# Difference between revisions of "99 questions/Solutions/4"

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< 99 questions | Solutions

(correction (foldl) and shortened version of foldr) |
Citizen428 (talk | contribs) m |
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myLength'' = foldr (\_ n -> n + 1) 0 |
myLength'' = foldr (\_ n -> n + 1) 0 |
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myLength''' = foldr (\_ -> (+1)) 0 |
myLength''' = foldr (\_ -> (+1)) 0 |
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+ | </haskell> |
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+ | |||

+ | <haskell> |
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+ | myLength' xs = snd $ last $ zip xs [1..] -- Just for fun |
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</haskell> |
</haskell> |
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## Revision as of 22:46, 1 December 2010

(*) 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' xs = snd $ last $ zip xs [1..] -- Just for fun
```

This is `length`

in `Prelude`

.