[Haskell-cafe] Re: Why purely in haskell?

[Daniel Yokomizo]

On Jan 10, 2008 3:36 PM, Achim Schneider <barsoap at web.de> wrote:
> jerzy.karczmarczuk at info.unicaen.fr wrote:
>
> > Niko Korhonen writes:
> >
> > ...
> > > Although it could be argued that laziness is the cause of some very
> > > obscure bugs... <g>
> > > Niko
> >
> > Example, PLEASE.
> >
> [1..] == [1..]
>
> , for assumed operational semantics of ones own axiomatic semantics.
> Bugs are only a misunderstanding away.

It has nothing to do with laziness, but with using an algebraic
function (==) with a codata structure (stream). If Haskell kept
laziness but enforced separation of data and codata such code wouldn't
compile. Lazy lists or streams never are a problem, but you can't
(generically) fold codata.

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Best regards,
Daniel Yokomizo