Re: [Sml-implementers] extensions to SML

[Dave B. <da...@ta...>]

At 14:20 17/09/2001, Matthias Blume wrote:
>I agree with Bob and others who would rather drop polymorphic equality.  

One possibility would be to keep the notion of equality type, and to
replace the polymorphic equality operation with a function overloaded on
equality types.  This would remove the notion of "equality type variable",
and make the language more uniform.

Daniel suggested the opposite approach: keeping polymorphic equality but
getting rid of eqtypes (as in OCaml).  I don't like this at all -- I think
it's one of the weak points of OCaml.  As far as I'm aware, if I define a
set type using unsorted lists in OCaml, the equality operator compares the
representation of two values.  In SML I can use abstraction to make the
type non-eqtype, which seems much preferable.  OCaml's equality can even
return different results when comparing floating point numbers (when NaN),
depending on whether the compiler can deduce the types involved!

To be honest, I doubt that changing the current definition is worthwhile,
compared to other improvements we could be doing.

Dave.