_price += item_sum;
}
cout.setf(ios::fixed, ios::floatfield);
cout << "Total price is $" << setprecision(2) << total_price << endl;
create some XML programmatically
Given the following CSV:
bread,3,2.50
milk,2,3.50
Produce the equivalent information in XML, e.g.:
<shopping>
<item name=
<item name=
</shopping>
bread,3,2.50
milk,2,3.50
Produce the equivalent information in XML, e.g.:
<shopping>
<item name=
"bread" quantity="3" price="2.50" />
<item name=
"milk" quantity="2" price="3.50" />
</shopping>
fsharp
#r "System.Xml.dll"
#r "System.Xml.Linq.dll"
open System
open System.Xml
open System.Xml.Linq
let data = "bread,3,2.50
milk,2,3.50"
let X name =
XName.Get(name)
let lines = data.Split( [|"\n" |], StringSplitOptions.RemoveEmptyEntries)
let document = new XDocument()
let element = new XElement(X "shopping")
document.Add(element)
lines
|> Seq.iter (fun line ->
let items = line.Split([|','|])
let item = new XElement(X "item",
new XAttribute(X "name", items.[0]),
new XAttribute(X "quantity", items.[1]),
new XAttribute(X "price", items.[2]))
element.Add(item))
let output = document.ToString();;
#r "System.Xml.Linq.dll"
open System
open System.Xml
open System.Xml.Linq
let data = "bread,3,2.50
milk,2,3.50"
let X name =
XName.Get(name)
let lines = data.Split( [|"\n" |], StringSplitOptions.RemoveEmptyEntries)
let document = new XDocument()
let element = new XElement(X "shopping")
document.Add(element)
lines
|> Seq.iter (fun line ->
let items = line.Split([|','|])
let item = new XElement(X "item",
new XAttribute(X "name", items.[0]),
new XAttribute(X "quantity", items.[1]),
new XAttribute(X "price", items.[2]))
element.Add(item))
let output = document.ToString();;
cpp
string input("bread,3,2.50\nmilk,2,3.50\n");
tokenizer<char_separator<char> > tokens(input, char_separator<char>(", \n"));
tokenizer<char_separator<char> >::iterator it = tokens.begin();
xml_document<> doc;
xml_node<> *shopping = doc.allocate_node(node_element, "shopping");
doc.append_node(shopping);
while (it != tokens.end()) {
xml_node<> *item = doc.allocate_node(node_element, "item");
shopping->append_node(item);
item->append_attribute(doc.allocate_attribute("name", doc.allocate_string((*it++).c_str())));
item->append_attribute(doc.allocate_attribute("quantity", doc.allocate_string((*it++).c_str())));
item->append_attribute(doc.allocate_attribute("price", doc.allocate_string((*it++).c_str())));
}
cout << doc << endl;
tokenizer<char_separator<char> > tokens(input, char_separator<char>(", \n"));
tokenizer<char_separator<char> >::iterator it = tokens.begin();
xml_document<> doc;
xml_node<> *shopping = doc.allocate_node(node_element, "shopping");
doc.append_node(shopping);
while (it != tokens.end()) {
xml_node<> *item = doc.allocate_node(node_element, "item");
shopping->append_node(item);
item->append_attribute(doc.allocate_attribute("name", doc.allocate_string((*it++).c_str())));
item->append_attribute(doc.allocate_attribute("quantity", doc.allocate_string((*it++).c_str())));
item->append_attribute(doc.allocate_attribute("price", doc.allocate_string((*it++).c_str())));
}
cout << doc << endl;
Find all Pythagorean triangles with length or height less than or equal to 20
Pythagorean triangles are right angle triangles whose sides comply with the following equation:
a * a + b * b = c * c
where c represents the length of the hypotenuse, and a and b represent the lengths of the other two sides. Find all such triangles where a, b and c are non-zero integers with a and b less than or equal to 20. Sort your results by the size of the hypotenuse. The expected answer is:
a * a + b * b = c * c
where c represents the length of the hypotenuse, and a and b represent the lengths of the other two sides. Find all such triangles where a, b and c are non-zero integers with a and b less than or equal to 20. Sort your results by the size of the hypotenuse. The expected answer is:
[3, 4, 5]
[6, 8, 10]
[5, 12, 13]
[9, 12, 15]
[8, 15, 17]
[12, 16, 20]
[15, 20, 25]
fsharp
let getGoodTri (a,b) =
let h = int(System.Math.Sqrt(float(a*a + b*b)))
if a*a + b*b = h*h then Some(a,b,h)
else None
seq{ for i in 1..20 do yield! seq{for j in i..20 do yield i,j} } |> Seq.choose(getGoodTri) |> Seq.sortBy(fun (_,_,c) -> c);;
let h = int(System.Math.Sqrt(float(a*a + b*b)))
if a*a + b*b = h*h then Some(a,b,h)
else None
seq{ for i in 1..20 do yield! seq{for j in i..20 do yield i,j} } |> Seq.choose(getGoodTri) |> Seq.sortBy(fun (_,_,c) -> c);;
cpp
vector<solution> solutions;
for (int a = 1; a <= 20; ++a)
for (int b = a + 1; b <= 20; ++b)
{
int c_squared = a*a + b*b;
int c = b + 1;
while (c * c < c_squared)
++c;
if (c * c == c_squared)
solutions.push_back(make_tuple(a, b, c));
}
sort(begin(solutions), end(solutions),
[](const solution& s1, const solution& s2) { return get<2>(s1) < get<2>(s2); });
for (const auto &s: solutions)
cout << '[' << get<0>(s) << ", " << get<1>(s) << ", " << get<2>(s) << ']' << endl;
for (int a = 1; a <= 20; ++a)
for (int b = a + 1; b <= 20; ++b)
{
int c_squared = a*a + b*b;
int c = b + 1;
while (c * c < c_squared)
++c;
if (c * c == c_squared)
solutions.push_back(make_tuple(a, b, c));
}
sort(begin(solutions), end(solutions),
[](const solution& s1, const solution& s2) { return get<2>(s1) < get<2>(s2); });
for (const auto &s: solutions)
cout << '[' << get<0>(s) << ", " << get<1>(s) << ", " << get<2>(s) << ']' << endl;
Greatest Common Divisor
Find the largest positive integer that divides two given numbers without a remainder. For example, the GCD of 8 and 12 is 4.
