[Haskell-cafe] Maintaining laziness

Miguel Mitrofanov miguelimo38 at yandex.ru
Mon Dec 29 15:59:46 EST 2008

Seems useful.

BTW, why on earth should "inits undefined" be "undefined" instead of  
"[]:undefined"? I mean, come on, we all know that "inits anything"  
starts with []!

On 29 Dec 2008, at 20:41, Henning Thielemann wrote:

> In case someone cares - after some battles with functions that are  
> less lazy than expected, I have written a tutorial on how to get  
> functions lazy and how to test, whether they are actually lazy:
> http://www.haskell.org/haskellwiki/Maintaining_laziness
> I found it especially enlightening, that one can avoid a 'force'  
> function in a lazy parser by making the possibility of a parser  
> failure explicit in its type. I.e. a parser that cannot fail, need  
> no 'force'. (I learnt that in polyparse the 'force' function is  
> hidden in 'apply':
>  http://hackage.haskell.org/packages/archive/polyparse/1.1/doc/html/Text-ParserCombinators-PolyLazy.html#v%3Aapply 
>   )
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