Help with cast error

[Conal Elliott]

Thanks for the summary and paper pointer! I'll study up.  -- Conal


On Thu, Apr 24, 2014 at 12:58 AM, Simon Peyton Jones
<simonpj at microsoft.com>wrote:

>  (a ~ b)  is a *boxed*, *nominal* equality.
>
> (a ~R# b)  is an *unboxed, representational* equality
>
>
>
> So it is rightly rejected.
>
>
> For the boxed/unboxed thing, the paper “practical aspects…” gives more
> detail.
> http://research.microsoft.com/en-us/um/people/simonpj/papers/ext-f/
>
>
>
> I think you already know about the nominal/representational distinction.
>
>
>
> Simon
>
>
>
> *From:* Glasgow-haskell-users [mailto:
> glasgow-haskell-users-bounces at haskell.org] *On Behalf Of *Conal Elliott
> *Sent:* 24 April 2014 01:29
> *To:* glasgow-haskell-users at haskell.org; ghc-devs at haskell.org; Richard
> Eisenberg; Simon Peyton Jones
> *Subject:* Help with cast error
>
>
>
> I'd appreciate help with a cast-related Core Lint error I'm getting with a
> GHC plugin I'm working on:
>
>     Argument value doesn't match argument type:
>     Fun type:
>         Enc (Vec ('S 'Z) Bool) ~ (Bool, ()) =>
>         EP (Enc (Vec ('S 'Z) Bool)) -> EP (Bool, ())
>     Arg type:
>         ~R# (Enc (Vec ('S 'Z) Bool)) (Bool, ())
>     Arg:
>         CO Sub (TFCo:R:EncVec[0] <'Z>_N <Bool>_N)
>            ; (Sub TFCo:R:EncBool[0], Sub (TFCo:R:EncVec0[0] <Bool>_N))_R
>
> (I omitted the module prefixes for brevity.) Do I have a role wrong here,
> or maybe something more fundamental?
>
> I can easily supply more info if it'd help.
>
> Thanks, -- Conal
>
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