fsharp
let rec gcd x y =
if y = 0 then x
else gcd y (x % y)
if y = 0 then x
else gcd y (x % y)
cpp
#include <iostream>
#include <cstdlib>
#include <algorithm>
using namespace std;
int gcd_recursive(int i, int j) {
if (min(i, j) == 0)
return max(i, j);
else
return gcd_recursive(min(i, j), abs(i - j));
}
int gcd_recursive2(int x, int y) {
if (y == 0)
return x;
else
return gcd_recursive2(y, (x % y));
}
int gcd_iterative(int i, int j) {
while (min(i, j) != 0) {
i = min(i, j);
j = abs(i - j);
}
return max(i, j);
}
int main() {
std::cout << gcd_recursive(8, 12) << std::endl;
std::cout << gcd_recursive2(8, 12) << std::endl;
std::cout << gcd_iterative(8, 12) << std::endl;
return 0;
}
#include <cstdlib>
#include <algorithm>
using namespace std;
int gcd_recursive(int i, int j) {
if (min(i, j) == 0)
return max(i, j);
else
return gcd_recursive(min(i, j), abs(i - j));
}
int gcd_recursive2(int x, int y) {
if (y == 0)
return x;
else
return gcd_recursive2(y, (x % y));
}
int gcd_iterative(int i, int j) {
while (min(i, j) != 0) {
i = min(i, j);
j = abs(i - j);
}
return max(i, j);
}
int main() {
std::cout << gcd_recursive(8, 12) << std::endl;
std::cout << gcd_recursive2(8, 12) << std::endl;
std::cout << gcd_iterative(8, 12) << std::endl;
return 0;
}
produces a copy of its own source code
In computing, a quine is a computer program which produces a copy of its own source code as its only output.
fsharp
(fun s -> printf "%s %s" s s) "(fun s -> printf \"%s %s\" s s)"
cpp
#include <cstdio>
#define B(x) x; printf("{ B(" #x ") }\n");
int main()
{ B(printf("#include <cstdio>\n#define B(x) x; printf(\"{ B(\" #x \") }\\n\");\nint main()\n")) }
#define B(x) x; printf("{ B(" #x ") }\n");
int main()
{ B(printf("#include <cstdio>\n#define B(x) x; printf(\"{ B(\" #x \") }\\n\");\nint main()\n")) }
Subdivide A Problem To A Pool Of Workers (No Shared Data)
Take a hard to compute problem and split it up between multiple worker threads. In your solution, try to fully utilize available cores or processors. (I'm looking at you, Python!)
Note: In this question, there should be no need for shared state between worker threads while the problem is being solved. Only after every thread completes computation are the answers recombined into a single output.
Example:
-Input-
(In python syntax)
In other words, a list of random strings.
-Output-
(In python syntax)
In other words, all possible permutations of each input string are computed.
Note: In this question, there should be no need for shared state between worker threads while the problem is being solved. Only after every thread completes computation are the answers recombined into a single output.
Example:
-Input-
(In python syntax)
["ab", "we", "tfe", "aoj"]
In other words, a list of random strings.
-Output-
(In python syntax)
[ ["ab", "ba", "aa", "bb", "a", "b"], ["we", "ew", "ww", "ee", "w", "e"], ...
In other words, all possible permutations of each input string are computed.
