Difference between revisions of "Talk:Higher order function"

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(New page: 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] -...)
 
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I need a resourse of haskell from scratch and also need someone to explain in details the quicksort that is published:
  
I need a resourse of haskell from scratch and also need someone to explain in details the quicksort that is published:
   
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⚫
quicksort :: Ord a => [a] -> [a]
  
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⚫
quicksort [] = []
  
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----
⚫
quicksort (p:xs) = (quicksort lesser) ++ [p] ++ (quicksort greater)
  
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where
  
  ⚫
quicksort :: Ord a => [a] -> [a]
⚫
lesser = filter (< p) xs
  
  ⚫
quicksort [] = []
⚫
greater = filter (>= p) xs
  
  ⚫
quicksort (p:xs) = (quicksort lesser) ++ [p] ++ (quicksort greater)
  ⚫
where
  ⚫
lesser = filter (< p) xs
  ⚫
greater = filter (>= p) xs
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----
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without line no 1, it works fine
  
without line no 1, it works fine
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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.

xs ++ ys concatenates the lists xs and ys

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)

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