On Thu, Mar 06, 2008 at 11:43:08AM +0000, Simon Peyton-Jones wrote:
> See 4.5.5 in the Report http://haskell.org/onlinereport/decls.html.
>
> Rule 1 says that 'compress' is not generalised. So it gets the type
> [t] -> [t]
> where 'a' is an as-yet-un-determined type; in implementation terms, a
> unification variable.
>
> Rule 2 says "Any monomorphic type variables that remain when type inference
> for an entire module is complete, are considered ambiguous, and are resolved
> to particular types using the defaulting rules". But in this case no
> monomoprhic variables remain, because by then the type of compress has been
> refined to [Char] -> [Char]
Ah! it all makes sense now. excellent. It has been a persistent
annoyance that jhc gets dinged by the monomorphism restriction more than
ghc, but now I see why. thanks!
John
--
John Meacham - ⑆repetae.net⑆john⑈
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