[m-dev.] Re: Visual vs total arity clash example [fwd]

[Fergus Henderson]

On 27-Jan-2000, Ralph Becket <rbeck at microsoft.com> wrote:
> > Fact: to allow for *OLD* code using DCGs or code written 
> > explicitly using
> > io__state, to still work with the new io.m predicates that 
> > use EDCGs I must
> > allow EDCG predicates to be called in expanded form.
> 
> Can someone remind me again why EDCGs are not just a simple
> source transformation and hence why there should be any problem
> with integrating EDCG code with plain code?

The main reasons are these:

  - We want to support higher-order EDCG code.
    If you want higher-order calls to look like ordinary
    first-order EDCG code, then this requires keeping
    track of hidden arguments in the type system.

  - We want to support inference of the `pred' declaration
    for EDCG clauses.

> Question: above I used a polymorphic htype - I presume that's
> all right?

Not in the current implementation, but yes we do plan
to support it eventually.

-- 
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 128.250.37.3        |     -- the last words of T. S. Garp.
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