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Strings

Printing

Output a string to the console

Write the string "Hello World!" to STDOUT

haskell

main = putStrLn "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 "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?

haskell

import Network.CGI

query = "http://myserver.com/custinfo/edit.php?" ++ formEncode [("mode", "view"), ("fname", "Ron & Jan"), ("lname","Smith")]

string-wrap

Wrap the string "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.

haskell

wrap str
| length str <= 77 = [str]
| otherwise = [take 77 str] ++ wrap (drop 77 str)

mapM_ putStrLn . map ("> " ++) . wrap . concat . replicate 10 $ "The quick brown fox jumps over the lazy dog. "

Declaration

Define a string containing special characters

Define the literal string "\#{'}${"}/"

haskell

putStrLn "\"\\#{'}${\"}/\""

let special = "\\#{'}${\"}/"

Define a multiline string

Define the string:

"This

Is

A

Multiline

String"

haskell

s = "This \
\Is \
\A \
\Multiline \
\String"

Define a string containing variables and expressions

Given variables a=3 and b=4 output "3+4=7"

haskell

import Text.Printf

main = do
let a = 3
let b = 4
printf "%d+%d=%d" a b (a + b)

a = 3
b = 4
s = show a ++ "+" ++ show b ++ "=" ++ show (a + b)
main = putStrLn s

Manipulation

Reverse the characters in a string

Given the string "reverse me", produce the string "em esrever"

haskell

reverse "reverse me"

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"

haskell

unwords (reverse (words "This is the end, my only friend!"))

Text wrapping

Wrap the string "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.

haskell

import Data.List (intercalate)

-- our list of words ["The", "quick", "brown", ...]
dogs = concat$ replicate 10$ words "The quick brown fox jumps over the lazy dog."

-- ["The", "The quick", "The quick brown", ...]
concats = scanl1 (\s v -> s ++ " " ++ v)

-- takes list of words, returns list of lines
wordwrap :: Int -> [String] -> [String]
wordwrap maxwidth [] = []
wordwrap maxwidth ws = sentence : (wordwrap maxwidth restwords)
where
zipped = zip (concats ws) ws
(sentences, rest) = span (\(s,w) -> (length s) <= maxwidth) zipped
sentence = last (map fst sentences)
restwords = map snd rest

main = putStrLn ("> " ++ intercalate "\n> " (wordwrap 76 dogs))

Remove leading and trailing whitespace from a string

Given the string " hello " return the string "hello".

haskell

unwords (words " hello ")

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

haskell

Case

Make a string uppercase

Transform "Space Monkey" into "SPACE MONKEY"

haskell

toUpperCase oldstring converted = if oldstring == ""
then converted
else toUpperCase (tail(oldstring)) (converted ++ [Char.toUpper(head(oldstring))])

toUpperCase "Space Monkey" ""

toUpperCase = map Char.toUpper

toUpperCase "Space Monkey"

Make a string lowercase

Transform "Caps ARE overRated" into "caps are overrated"

haskell

import Char
str = map toLower "Caps ARE overRated"

Capitalise the first letter of each word

Transform "man OF stEEL" into "Man Of Steel"

haskell

import Data.Char

capitalizeWords = unwords . map capitalizeWord . words
where capitalizeWord [] = []
capitalizeWord (c:cs) = toUpper c : map toLower cs