[gambit-list] Thoughts on Scheme

Mikael mikael.rcv at gmail.com
Mon Jan 7 12:17:29 EST 2013


Hi Jason,

(Just so I got you right, by generality of built-in procedures you do
actually mean generics, as in, different actual routines are invoked based
on type?)

I believe something like a generics - multiple dispatch system would be
really handy.

Through algorithms for analysis through abstract interpretation like 2-CFA,
you can probably pin down quite a lot of data types - maybe even 95% for
typical-ish code - and thus what exact procedures to use at expansion time
and thus also get a really good performance.

Prof. Matt Might at Utah works with abstract interpretation, perhaps he
published an implementation of a Scheme-based abstract interpreter of
Scheme.

I suppose implementing this atop standard Scheme makes good sense.

2013/1/7 Jason Felice <jason.m.felice at gmail.com>

> Thanks for the feedback.  I appreciate it.  I think I'd like to narrow my
> focus to the primary thing, which was the lack of generality of the
> built-in procedures, and generics.
>
> Making these efficient to compile (especially with a module system) seems
> hard, but rewarding.  I'm thinking about how to do this more.  Personally,
> I don't think efficiency in terms of constant factors should often win
> versus code which could be more general.
>


> Clearly this is a value choice; however, I wonder how well a compiler can
> eliminate type dispatching without adding type annotation to the language.
>

Without having studied it too deep, I believe abstract interpretation can
help you a lot with this. If you rely on that objects have a type slot to
them, like Gambit's define-type:s have (it's ##vector-ref :able on slot 0
or 1), then you can always dig this out during runtime and handle it the
correctly then.


> So, I'm thinking about these things and will let them stew for... another
> 10 years?  I don't know.
>
> Thanks,
> -Jason
>

Please feel free to share reflections you're coming up with along the way.

Brgds,
Mikael
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