fsharp
open System
let input = [| "ab"; "we"; "tfe"; "aoj" |]
/// Computes all permutations of an array
let rec permute = function
| [| |] -> [| [| |] |]
| a ->
a
|> Array.mapi (fun i ai ->
// Take all elements in the array apart from the i.th, compute
// their permutations, then attach element i at the front of each perm
Array.sub a 0 i
|> Array.append (Array.sub a (i + 1) (a.Length - i - 1))
|> permute
|> Array.map (fun perm -> Array.append [| ai |] perm)
)
|> Array.concat
/// Computes all permutations of a string
let permuteString (s: string) =
s.ToCharArray()
|> permute
|> Array.map (fun p -> new String(p))
let output =
input
|> Array.map (fun word -> async { return (permuteString word) })
|> Async.Parallel
|> Async.RunSynchronously
let input = [| "ab"; "we"; "tfe"; "aoj" |]
/// Computes all permutations of an array
let rec permute = function
| [| |] -> [| [| |] |]
| a ->
a
|> Array.mapi (fun i ai ->
// Take all elements in the array apart from the i.th, compute
// their permutations, then attach element i at the front of each perm
Array.sub a 0 i
|> Array.append (Array.sub a (i + 1) (a.Length - i - 1))
|> permute
|> Array.map (fun perm -> Array.append [| ai |] perm)
)
|> Array.concat
/// Computes all permutations of a string
let permuteString (s: string) =
s.ToCharArray()
|> permute
|> Array.map (fun p -> new String(p))
let output =
input
|> Array.map (fun word -> async { return (permuteString word) })
|> Async.Parallel
|> Async.RunSynchronously
// like the Java and Groovy solutions, does not duplicate letters
open System
open System.Threading.Tasks
let input = [| "ab"; "we"; "tfe"; "aoj" |]
let factorial n =
seq { 1 .. n } |> Seq.reduce (*)
let swap (arr:'a[]) i j =
[| for k = 0 to arr.Length - 1 do
yield if k = i then arr.[j] elif k = j then arr.[i] else arr.[k] |]
let rec permutation (k:int,j:int) (r:'a[]) =
if j = (r.Length + 1) then r
else permutation (k/j+1, j+1) (swap r (j-1) (k%j))
let permutations (source:'a[]) = seq {
for k = 0 to (factorial source.Length) - 1 do
yield permutation (k,2) source
}
let permute (word:string) =
let letters = word.ToCharArray()
permutations letters
|> Seq.map (fun chars -> String(chars))
|> Array.ofSeq
let tasks =
input |> Array.map (fun word -> Task.Factory.StartNew(fun () -> permute word))
let taskResult (t:Task<_>) =
t.Result
let output = Task.Factory.ContinueWhenAll(tasks, fun ts -> Array.map taskResult ts).Result
open System
open System.Threading.Tasks
let input = [| "ab"; "we"; "tfe"; "aoj" |]
let factorial n =
seq { 1 .. n } |> Seq.reduce (*)
let swap (arr:'a[]) i j =
[| for k = 0 to arr.Length - 1 do
yield if k = i then arr.[j] elif k = j then arr.[i] else arr.[k] |]
let rec permutation (k:int,j:int) (r:'a[]) =
if j = (r.Length + 1) then r
else permutation (k/j+1, j+1) (swap r (j-1) (k%j))
let permutations (source:'a[]) = seq {
for k = 0 to (factorial source.Length) - 1 do
yield permutation (k,2) source
}
let permute (word:string) =
let letters = word.ToCharArray()
permutations letters
|> Seq.map (fun chars -> String(chars))
|> Array.ofSeq
let tasks =
input |> Array.map (fun word -> Task.Factory.StartNew(fun () -> permute word))
let taskResult (t:Task<_>) =
t.Result
let output = Task.Factory.ContinueWhenAll(tasks, fun ts -> Array.map taskResult ts).Result
cpp
vector<string> input;
input.push_back("ab");
input.push_back("we");
input.push_back("tfe");
input.push_back("aoj");
// Make the capacity for 'output' the same as 'input'
vector<set<string> > output(input.size());
#pragma omp parallel for
for (int i = 0; i < input.size(); ++i) {
set<string> perms;
generate_perms(input[i], perms);
#pragma omp critical
// Must use operator[]() and not push_back() since this line
// might be called in any order with respect to 'i'
output[i] = perms;
}
cout << output << endl;
input.push_back("ab");
input.push_back("we");
input.push_back("tfe");
input.push_back("aoj");
// Make the capacity for 'output' the same as 'input'
vector<set<string> > output(input.size());
#pragma omp parallel for
for (int i = 0; i < input.size(); ++i) {
set<string> perms;
generate_perms(input[i], perms);
#pragma omp critical
// Must use operator[]() and not push_back() since this line
// might be called in any order with respect to 'i'
output[i] = perms;
}
cout << output << endl;
Subdivide A Problem To A Pool Of Workers (Shared Data)
Take a hard to compute problem and split it up between multiple worker threads. In your solution, try to fully utilize available cores or processors. (I'm looking at you, Python!)
Note: In this question, there should be a need for shared state between worker threads while the problem is being solved.
Example:
-Conway Game of Life-
From Wikipedia:
The universe of the Game of Life is an infinite two-dimensional orthogonal grid of square cells, each of which is in one of two possible states, live or dead. Every cell interacts with its eight neighbors, which are the cells that are directly horizontally, vertically, or diagonally adjacent. At each step in time, the following transitions occur:
1. Any live cell with fewer than two live neighbours dies, as if caused by underpopulation.
2. Any live cell with more than three live neighbours dies, as if by overcrowding.
3. Any live cell with two or three live neighbours lives on to the next generation.
4. Any dead cell with exactly three live neighbours becomes a live cell.
The initial pattern constitutes the seed of the system. The first generation is created by applying the above rules simultaneously to every cell in the seed—births and deaths happen simultaneously, and the discrete moment at which this happens is sometimes called a tick (in other words, each generation is a pure function of the one before). The rules continue to be applied repeatedly to create further generations.
--However, for our purposes, we will assign a size to the game
Notice that in this problem, at each step or
Note: In this question, there should be a need for shared state between worker threads while the problem is being solved.
