# 99 questions/Solutions/4

### From HaskellWiki

< 99 questions | Solutions(Difference between revisions)

Line 16: | Line 16: | ||

<haskell> | <haskell> | ||

myLength' xs = snd $ last $ zip xs [1..] -- Just for fun | myLength' xs = snd $ last $ zip xs [1..] -- Just for fun | ||

+ | </haskell> | ||

+ | |||

+ | <haskell> | ||

+ | myLength = sum . map (\x -> 1) | ||

</haskell> | </haskell> | ||

This is <hask>length</hask> in <hask>Prelude</hask>. | This is <hask>length</hask> in <hask>Prelude</hask>. |

## Revision as of 15:02, 25 October 2011

(*) Find the number of elements of a list.

myLength :: [a] -> Int myLength [] = 0 myLength (_:xs) = 1 + myLength xs

myLength' = foldl (\n _ -> n + 1) 0 myLength'' = foldr (\_ n -> n + 1) 0 myLength''' = foldr (\_ -> (+1)) 0 myLength'''' = foldr ((+) . (const 1)) 0

myLength' xs = snd $ last $ zip xs [1..] -- Just for fun

myLength = sum . map (\x -> 1)

length

Prelude