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

[Neil Mitchell]

Hi

> 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...

Thanks

Neil