Example:
-Conway Game of Life-
From Wikipedia:
The universe of the Game of Life is an infinite two-dimensional orthogonal grid of square cells, each of which is in one of two possible states, live or dead. Every cell interacts with its eight neighbors, which are the cells that are directly horizontally, vertically, or diagonally adjacent. At each step in time, the following transitions occur:
1. Any live cell with fewer than two live neighbours dies, as if caused by underpopulation.
2. Any live cell with more than three live neighbours dies, as if by overcrowding.
3. Any live cell with two or three live neighbours lives on to the next generation.
4. Any dead cell with exactly three live neighbours becomes a live cell.
The initial pattern constitutes the seed of the system. The first generation is created by applying the above rules simultaneously to every cell in the seed—births and deaths happen simultaneously, and the discrete moment at which this happens is sometimes called a tick (in other words, each generation is a pure function of the one before). The rules continue to be applied repeatedly to create further generations.
--However, for our purposes, we will assign a size to the game
"board": 2^k * 2^k . That is, the board should be easy to subdivide.
Notice that in this problem, at each step or
"tick", each thread/process will need to share data with its neighborhood.
fsharp
/// Represents a single cell, along with the basic transition rule
type State =
| Alive
| Dead
member this.Transition numLiveNeighbors =
match this with
| Alive when numLiveNeighbors < 2 -> Dead
| Alive when numLiveNeighbors > 3 -> Dead
| Alive -> Alive
| Dead when numLiveNeighbors = 3 -> Alive
| _ -> Dead
member this.ToChar() =
match this with
| Alive -> '*'
| Dead -> ' '
static member OfChar = function
| ' ' -> Dead
| _ -> Alive
type Board (board: State[,]) =
member this.Item
with get(i,j) = board.[i,j]
and set (i,j) v = board.[i,j] <- v
member this.Length1 = Array2D.length1 board
member this.Length2 = Array2D.length2 board
member this.CountLiveNeighbors(i, j) =
[| (-1,-1); (-1,0); (-1,1); (0,-1); (0,1); (1,-1); (1,0); (1,1) |]
|> Array.sumBy (fun (di,dj) ->
if (i + di) > 0 && (i + di) < this.Length1 && (j+dj) > 0 && (j+dj) < this.Length2 then
match board.[i+di,j+dj] with
| Alive -> 1
| _ -> 0
else
0
)
member this.Clone() = Board(Array2D.copy board)
override this.ToString() =
[|
for i in 0 .. this.Length1 - 1 do
let l = [| for j in 0 .. this.Length2 - 1 do yield board.[i,j].ToChar() |]
yield new String(l)
|]
|> String.concat ("\n")
static member OfString (s: string) =
let states =
s.Split('\n')
|> Array.map (fun line -> line.ToCharArray() |> Array.map State.OfChar)
Board (Array2D.init states.Length states.[0].Length (fun i j -> states.[i].[j]))
static member Update (inboard: Board) =
let outboard = inboard.Clone()
let Worker (i1,i2,j1,j2) =
for i in i1 .. i2 do
for j in j1 .. j2 do
outboard.[i,j] <-
inboard.CountLiveNeighbors(i, j)
|> inboard.[i,j].Transition
let N1 = inboard.Length1 / 2
let N2 = inboard.Length2 / 2
[| (0,N1,0,N2); (N1+1,inboard.Length1-1,0,N2); (0,N1,N2+1,inboard.Length2-1); (N1+1,inboard.Length1-1,N2+1,inboard.Length2-1) |]
|> Array.map (fun bounds -> async { Worker bounds})
|> Async.Parallel
|> Async.RunSynchronously
|> ignore
outboard
let blinker = " \n * \n * \n * \n " |> Board.OfString
do
let after1cycles =
blinker
|> Board.Update
let after3cycles =
after1cycles
|> Board.Update
|> Board.Update
printfn "%s" (after3cycles.ToString())
type State =
| Alive
| Dead
member this.Transition numLiveNeighbors =
match this with
| Alive when numLiveNeighbors < 2 -> Dead
| Alive when numLiveNeighbors > 3 -> Dead
| Alive -> Alive
| Dead when numLiveNeighbors = 3 -> Alive
| _ -> Dead
member this.ToChar() =
match this with
| Alive -> '*'
| Dead -> ' '
static member OfChar = function
| ' ' -> Dead
| _ -> Alive
type Board (board: State[,]) =
member this.Item
with get(i,j) = board.[i,j]
and set (i,j) v = board.[i,j] <- v
member this.Length1 = Array2D.length1 board
member this.Length2 = Array2D.length2 board
member this.CountLiveNeighbors(i, j) =
[| (-1,-1); (-1,0); (-1,1); (0,-1); (0,1); (1,-1); (1,0); (1,1) |]
|> Array.sumBy (fun (di,dj) ->
if (i + di) > 0 && (i + di) < this.Length1 && (j+dj) > 0 && (j+dj) < this.Length2 then
match board.[i+di,j+dj] with
| Alive -> 1
| _ -> 0
else
0
)
member this.Clone() = Board(Array2D.copy board)
override this.ToString() =
[|
for i in 0 .. this.Length1 - 1 do
let l = [| for j in 0 .. this.Length2 - 1 do yield board.[i,j].ToChar() |]
yield new String(l)
|]
|> String.concat ("\n")
static member OfString (s: string) =
let states =
s.Split('\n')
|> Array.map (fun line -> line.ToCharArray() |> Array.map State.OfChar)
Board (Array2D.init states.Length states.[0].Length (fun i j -> states.[i].[j]))
static member Update (inboard: Board) =
let outboard = inboard.Clone()
let Worker (i1,i2,j1,j2) =
for i in i1 .. i2 do
for j in j1 .. j2 do
outboard.[i,j] <-
inboard.CountLiveNeighbors(i, j)
|> inboard.[i,j].Transition
let N1 = inboard.Length1 / 2
let N2 = inboard.Length2 / 2
[| (0,N1,0,N2); (N1+1,inboard.Length1-1,0,N2); (0,N1,N2+1,inboard.Length2-1); (N1+1,inboard.Length1-1,N2+1,inboard.Length2-1) |]
|> Array.map (fun bounds -> async { Worker bounds})
|> Async.Parallel
|> Async.RunSynchronously
|> ignore
outboard
let blinker = " \n * \n * \n * \n " |> Board.OfString
do
let after1cycles =
blinker
|> Board.Update
let after3cycles =
after1cycles
|> Board.Update
|> Board.Update
printfn "%s" (after3cycles.ToString())
Create a multithreaded "Hello World"
Create a program which outputs the string
Example:
-Output-
Thread one says Hello World!
