[plt-scheme] Pattern-matching macro chokes on conditional statement which would otherwise work.

Wait. It seems that you're right.
I'm running version 371. So I'll update now.

:) Thanks. I'll update you in how things go.

On Jan 19, 2008 3:57 PM, Gregory Cooper <greg at cs.brown.edu> wrote:

> What version of DrScheme are you running?  There was a bug in the v371
> debugger that would produce error messages like that, but it should
> have been fixed in v372 (and in svn as of r7169 I think).
>
> On Jan 19, 2008 10:28 AM, Ran Gutin <manicmessiah at gmail.com> wrote:
> > (define (doublequoted-symbol? sym)
> >   (and (pair? sym) (eqv? (car sym) 'quote)))
> >
> > (define-syntax match
> >   (syntax-rules ()
> >     ((match vars [pfirst prest ...] body ...)
> >
> >      (cond
> >
> >         ((and (not (doublequoted-symbol? (quote pfirst)))
> >              (symbol? (quote pfirst)))
> >         (let ((pfirst (car vars)))
> >           (match (cdr vars) [prest ...] body ...)))
> >
> >        ((eqv? pfirst (car vars))
> >         (match (cdr vars) [prest ...] body ...))
> >
> >        (else #f)))
> >
> >     ((match vars [] body ...) (begin body ...))))
> >
> > (match '(1 2 3) (one 2 three)
> >   (display three))
> >
> >
> >
> > Sorry for not commenting on the code, but here's a basic idea of what it
> > SHOULD do:
> > (match '(1 2 3) (1 2 3) (display 3)) should match perfectly and display
> 3 on
> > the terminal (it doesn't).
> > (match '(1 2 3) (one two three) (display 3)) works perfectly, and prints
> 3.
> > (match '(1 2 3) ('one 'two 'three) (display 'one)) - This should fail to
> > match the pattern altogether, as symbols which are already quoted are
> > matched for equality, rather than used as identifiers as above. This
> dies
> > miserably without returning #f.
> > (match '(1 2 3) (one 2 three) (display three)) - This should immediately
> > create an alias for the values 1 and 3 ('one' and 'three) and match the
> > second values for equality. Unfortunately, this is not the case.
> >
> >
> >  (match '(1 2 3) (one 2 three)
> >    (display three))
> > ... gives the following error:
> > "let: bad syntax (not an identifier) in: 2"
> >
> > It seems to be completely ignoring the conditional.
> > So I performed a test:
> > (and (not (doublequoted-symbol? (quote 2)))
> >              (symbol? (quote 2)))
> > ... actually returns FALSE. So then why is the conditional statement
> > branching off completely wrong?
> >
> > And then, here's the real kill. I can't debug the damn thing.
> >  Doing so sends an alert window flying in my face, and a larger one
> behind
> > it.
> >
> > "rest: expected argument of type <non-empty list>; given ()
> >
> >  === context ===
> > C:\Program Files\PLT\collects\mzlib\list.ss:295:2: rest
> > C:\Program Files\PLT\collects\mztake\debug-tool.ss:804:10: can-step-out?
> >
> > rest: expected argument of type <non-empty list>; given ()
> >
> >  === context ===
> > C:\Program Files\PLT\collects\mzlib\list.ss:295:2: rest
> > C:\Program Files\PLT\collects\mztake\debug-tool.ss:804:10: can-step-out?
> >
> > rest: expected argument of type <non-empty list>; given ()
> >
> >  === context ===
> > C:\Program Files\PLT\collects\mzlib\list.ss:295:2: rest
> > C:\Program Files\PLT\collects\mztake\debug-tool.ss:804:10: can-step-out?
> >
> > rest: expected argument of type <non-empty list>; given ()
> >
> >  === context ===
> > C:\Program Files\PLT\collects\mzlib\list.ss:295:2: rest
> > C:\Program Files\PLT\collects\mztake\debug-tool.ss:804:10: can-step-out?
> >
> > rest: expected argument of type <non-empty list>; given ()
> >
> >  === context ===
> > C:\Program Files\PLT\collects\mzlib\list.ss:295:2: rest
> > C:\Program Files\PLT\collects\mztake\debug-tool.ss:804:10: can-step-out?
> >
> > rest: expected argument of type <non-empty list>; given ()
> >
> >  === context ===
> > C:\Program Files\PLT\collects\mzlib\list.ss:295:2: rest
> > C:\Program Files\PLT\collects\mztake\debug-tool.ss:804:10: can-step-out?
> >
> > rest: expected argument of type <non-empty list>; given ()
> >
> >  === context ===
> > C:\Program Files\PLT\collects\mzlib\list.ss:295:2: rest
> > C:\Program Files\PLT\collects\mztake\debug-tool.ss:804:10:
> can-step-out?"
> >
> > ^ Can someone tell me what the hell is going on?
> >
> > _________________________________________________
> >   For list-related administrative tasks:
> >   http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> >
> >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.racket-lang.org/users/archive/attachments/20080119/10b0915d/attachment.html>