# Talk:Higher order function

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Yasmin.Fathy (Talk | contribs) |
(Added an answer) |
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− | quicksort :: Ord a => [a] -> [a] |
+ | quicksort :: Ord a => [a] -> [a] |

− | quicksort [] = [] |
+ | quicksort [] = [] |

− | quicksort (p:xs) = (quicksort lesser) ++ [p] ++ (quicksort greater) |
+ | quicksort (p:xs) = (quicksort lesser) ++ [p] ++ (quicksort greater) |

− | where |
+ | where |

− | lesser = filter (< p) xs |
+ | lesser = filter (< p) xs |

− | greater = filter (>= p) xs |
+ | greater = filter (>= p) xs |

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Thanks in advance |
Thanks in advance |
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+ | ---- |
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+ | You can better ask this sort of questions via the [http://haskell.org/mailman/listinfo/beginners Haskell-beginners mailinglist] or [http://stackoverflow.com/ StackOverflow]; the talk pages are usually used for discussion of a wikipage. |
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+ | There are tutorials listed at http://www.haskell.org/haskellwiki/Tutorials |
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+ | Line no. 1 is correct, it describes the type of the function. |
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+ | <hask>xs ++ ys</hask> concatenates the lists <hask>xs</hask> and <hask>ys</hask> |
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+ | You can find a description of how this function works at http://learnyouahaskell.com/recursion ; the function at this pages looks different, but is actually the same. |
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+ | [[User:Henk-Jan van Tuyl|Henk-Jan van Tuyl]] 10:24, 10 November 2011 (UTC) |

## Latest revision as of 10:24, 10 November 2011

I'm a beginner in Haskell and needs help I need a resourse of haskell from scratch and also need someone to explain in details the quicksort that is published:

quicksort :: Ord a => [a] -> [a] quicksort [] = [] quicksort (p:xs) = (quicksort lesser) ++ [p] ++ (quicksort greater) where lesser = filter (< p) xs greater = filter (>= p) xs

without line no 1, it works fine
what about line three ? and how we use ++ as concatenate ???

Thanks in advance

You can better ask this sort of questions via the Haskell-beginners mailinglist or StackOverflow; the talk pages are usually used for discussion of a wikipage.

There are tutorials listed at http://www.haskell.org/haskellwiki/Tutorials

Line no. 1 is correct, it describes the type of the function.

You can find a description of how this function works at http://learnyouahaskell.com/recursion ; the function at this pages looks different, but is actually the same.

Henk-Jan van Tuyl 10:24, 10 November 2011 (UTC)