[Haskell-beginners] Haskell code optimisation

[Abhishek Kumar]

Thanks Kim for your answer but as far as I understand strict evaluation
should save in space as expression is not expanded in terms of thunks,but I
can't understand time savings.Can you pls explain strict evaluation?

On Friday, December 11, 2015, Kim-Ee <ky3 at atamo.com> wrote:

> Have you tried BangPatterns? Compiled with optimization, I get 22 secs.
> Here's the full program:
>
> {-# LANGUAGE BangPatterns #-}
>
> f :: Int -> Int -> Int
> f !m !n
>    | m==0      = n+1
>    | n==0      = f (m-1) 1
>    | otherwise = f (m-1) (f m (n-1))
>
> main = putStrLn (show (f 4 1))
>
>
> -- Kim-Ee
>
> On Fri, Dec 11, 2015 at 9:47 PM, Abhishek Kumar <abhishekkmr18 at gmail.com
> <javascript:_e(%7B%7D,'cvml','abhishekkmr18 at gmail.com');>> wrote:
>
>> I was trying to write below program for ackerman function but it fails
>> (waits too long) for ack(4,1) whereas a recursive C program gives result in
>> 37secs.Can someone pls explain this behaviour and recomend some
>> optimisation.
>>
>> ------haskell code
>> f m n  | m==0 =n+1
>>            | n==0 = f  (m-1) 1
>>            | otherwise = f (m-1) (f m (n-1))
>>
>> Thanks
>> Abhishek Kumar
>>
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>>
>
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