Re: local syntax-rules

[Ivan Toshkov]

Ivan Toshkov writes:
 > Lars J. Aas writes:
 >  > On Mon, Nov 06, 2000 at 05:14:08PM +0100, Lars J. Aas wrote:
 >  > :   (define-syntax argtypes
 >  > :     (let-syntax ((argtype (syntax-rules ()
 >  > :                             ((argtype (name type)) type)
 >  > :                             ((argtype name) <top>))))
 >  > :       (syntax-rules ()
 >  > :         ((argtypes arg) (cons (argtype arg) '()))
 >  > :         ((argtypes arg arg1 ...) (cons (argtype arg) (argtypes arg1 
 > ...))))))
 >  > : 
 >  > : Should I use let-syntax in another way (e.g. *inside* the argtypes 
 > syntax-rules)?
 >  > 
 > 
 > Perhaps the problem is that syntax rules aren't first class scheme objects,
 > (don't know if it's true) and therefore let-syntax cannot evaluate to a 
 > syntax
 > rule. 

Oops! Totally wrong! Next time I'll know I have to check before I write :)
Syntax rules are procedures.

I'll try to come up with something...

 > 
 > On the other hand, in R5RS is said that there is no analog to local define 
 > for
 > synax definitions, so your problem seems to get tougher.
 > 
 >  > I found putting them inside the rules to work:
 >  > 
 >  >   (define-syntax argtypes
 >  >     (syntax-rules ()
 >  >       ((argtypes arg)
 >  >         (let-syntax ((argtype (syntax-rules ()
 >  >                                 ((argtype (name type)) type)
 >  >                                 ((argtype name) <top>))))
 >  >           (cons (argtype arg) '())))
 >  >       ((argtypes arg arg1 ...)
 >  >         (let-syntax ((argtype (syntax-rules ()
 >  >                                 ((argtype (name type)) type)
 >  >                                 ((argtype name) <top>))))
 >  >           (cons (argtype arg) (argtypes arg1 ...))))))
 >  > 
 >  > However, this makes me have to repeat the submacros for each public 
 > syntax-rule,
 >  > making the whole thing an unreadable mess.  Isn't a shared approach (like 
 > the
 >  > invalid example on top) possible?  I tried to enclose the syntax rules 
 > through
 >  > let-variables, but that didn't work either:
 >  > 
 >  >   (define-syntax argtypes
 >  >     (let ((argtype-rules (syntax-rules ()
 >  >                            ((argtype (name type)) type)
 >  >                            ((argtype name) <top>))))
 >  >       (syntax-rules ()
 >  >         ((argtypes arg)
 >  >           (let-syntax (argtype argtype-rules)
 >  >             (cons (argtype arg) '())))
 >  >         ((argtypes arg arg1 ...)
 >  >           (let-syntax (argtype argtype-rules)
 >  >             (cons (argtype arg) (argtypes arg1 ...)))))))
 >  > 
 >  > Any suggestions?  I'll rather use public sub-macros than the let-syntax 
 > approach
 >  > I found to work...
 >  > 
 > 
 > If I think of something I'll let you know :)  Meanwhile, why don't you try to
 > post your question in comp.lang.scheme and see what they have to say about 
 > it?
 > I guess most of the guile developers/users prefer lisp-style macros and 
 > that's
 > why you don't get many answers here...
 > 
 >  >   Lars J
 >  > 
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 >  > http://mail.gnu.org/mailman/listinfo/guile-user
 >  > 
 >