Thread two says Hello World!
Thread four says Hello World!
Thread three says Hello World!
-Notice that the threads can print in any order.
"Hello World" to the console, multiple times, using separate threads or processes.
Example:
-Output-
Thread one says Hello World!
Thread two says Hello World!
Thread four says Hello World!
Thread three says Hello World!
-Notice that the threads can print in any order.
fsharp
let mappedString =
["Thread one says Hello World!";
"Thread two says Hello World!";
"Thread four says Hello World!";
"Thread three says Hello World!"]
|> Seq.map (fun str -> async { printfn "%s" str })
Async.RunSynchronously (Async.Parallel mappedString)
["Thread one says Hello World!";
"Thread two says Hello World!";
"Thread four says Hello World!";
"Thread three says Hello World!"]
|> Seq.map (fun str -> async { printfn "%s" str })
Async.RunSynchronously (Async.Parallel mappedString)
cpp
#include <iostream>
#include <string>
using namespace std;
int main(){
int pid;
string text[4]={"one","two","three","four"};
for (int i=0;i<4;i++){
pid=fork();
if (pid>0){
//cout << "Process("<<pid<<") - " << "Thread " << text[i] << " says Hello World!" << endl;
cout << "Thread " << text[i] << " says Hello World!" << endl;
exit(0);
}
}
return 0;
}
#include <string>
using namespace std;
int main(){
int pid;
string text[4]={"one","two","three","four"};
for (int i=0;i<4;i++){
pid=fork();
if (pid>0){
//cout << "Process("<<pid<<") - " << "Thread " << text[i] << " says Hello World!" << endl;
cout << "Thread " << text[i] << " says Hello World!" << endl;
exit(0);
}
}
return 0;
}
#include <iostream>
#include <string>
#include <omp.h>
int main() {
unsigned int const num_threads = 4;
std::string const names[] = { "one", "two", "three", "four" };
# pragma omp parallel num_threads(num_threads)
{
unsigned const id = omp_get_thread_num();
// Stream concatenation isn't thread-safe so we use a critical section.
# pragma omp critical
std::cout << "Thread " << names[id] << " says Hello World!" << std::endl;
}
}
#include <string>
#include <omp.h>
int main() {
unsigned int const num_threads = 4;
std::string const names[] = { "one", "two", "three", "four" };
# pragma omp parallel num_threads(num_threads)
{
unsigned const id = omp_get_thread_num();
// Stream concatenation isn't thread-safe so we use a critical section.
# pragma omp critical
std::cout << "Thread " << names[id] << " says Hello World!" << std::endl;
}
}
Create read/write lock on a shared resource.
Create multiple threads or processes who are either readers or writers. There should be more readers then writers.
(From Wikipedia):
Multiple readers can read the data in parallel but an exclusive lock is needed while writing the data. When a writer is writing the data, readers will be blocked until the writer is finished writing.
Example:
-Output-
Thread one says that the value is 8.
Thread three says that the value is 8.
Thread two is taking the lock.
Thread four tried to read the value, but could not.
Thread five tried to write to the value, but could not.
Thread two is changing the value to 9.
Thread two is releasing the lock.
Thread four says that the value is 9.
...
--Notice that when a needed resource is locked, a thread can set a timer and try again in the future, or wait to be notified that the resource is no longer locked.
(From Wikipedia):
Multiple readers can read the data in parallel but an exclusive lock is needed while writing the data. When a writer is writing the data, readers will be blocked until the writer is finished writing.
Example:
-Output-
Thread one says that the value is 8.
Thread three says that the value is 8.
Thread two is taking the lock.
Thread four tried to read the value, but could not.
Thread five tried to write to the value, but could not.
Thread two is changing the value to 9.
Thread two is releasing the lock.
Thread four says that the value is 9.
...
