[Haskell-cafe] A Mascot

[MigMit]

You're probably missing the fact that it's much harder to understand how the Haskell program works without (_|_). I've seen lots of questions like "why doesn't my recursion work" that could be answered simply as "because your function is strict, so (_|_) is it's minimal fixpoint".

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Nov 16, 2011, в 15:31, Jesse Schalken <jesseschalken at gmail.com> написал(а):

> I like the idea of a mascot. I like the idea of a lamb called Da, as most of Haskell's strength comes from it's closeness to pure lambda calculus.
> 
> A few things I'd like to see in a mascot:
> - Simple. You should be able to draw it in a few seconds.
> - Look good in black and white.
> - Have obvious features so it is identifiable from a distance.
> - Be a little bit cute.
> 
> I don't see why ⊥ has to be featured. ⊥ means a computation can terminate without returning a value. That is a flaw, not a strength. If a computation may fail, return a Maybe or Either String. If a computation might not terminate, let it not terminate and I can find out why with my debugger. That covers all the use cases of ⊥. It also undermines the type system as beginners often write functions which return ⊥ where they should either be returning a Maybe or Either String, or expressing the violated precondition in the type system so it can be tested at compile time. What am I missing?
> 
> On Wed, Nov 16, 2011 at 9:47 PM, Bas van Dijk <v.dijk.bas at gmail.com> wrote:
> On 16 November 2011 11:05, MigMit <miguelimo38 at yandex.ru> wrote:
> > Maybe it's just me, but I've thought that being non-strict just means that it's possible for a function to produce some value even if it's argument doesn't; in other words, that it's possible to have "f (_|_) ≠ (_|_)". If there was no such thing as (_|_), what would non-strictness mean?
> 
> Thanks, non-strictness is indeed defined using ⊥ like you mentioned.
> 
> I think I was confusing non-strict evaluation with coinduction. They
> have the same advantages but the latter is less powerful but safer
> than the former.
> 
> Bas
> 
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