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List:       haskell-cafe
Subject:    Re: [Haskell-cafe] foldlWhile
From:       "Serge D. Mechveliani" <mechvel () botik ! ru>
Date:       2004-11-22 6:41:47
Message-ID: 20041122094147.A345 () botik ! ru
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To my question of
  
>>  foldlWhile :: (a -> b -> a) -> (a -> Bool) -> a -> [b] -> a
>>  foldlWhile    f                p              a    bs  =
>>    case
>>        (bs, p a)
>>    of
>>    ([],    _    ) -> a
>>    (_,     False) -> a
>>    (b:bs', _    ) -> foldlWhile f p (f a b) bs'
>> 
>> foldl  does not seem to cover this.


Dylan Thurston wrote: On Nov 20, 2004 

> An alternative is
> 
>   foldlWhile f p a bs = last $ takeWhile p $ scanl f a bs
> 


Yes. Thank you. 
Inspecting Prelude, we find out that  scanl  expresses, mainly, 
the thing.

-----------------
Serge Mechveliani
mechvel@botik.ru




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