Re: [MLton] substring an eq type?

[Matthew F. <mat...@gm...>]

On Thu, Nov 21, 2013 at 7:09 PM, Henry Cejtin
<hen...@sb...> wrote:
> Reading your mail I checked, and I see that MLton believes that ''a
> VectorSlice.slice
> is also an eq type (when ''a is).  That doesn't seem to be what the
> basis library says,
> nor is it what SML/NJ does.  I.e., neither the polymorphic nor the monomorphic
> vector slices should be eq types but both are.
>
> For the polymorphic versions, the fact that the basis library book
> says (on pages 122
> and 405) says
>       structure ArraySlice:> ARRAY_SLICE
>       structure VectorSlice:> VECTOR_SLICE
> and that the interface is
>        type 'a slice
> for each of them, that seems to be explicitly disallowed.
>
> Unfortunately, that logic would also apply to all of the monomorphic
> vectors (except
> for CharVector and WideCharVector) since page 211 just says that MONO_VECTOR
> specifies `type vector' and only those two have where type vector = and eq type.
>
> I must be missing something here.

I don't think that you are missing anything.  MLton is exposing more
equality status than it should.  I tried throwing a few ":>" opaque
signature matchings for some of the slice functors, but there were a
lot of type errors.  Will probably take a bit more tweaking to hide
the equality status all the way through.