a faster, accumulating mapM (was Re: [Haskell-cafe] mapM vs mapM_ performance)

Neil Mitchell ndmitchell at gmail.com
Sat Apr 26 05:44:48 EDT 2008


> I didn't say I agree, I most certainly don't. What I meant with my
>  comment was that a slowdown of 10x, just to preserve laziness, is
>  perfect fuel for those who claim that laziness is good in theory but
>  bad in practice.

A bad implementation of laziness will always be slower than a bad
implementation of strictness - as we have strict CPU's. However,
laziness gives you some really cool opportunities for deforestation
and supercompilation - so at some point Haskell will overcome the
performance penalty of laziness and start to reap the performance
benefits - I think...



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