[m-users.] Issue with assoc_list and other container types

[Peter Wang]

On Fri, 21 Jan 2022 20:17:36 +0100 Volker Wysk <post at volker-wysk.de> wrote:
> > 
> > This works for assoc_list because the type definition is exported from
> > the module. It won't work for types like types like map where the type
> > is deliberately kept private.
> 
> I see. But it would work for assoc_list. Perhaps change the modes of the
> predicates and functions in question?

If I'm remembering correctly, historically there were concerns about the
performance impact on the compiler if inst parameters or complex insts
were more widely used. There may have been some concerns about
correctness as well, I guess. (My view may be coloured by having to fix
some bugs with constrained polymorphic modes a few years ago.)

Obviously any problems uncovered would (necessarily) be addressed if we
started using parameteric modes in the standard library, so it may just
be a matter of committing to it.

Peter