--Notice that when a needed resource is locked, a thread can set a timer and try again in the future, or wait to be notified that the resource is no longer locked.
fsharp
open System.Threading
let lock = new ReaderWriterLock()
let mutable value = 0
let lockTimeout = 1
let ReaderThread t =
let random = new System.Random()
for i in 0 .. 100 do
try
lock.AcquireReaderLock(lockTimeout)
try
printfn "Thread %i says that the value is %i" t value
finally
lock.ReleaseReaderLock()
with _ ->
printfn "Thread %i tried to read the value, but could not (timeout)." t
Thread.Sleep(random.Next(50))
let WriterThread t =
let random = new System.Random()
for i in 0 .. 100 do
try
lock.AcquireWriterLock(lockTimeout)
try
value <- random.Next(10)
printfn "Thread %i is changing the value to %i" t value
Thread.MemoryBarrier()
finally
lock.ReleaseWriterLock()
printfn "Thread %i is releasing the lock." t
with _ ->
printfn "Thread %i tried to write the value, but could not (timeout)." t
Thread.Sleep(random.Next(50))
[| 0 .. 20 |]
|> Array.iter (fun t ->
async {
if t % 3 = 0 then
WriterThread t
else
ReaderThread t
}
|> Async.Start
)
let lock = new ReaderWriterLock()
let mutable value = 0
let lockTimeout = 1
let ReaderThread t =
let random = new System.Random()
for i in 0 .. 100 do
try
lock.AcquireReaderLock(lockTimeout)
try
printfn "Thread %i says that the value is %i" t value
finally
lock.ReleaseReaderLock()
with _ ->
printfn "Thread %i tried to read the value, but could not (timeout)." t
Thread.Sleep(random.Next(50))
let WriterThread t =
let random = new System.Random()
for i in 0 .. 100 do
try
lock.AcquireWriterLock(lockTimeout)
try
value <- random.Next(10)
printfn "Thread %i is changing the value to %i" t value
Thread.MemoryBarrier()
finally
lock.ReleaseWriterLock()
printfn "Thread %i is releasing the lock." t
with _ ->
printfn "Thread %i tried to write the value, but could not (timeout)." t
Thread.Sleep(random.Next(50))
[| 0 .. 20 |]
|> Array.iter (fun t ->
async {
if t % 3 = 0 then
WriterThread t
else
ReaderThread t
}
|> Async.Start
)
cpp
class reader
{
string name_;
public:
reader(const string& name) : name_(name) {}
void operator()() {
for (;;this_thread::sleep(posix_time::milliseconds(1)))
{
shared_lock<shared_mutex> lock(m, try_to_lock);
lock_guard<mutex> cout_lock(io_m);
cout << "Thread " << name_;
if (lock)
cout << " says that the value is " << shared_value << "." << endl;
else
cout << " tried to read the value, but could not." << endl;
}
}
};
class writer
{
string name_;
public:
writer(const string& name) : name_(name) {}
void operator()() {
for (;;this_thread::sleep(posix_time::milliseconds(1)))
{
unique_lock<shared_mutex> lock(m, try_to_lock);
lock_guard<mutex> cout_lock(io_m);
cout << "Thread " << name_;
if (lock)
{
cout << " is taking the lock." << endl;
shared_value = rand() % 10;
cout << "Thread " << name_ << " is changing the value to " << shared_value << endl;
cout << "Thread " << name_ << " is releasing the lock. " << endl;
}
else
cout << " tried to write to the value, but could not." << endl;
}
}
};
int main()
{
thread t1 = thread(reader("one"));
thread t2 = thread(reader("two"));
thread t3 = thread(reader("three"));
thread t4 = thread(writer("four"));
writer("five")();
}
{
string name_;
public:
reader(const string& name) : name_(name) {}
void operator()() {
for (;;this_thread::sleep(posix_time::milliseconds(1)))
{
shared_lock<shared_mutex> lock(m, try_to_lock);
lock_guard<mutex> cout_lock(io_m);
cout << "Thread " << name_;
if (lock)
cout << " says that the value is " << shared_value << "." << endl;
else
cout << " tried to read the value, but could not." << endl;
}
}
};
class writer
{
string name_;
public:
writer(const string& name) : name_(name) {}
void operator()() {
for (;;this_thread::sleep(posix_time::milliseconds(1)))
{
unique_lock<shared_mutex> lock(m, try_to_lock);
lock_guard<mutex> cout_lock(io_m);
cout << "Thread " << name_;
if (lock)
{
cout << " is taking the lock." << endl;
shared_value = rand() % 10;
cout << "Thread " << name_ << " is changing the value to " << shared_value << endl;
cout << "Thread " << name_ << " is releasing the lock. " << endl;
}
else
cout << " tried to write to the value, but could not." << endl;
}
}
};
int main()
{
thread t1 = thread(reader("one"));
thread t2 = thread(reader("two"));
thread t3 = thread(reader("three"));
thread t4 = thread(writer("four"));
writer("five")();
}
Separate user interaction and computation.
Allow your program to accept user interaction while conducting a long running computation.
Example:
Hello user! Please input a string to permute: (input thread)
abcdef
Passing on abcdef... (input thread)
Please input another string to permute: (input thread)
lol
Passing on lol... (input thread)
Done Work On abcdef! (worker thread)
Please input another string to permute: (input thread)
EXIT
Quitting, I
--Notice, that this could be accomplished on the command line or within a GUI. The point is that computation and user interaction should take place on separate threads of control.
