[m-dev.] diff: fix bug with simplify.m & existential types
fjh at cs.mu.OZ.AU
Wed Aug 5 17:42:23 AEST 1998
On 05-Aug-1998, David Glen JEFFERY <dgj at cs.mu.OZ.AU> wrote:
> > % The predicate has_type/2 is basically an existentially typed
> > % inverse to the function type_of/1. It constrains the type
> > % of the first argument to be the type represented by the
> > % second argument.
> > %
> > % Warning: support for existential types is still experimental.
> > %
> > :- some [T] pred has_type(T::unused, type_info::in) is det.
> Yuck! Should that actually be legal?
Sure, it's not only legal, it's actually quite useful -- see the changes
to the standard library that I posted recently. Without that sort of
thing, the only way of doing certain things involves using unsafe type
casts and the like.
Fergus Henderson <fjh at cs.mu.oz.au> | "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh> | of excellence is a lethal habit"
PGP: finger fjh at 22.214.171.124 | -- the last words of T. S. Garp.
More information about the developers