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Structure
Conditionals

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.
scala
val name = "Bob"
if (name.equals("Bob")) printf("Hello, %s!\n", name)
val name = "Bob"

// Scala supports operator overloading, so the following works correctly
if (name == "Bob") printf("Hello, %s!\n", name)
csharp
if (name == "Bob") Console.WriteLine("Hello, {0}!", name);
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"
scala
val age = 42
if (age > 42) println("You are old") else println("You are young")
println( "You are " + ( if ( age > 42 ) "old" else "young" ) )
csharp
int age = 41;

if (age > 42)

System.Console.WriteLine("You are old");
else
System.Console.WriteLine("You are young");


cpp
if (age > 42) Console::WriteLine("You are old");
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)

scala
val age = 65

if (age > 84) println("You are really ancient")
else if (age > 30) println("You are middle-aged")
else println("You are young")
csharp
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");
Console.WriteLine("You are {0}", ((age > 84) ? "really ancient" : (age > 30) ? "middle-aged" : "young"));
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");
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
scala
object FourToTwenties {
def unapply (n: Int) = (4 to 20).contains(n % 100)
}

def suffix (n: Int) = {
n match {
case FourToTwenties() => "th"
case n if n % 10 == 1 => "st"
case n if n % 10 == 2 => "nd"
case n if n % 10 == 3 => "rd"
case _ => "th"
}
}

for (n <- 1 to 40) {
println(n.toString + suffix(n))
}

csharp
public static string GetOrdinal(int i)
{
if (i > 10 && i < 20) return i.ToString() + "th";
switch (i % 10)
{
case 1:
return i.ToString() + "st";
case 2:
return i.ToString() + "nd";
case 3:
return i.ToString() + "rd";
default:
return i.ToString() + "th";
}
}
public static string GetOrdinal(int i)
{
if (i > 10 && i < 20) return i.ToString() + "th";
switch (i % 10)
{
case 1:
return i.ToString() + "st";
break;
case 2:
return i.ToString() + "nd";
break;
case 3:
return i.ToString() + "rd";
break;
default:
return i.ToString() + "th";
break;
}
}
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();
}
Loops

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.
scala
var x = 1 ; while (x < 150) { printf("%d,", x) ; x *= 2 }
csharp
int x = 1;

while (x < 150)
{
x *= 2;
Console.Write("{0},", x);
}
cpp
int x = 1;

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;

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"
scala
val dice = new GenRandInt(1, 6) ; var rnd = 0 ; var fmt = ""
do { rnd = dice.next ; fmt = if (rnd != 6) "%d," else "%d" ; printf(fmt, rnd) } while (rnd != 6)
csharp
System.Random die = new System.Random();
int roll;

do
{
roll = die.Next(1, 6);
Console.Write(roll);
if (roll < 6) Console.Write(",");
}
while (roll != 6);
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();

Perform an action a fixed number of times (FOR)

Display the string "Hello" five times like "HelloHelloHelloHelloHello"
scala
// Using overloaded '*' operator (String-specific)
print("Hello" * 5)
List.range(0, 5) foreach { (_) => print("Hello") }
for (_ <- List.range(0, 5)) print("Hello")
// Lazy version
for (_ <- Stream.range(0, 5)) print("Hello")
dotimes(5, _ => print("Hello"))
(0 until 5) foreach { (_) => print("Hello") }
5 times { print("Hello") }
csharp
string text = "Hello";

for (int i = 0; i < 5; i++)
{
Console.Write(text);
}
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!"
scala
for (i <- List.range(1, 11).reverse) printf("%d .. ", i) ; println("Liftoff!")
for (i <- List.range(-10, 0)) printf("%d .. ", (-i)) ; println("Liftoff!")
var i = 10 ; while (i > 0) { printf("%d .. ", i) ; i -= 1 } ; println("Liftoff!")
for (i <- -10 to -1) printf("%d .. ", (-i)) ; println("Liftoff!")
csharp
for (int i = 10; i > 0; i--)
{
Console.Write("{0} .. ", i);
}

Console.WriteLine("Liftoff!");
cpp
for(int i = 10; i != 0; --i) Console::Write("{0} .. ", i);
Console::WriteLine("Liftoff!");