ImplicitParams and MonoLocalBinds
Iavor Diatchki
iavor.diatchki at gmail.com
Fri Mar 29 00:39:33 CET 2013
Hi,
This does not appear to be related to ImplicitParameters, rather
`MonoLocalBinds` is not working as expected.
Here is an example without implicit parameters that compiles just fine, but
would be rejected if `p` was monomorphic:
{-# LANGUAGE NoMonomorphismRestriction, MonoLocalBinds #-}
class C a where
f :: a -> ()
instance C Bool where f = const ()
instance C Char where f = const ()
g = let p = f
in (p 'a', p True)
-Iavor
On Fri, Mar 22, 2013 at 1:39 AM, Roman Cheplyaka <roma at ro-che.info> wrote:
> The value of the following expression
>
> let ?y = 2 in
> let p = ?y in
> let ?y = 1 in
> p
>
> depends on whether the second binding is generalised.
>
> MonomorphismRestriction makes it not generalise, hence the value is 2.
>
> What surprises me is that MonoLocalBinds doesn't have this effect.
>
> Prelude> :set -XImplicitParams -XNoMonomorphismRestriction
> -XMonoLocalBinds
> Prelude> let ?y = 2 in let p = ?y in let ?y = 1 in p
> 1
>
> What's going on here?
>
> Roman
>
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