# Haskell a la carte

### From HaskellWiki

## Contents |

## 1 Apéritifs

Foretaste of an excellent meal.

qsort :: Ord a => [a] -> [a] qsort [] = [] qsort (x:xs) = qsort (filter (<x) xs) ++ [x] ++ qsort (filter (>x) xs))

- Quicksort in three lines (!). Sorts not only integers but anything that can be compared.

fibs = 1:1:zipWith (+) fibs (tail fibs)

- The
*infinite*list of fibonacci numbers. Just don't try to print all of it.

- The

linecount = interact $ show . length . lines wordcount = interact $ show . length . words

- Count the number of lines or words from standard input.

## 2 Entrées

How to eat?

square x = x*x

- The function which maps a number to its square. While we commonly write parenthesis around function arguments in mathematics and most programming languages, a simple space is enough in Haskell. We're going supply arguments all around, so why clutter the notation with unnecessary ballast?