Example:
Hello user! Please input a string to permute: (input thread)
abcdef
Passing on abcdef... (input thread)
Please input another string to permute: (input thread)
lol
Passing on lol... (input thread)
Done Work On abcdef! (worker thread)
["abcdef", "abcefd", ... ] (worker thread)
Please input another string to permute: (input thread)
EXIT
Quitting, I
'll let my worker thread know... (input thread)
We're quitting! Alright! (worker thread)
--Notice, that this could be accomplished on the command line or within a GUI. The point is that computation and user interaction should take place on separate threads of control.
fsharp
open System
/// Computes all permutations of an array
let rec permute = function
| [| |] -> [| [| |] |]
| a ->
a
|> Array.mapi (fun i ai ->
Array.sub a 0 i
|> Array.append (Array.sub a (i + 1) (a.Length - i - 1))
|> permute
|> Array.map (fun perm -> Array.append [| ai |] perm)
)
|> Array.concat
/// Computes all permutations of a string
let permuteString (s: string) =
s.ToCharArray()
|> permute
|> Array.map (fun p -> new String(p))
type PermuteMessage =
| PermuteString of string
| Cancel
let mailbox = new MailboxProcessor<PermuteMessage>(fun inbox ->
let rec loop() =
async {
let! msg = inbox.Receive()
match msg with
| PermuteString s ->
printfn "[Worker] Starting to work on %s" s
let p = permuteString s
printfn "[Worker] Done my work on %s" s
let firstElems =
if s.Length > 4 then
let first = p |> Seq.truncate 4 |> Seq.toArray
String.Join(", ", first) + ", ..."
else
String.Join(", ", p)
printfn "[Worker] Result is %s" firstElems
return! loop()
| Cancel ->
printfn "[Worker] Nuff done, I'm quitting!"
return ()
}
loop()
)
do
printfn "[Input] Setting up worker."
mailbox.Start()
let loop = ref true
while !loop do
printfn "[Input] Please enter a word, or EXIT to exit"
let s = Console.ReadLine()
match s with
| "EXIT" ->
printfn "[Input] Sending worker the cancellation notice."
mailbox.Post(Cancel)
loop := false
| _ ->
printfn "[Input] Sending task to the worker."
mailbox.Post(PermuteString s)
/// Computes all permutations of an array
let rec permute = function
| [| |] -> [| [| |] |]
| a ->
a
|> Array.mapi (fun i ai ->
Array.sub a 0 i
|> Array.append (Array.sub a (i + 1) (a.Length - i - 1))
|> permute
|> Array.map (fun perm -> Array.append [| ai |] perm)
)
|> Array.concat
/// Computes all permutations of a string
let permuteString (s: string) =
s.ToCharArray()
|> permute
|> Array.map (fun p -> new String(p))
type PermuteMessage =
| PermuteString of string
| Cancel
let mailbox = new MailboxProcessor<PermuteMessage>(fun inbox ->
let rec loop() =
async {
let! msg = inbox.Receive()
match msg with
| PermuteString s ->
printfn "[Worker] Starting to work on %s" s
let p = permuteString s
printfn "[Worker] Done my work on %s" s
let firstElems =
if s.Length > 4 then
let first = p |> Seq.truncate 4 |> Seq.toArray
String.Join(", ", first) + ", ..."
else
String.Join(", ", p)
printfn "[Worker] Result is %s" firstElems
return! loop()
| Cancel ->
printfn "[Worker] Nuff done, I'm quitting!"
return ()
}
loop()
)
do
printfn "[Input] Setting up worker."
mailbox.Start()
let loop = ref true
while !loop do
printfn "[Input] Please enter a word, or EXIT to exit"
let s = Console.ReadLine()
match s with
| "EXIT" ->
printfn "[Input] Sending worker the cancellation notice."
mailbox.Post(Cancel)
loop := false
| _ ->
printfn "[Input] Sending task to the worker."
mailbox.Post(PermuteString s)
cpp
class bg_worker
{
mutex bg_mutex_;
condition_variable work_present_;
deque<string> work_queue_;
result calc_perm(string s) {
result perms = result(new list<string>());
// sleep to simulate lots of work...
this_thread::sleep(posix_time::seconds(3));
sort(s.begin(), s.end());
do {
perms->push_back(s);
} while (next_permutation(s.begin(), s.end()));
return perms;
}
public:
void submit_work(const string &s) {
lock_guard<mutex> lock(bg_mutex_);
work_queue_.push_back(s);
work_present_.notify_one();
}
void operator()() {
for (;;) {
unique_lock<mutex> lock(bg_mutex_);
while (work_queue_.empty())
work_present_.wait(lock);
string s = work_queue_.front();
work_queue_.pop_front();
lock.unlock();
if (s == "EXIT") {
lock_guard<mutex> cout_lock(cout_mutex);
cout << "We're quitting! Alright!" << endl;
break;
}
result perm = calc_perm(s);
lock_guard<mutex> cout_lock(cout_mutex);
cout << "Done Work On " << s << "!" << endl;
cout << perm << endl;
}
}
};
int main()
{
bg_worker worker;
thread bg_thr(boost::ref(worker));
bool done = false;
{
lock_guard<mutex> cout_lock(cout_mutex);
cout << "Hello user! Please input a string to permute:" << endl;
}
while (!done)
{
string input;
cin >> input;
{
lock_guard<mutex> cout_lock(cout_mutex);
if (input == "EXIT") {
cout << "Quitting, I'll let my worker thread know..." << endl;
done = true;
} else {
cout << "Passing on " << input << "..." << endl;
cout << "Please input another string to permute:" << endl;
}
}
worker.submit_work(input);
}
bg_thr.join();
}
{
mutex bg_mutex_;
condition_variable work_present_;
deque<string> work_queue_;
result calc_perm(string s) {
result perms = result(new list<string>());
// sleep to simulate lots of work...
