[Haskell-beginners] question on typeclasses and applicatives

[Brandon S Allbery KF8NH]

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On 9/2/10 20:11 , Alec Benzer wrote:
> I guess I would then be concerned with why they didn't allow it in the
> standard (though I guess "well, it seemed to be a good idea at the
> time" answers that).

Keep in mind that type theory has advanced a *lot* since Haskell '98 was
frozen.  Quite a few things that are commonplace in modern GHC were
considered prohibitively difficult or expensive to implement back then;
others were adjudged "too confusing" (which got monad comprehensions removed
and the monomorphism restriction added; the latter is almost universally
considered a mistake).

> I think I also would want to avoid doing things not in the language
> standard on principle, since my instinct would tell me that if only a
> particular compiler implements, I shouldn't use it because it'll
> produce non-standard code. Though this sort of comes comes from C/C++
> where there are different compilers on different platforms, but I
> guess with haskell people pretty much use ghc everywhere?

More to the point, ghc is the language developers' playground, so other
compilers (the few that there are) generally follow ghc's lead.

- -- 
brandon s. allbery     [linux,solaris,freebsd,perl]      allbery at kf8nh.com
system administrator  [openafs,heimdal,too many hats]  allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university      KF8NH
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