Re: [stack] Cat 0.14 Release

Christopher Diggins <[email protected]> wrote:
> William Tanksley, Jr <[email protected]> wrote:
> > Impressive.

> Thank you. :-)

Talk is cheap -- code (and good specifications) are much harder.

> > Can macros be typechecked?

> How were you thinking? I plan to add the feature later on that value
> variables can have type restrictions, like:
> macro { $a:int $a:int add } => { $a $a add_int }

That's essentially what I was thinking, yes. I guess I should call
those type guards rather than type checks, since they can't make the
macro valid or invalid; rather, they force the macro to only apply to
text if the types involved match.

> For now there isn't such features.

That's just fine.

> > Are macros specifically checked for
> > identity, is it assumed, or can macros cause wildly different results?

> The macros are assumed to be compatible with the langauge semantics.

Assumptions are just fine, also.

> If MetaCat matures later on then it could be concievable that MetaCat
> actually defines the operational semantics of the language, which
> would be trluy mind-blowing, but not outsiode of the realm of
> possibility. Alan Kay I believe is working on something similar.

A very interesting point! Actually, this did pop into my mind, since
your macro notation reminded me of Kerby's combinator notation.

> > Can a macro cause type-conformant code to be non-conformant?

> Yep.

Is code typechecked both before and after substitution?

> > I see that it's implementation-dependant whether a macro is allowed to
> > reduce code. I think that makes sense, but I think that should
> > probably be formalized a bit,

> I agree.

...but saying "should probably be formalized" is a long way from doing
the work to formalize them. :-)

> > and control over whether a macro reduces
> > code that it matches be given over to the programmer (possibly with a
> > simple rule to prevent huge delays). But that's a HUGE project,
> > obviously.

> It might not be too bad, if I add namespaces, macro prioritization,
> and macro expansion directives. I can imagine a simple import
> directive inside of a namespace, that brings macro rules in to bear on
> a specific scope (e.g. curly brace blocks), and other directives that
> allow control.

True. I was thinking of a system which could express arbitrary
identity transformations, and coordinate among them so that the
language's entire optimizer could be expressed in its metalanguage.
THAT is a big challenge.

> The big challenge is to do such things elegantly.

Yes, elegance is difficult.

> The notion of
> namespaces is something that I have been playing with for a while and
> have somewhat prepared in the code-base.

Cool.

> Thanks for the feeback.

Thank you for the solid work!

> Christopher

-Billy