[gambit-list] Profiling of expanded code?

Abdulaziz Ghuloum aghuloum at cs.indiana.edu
Sat Nov 15 13:19:44 EST 2008

On Nov 15, 2008, at 12:38 PM, William Cook wrote:

> Why doesn't the Gambit define-macro (and syntax-case) just
> do the right thing?

The R6RS syntax-case system that was developed for Ikarus
(ported to some 12 other Scheme implementations including
Gambit) does precisely that.  At every macro transcription
step, the source of the macro input (the form itself) is
applied to the list of annotations of the output form, and
duplicates are cancelled (in the same manner how marks
cancel, but that's irrelevant).  This gives allows syntax
errors to show the macro expansion steps that resulted in
the syntax error (when available); instead of just showing
the final error.

Here's an example:

$ cat q.ss
(import (rnrs))

(define-syntax let^
   (syntax-rules ()
     [(_ ([x* v*] ...) e e* ...)
      ((lambda (x* ...) e e* ...) v* ...)]))

(define-syntax L
   (syntax-rules ()
     [(_ x v e) (let^ ([x v]) e)]))

(L v 13 (L 12 x (+ v x)))

$ ikarus --r6rs-script q.ss
Unhandled exception:
  Condition components:
    1. &who: lambda
    2. &message: "not an identifier"
    3. &syntax:
        form: (lambda (12) (+ v x))
        subform: 12
    4. &trace: #<syntax (lambda (12) (+ v x))>
    5. &trace: #<syntax (let^ ((12 x)) (+ v x))>
    6. &trace: #<syntax (L 12 x (+ v x)) [char 214 of q.ss]>


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