[plt-scheme] Reexpansion of modules

1. I considered the idea of developing larceny modules inside of DrS  
back in 2002. Then I learned more about Larceny and how small it is.  
And we didn't have Eli's FFI yet for integrating Lareceny-compiled  
modules back into PLT Scheme. Now this idea is worth studying because  
you don't want to use Larceny for anything else than ASM. But perhaps  
at that level it has value! (I'll talk to Eli next week on this.)

2. Yes, we could expand PLT Scheme to PLT Scheme [core] first but  
even in this core language you have so many library calls and  
extensions, resolution of semantic issues, etc, that NOW WATCH

  -- compiling the rest in Larceny is either impossible or
  -- it doesn't produce code that is faster than PLT Scheme and  
faithful to its semantics.
     [Evaluation order is just one "switch" (ever wondered about the  
love and attachment of compiler hacks to switches?)
     that slows down object code in Larceny a lot. Why? I don't know.]

-- Matthias




On Aug 19, 2006, at 1:29 PM, Jens Axel Søgaard wrote:

> Reexpansion of modules
> ======================
>
> The recent thread on MzScheme and Larceny were thought provoking.
> Even though Matthias has lost hope to see a bridge between MzScheme
> and Larceny, maybe it is possible cross the gap using a tightrope?
> Intended not for the masses, but for the adventurous.
>
> Making a subset of MzScheme compilable via Larceny would still
> be an improvement over the present situation, where one needs
> to dust of the C compiler, when extra speed is needed.
>
> The ideal situation would be a solution that made it possible to
> develop code using DrScheme and the standard set of tools. One way
> would be to make a module based language "larceny", such that
>
>   (module A larceny
>     <...>)
>
> would run directly in DrScheme, and at the press of a button,
> one could generate corresponding Larceny code.
>
> A small core language combined with the full module and macro
> system of MzScheme would be enough for most speed challenged
> programs. These pieces could then be reintroduced to MzScheme
> through Eli's FFI.
>
>
> Ray Racine writes:
>
> > Just the other day I was wondering what it would take to write an
> > MzScheme to Scheme compiler (or translator). :)
> >
> > What I mean is hooking into the MzScheme interpreter and/or mzc to
> > emit basic Scheme as an IL.  Said IL scheme is then compiled by
> > Larceny.
> > (Fully expand all syntax, unroll modules by prefixing all symbols,
> > emit scheme.)
>
> This reminded me of some old code I wrote, which used that idea.
> Instead of reimplementing the MzScheme macro expander (a daunting task
> for non-Flatts) it piggybacks on the MzScheme expander.
>
> It were old enough to expect paths represented as strings (and
> pre-unicode too?). Nevertheless it seems to work at least on simple
> examples. Maybe the following description will tell whether the idea
> is sound?
>
> The idea is first to use MzScheme's EXPAND to expand all modules. This
> brings the code in a known form (NB: the code were written before
> require-template). Then all modules are "reexpanded" - all identifiers
> are renamed to include module name, phase and their original name. If
> a module is instantiated in multiple phases the code will thus appear
> multiple times in the resulting code.
>
> Is the idea sound?
>
> Would it be worthwhile to revive this code - or is there a
> better approach?
>
>
> Example 1
> ---------
>
> ; a.scm
> (module a mzscheme
>   (provide x inc-x! mx)
>   (define x 0)
>   (define-syntax mx (lambda (stx) #'x))
>   (define (inc-x!) (set! x (+ x 1))))
>
> Reexpanding "a.scm" results in:
>
> (begin
>   '(module a mzscheme)
>   '(require-for-syntax mzscheme)
>   '(provide x inc-x! mx)
>   (define-values (a:0:x) 0)
>   (define-syntaxes (a:0:mx) (lambda (stx) (quote-syntax a:0:x)))
>   (define-values (a:0:inc-x!) (lambda () (set! a:0:x (+ a:0:x 1)))))
>
>
> Example 2
> ---------
>
> ; a.scm as before
>
> ; b.scm
> (module b mzscheme
>   (require "a.scm")
>   (inc-x!)
>   (display (mx)) (newline))
>
> Reexpanding "b.scm" results in:
>
> (begin
>   '(module a mzscheme)
>   '(require-for-syntax mzscheme)
>   '(provide x inc-x! mx)
>   (define-values (a:0:x) 0)
>   (define-syntaxes (a:0:mx) (lambda (stx) (quote-syntax a:0:x)))
>   (define-values (a:0:inc-x!) (lambda () (set! a:0:x (+ a:0:x 1)))))
>
> (begin
>   '(module b mzscheme)
>   '(require-for-syntax mzscheme)
>   '(require "a.scm")
>   (a:0:inc-x!)
>   (display a:0:x)
>   (newline))
>
> Example 3
> ---------
> ; a.scm as before
> ; b.scm as before
>
> ; c.scm
> (module c mzscheme
>   (provide mx2)
>   (require "b.scm")
>   (require "a.scm")
>   (require-for-syntax "a.scm")
>   (define-syntax mx2 (lambda (stx) (datum->syntax-object stx (mx))))
>   (display "phase 1: ") (display (mx2)) (newline)
>   (display "phase 0: ") (display (mx))  (newline)
>
>   (+)
>   (- 1))
>
> Reexpanding "c.scm" results in:
>
> (begin
>   '(module a mzscheme)
>   '(require-for-syntax mzscheme)
>   '(provide x inc-x! mx)
>   (define-values (a:1:x) 0)
>   (define-syntaxes (a:1:mx) (lambda (stx) (quote-syntax a:1:x)))
>   (define-values (a:1:inc-x!) (lambda () (set! a:1:x (+ a:1:x 1)))))
>
> (begin
>   '(module a mzscheme)
>   '(require-for-syntax mzscheme)
>   '(provide x inc-x! mx)
>   (define-values (a:0:x) 0)
>   (define-syntaxes (a:0:mx) (lambda (stx) (quote-syntax a:0:x)))
>   (define-values (a:0:inc-x!) (lambda () (set! a:0:x (+ a:0:x 1)))))
>
> (begin
>   '(module b mzscheme)
>   '(require-for-syntax mzscheme)
>   '(require "a.scm")
>   (a:0:inc-x!)
>   (display a:0:x)
>   (newline))
>
> (begin
>   '(module c mzscheme)
>   '(require-for-syntax mzscheme)
>   '(provide mx2)
>   '(require "b.scm")
>   '(require "a.scm")
>   '(require-for-syntax "a.scm")
>   (define-syntaxes (c:0:mx2) (lambda (stx) (datum->syntax-object  
> stx a:1:x)))
>   (display "phase 1: ")
>   (display 0)
>   (newline)
>   (display "phase 0: ")
>   (display a:0:x)
>   (newline)
>   (+)
>   (- 1))
>
>
> The code is attached in a zip-file. My mail server rejected plain
> Scheme files.
>
> -- 
> Jens Axel Søgaard
> Planet Scheme      -  <http://www.scheme.dk/planet/>
> Everything Scheme  -  <http://www.scheme.dk/blog/>
>
>
> <reexpand.zip>
> _________________________________________________
>   For list-related administrative tasks:
>   http://list.cs.brown.edu/mailman/listinfo/plt-scheme