this_thread::sleep(posix_time::seconds(3));
sort(s.begin(), s.end());
do {
perms->push_back(s);
} while (next_permutation(s.begin(), s.end()));
return perms;
}
public:
void submit_work(const string &s) {
lock_guard<mutex> lock(bg_mutex_);
work_queue_.push_back(s);
work_present_.notify_one();
}
void operator()() {
for (;;) {
unique_lock<mutex> lock(bg_mutex_);
while (work_queue_.empty())
work_present_.wait(lock);
string s = work_queue_.front();
work_queue_.pop_front();
lock.unlock();
if (s == "EXIT") {
lock_guard<mutex> cout_lock(cout_mutex);
cout << "We're quitting! Alright!" << endl;
break;
}
result perm = calc_perm(s);
lock_guard<mutex> cout_lock(cout_mutex);
cout << "Done Work On " << s << "!" << endl;
cout << perm << endl;
}
}
};
int main()
{
bg_worker worker;
thread bg_thr(boost::ref(worker));
bool done = false;
{
lock_guard<mutex> cout_lock(cout_mutex);
cout << "Hello user! Please input a string to permute:" << endl;
}
while (!done)
{
string input;
cin >> input;
{
lock_guard<mutex> cout_lock(cout_mutex);
if (input == "EXIT") {
cout << "Quitting, I'll let my worker thread know..." << endl;
done = true;
} else {
cout << "Passing on " << input << "..." << endl;
cout << "Please input another string to permute:" << endl;
}
}
worker.submit_work(input);
}
bg_thr.join();
}
Put a internationalizate of HelloWorld program
Set locale to
In pseudocode:
Void main ()
"es" (spanish) and provide a program that changes outputs ("Helloworld") depending of locale.
In pseudocode:
Void main ()
{
Locale.set("es")
print.translate("Helloworld, Locale.get)
}
180
"http://www.ecigarettefresh.com/cartomizer-ecigarette-c-7.html ">Cartomizer E-Cigarette<
/a>strong>"http://www.ecigarettefresh.com/cartomizer-ecigarette-c-7.html ">Electronic Cigarette<
/a>strong>"http://www.ecigarettefresh.com/cartomizer-ecigarette-c-7.html ">Smokeless Cigarettes<
/a>strong>"http://www.ecigarettefresh.com/cartomizer-ecigarette-c-7.html ">discount Electronic Cigarette<
/a>strong>"http://www.ecigarettefresh.com/disposable-ecigarette-c-8.html ">Disposable E-Cigarette<
/a>strong>"http://www.ecigarettefresh.com/accessories-c-6.html ">Accessories<
/a>strong>"http://www.ecigarettefresh.com/mini-ecigarette-c-13.html ">Mini E-cigarette<
/a>strong>"http://www.ecigarettefresh.com/esmoking-c-11.html ">electric cigarette outlet<
/a>strong>"http://www.ecigarettefresh.com/smokeless-cigarettes-c-12.html ">Smokeless Cigarettes online<
/a>strong>"http://www.ecigarettefresh.com/ecigarette-c-9.html ">Electronic Cigarette online<
/a>strong>. "http://blog.allluxurywatches.com"> outlet blog <
/a>
outlet a>"http://blog.linksoflondonshopping.com"> About ecigarettefresh.com blog
180
"http://www.lovembtshoes.com/ ">mbt boots<
/a>strong>"http://www.lovembtshoes.com/ ">mbt shoes<
/a>strong>"http://www.lovembtshoes.com/ ">buy mbt boots<
/a>strong>"http://www.lovembtshoes.com/ ">discount mbt shoes<
/a>strong>"http://www.lovembtshoes.com/ ">mbt shoes online<
/a>strong>"http://www.lovembtshoes.com/mbt-tariki-c-50.html ">MBT Tariki shoes outlet<
/a>strong>"http://www.lovembtshoes.com/mbt-karibu-c-18.html ">wholesale MBT Karibu shoes<
/a>strong>"http://www.lovembtshoes.com/mbt-kafala-black-leather-women-shoes-p-68.html ">buy MBT Kafala shoes<
/a>strong>"http://www.lovembtshoes.com/mbt-meli-c-33.html ">MBT Meli<
/a>strong>"http://www.lovembtshoes.com/mbt-kifundo-c-25.html ">discount MBT Kifundo<
/a>strong>. "http://blog.bootsonlinecompany.com"> Bia blog <
/a>
Bia a>"http://blog.linkuggbootsoutlet.com"> About lovembtshoes.com blog
180
[Mall3411] - $175.01 : </title>
html; charset=utf-8" />
keywords" content="Low Cost Custom-Made bretelles sexy mariage mariée robe de mariée Robes [Mall3411] Robes de Mariée Robes de mariée 2012 Robe de mariée sexy Robes de mariée robes Quinceanera Robes de bal Robes de soirée Robes de bal Robes de soirée Robes de cocktail " />
description" content=" Low Cost Custom-Made bretelles sexy mariage mariée robe de mariée Robes [Mall3411] - Nom de l'article: " />
- TOP_MENU_HOME
- Robes de cocktail
- Robes de soirée
- Robes de mariée
- Robes de bal
- Contactez-nous
- http:
//fr.weddingdressescompany.com/»,«http:/fr.weddingdressescompany.com/' ) " > Marque page