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Re: How many arguments to a macro transformer?



Keith Wright wrote:

 > The short form is wonderful; we should keep it just as it is.
 > 
 > (1) It is not possible to make the relation of long form to short
 > form for |define-syntax| exactly parallel to that for |define|
 > without major changes to the language.  Given that they must be
 > different, it is less likely to cause confusion if the difference
 > is large.
 > 
 > (2) It is a long tradition that a macro has one argument which is
 > bound to the entire form of the macro call.  I think that both
 > LISP 1.5 and Common Lisp do it that way.
 
 Thank you - more good reasons supporting the current choice.  
  
 > The appendix of R4RS says that it has been suggested (it doesn't
 > say by whom) that #'<datum> and #`<datum> would be felicitous
 > abbreviations for (syntax <datum>) and (quasisyntax <datum>).
 > Could this be added to the SRFI?
 
 I will add that as a recommendation in the next revision.
 
 > Since |syntax| is already analogous to |quote|, is |syntax-quote|
 > really the right name for the third way?  If I understood it
 > better, I might be able to name it better.  How about
 > |syntax-reuse|?
 
 Good point.  Another possibility could be |syntax-verbatim|.  
 I'm also considering dropping this one, since it can be defined as a macro
 (although admittedly a rather ugly macro involving a compile-time
 data structure - hmm).     
 
 > As a stylistic matter, I think it would be better to remove uses
 > of |syntax-case| and |with-syntax| from the examples, except
 > where comparison with |syntax-case| is the point of the example.
 
 > In particular, the example given under the description of
 > |syntax-quote| is confusing because it requires a rather deep
 > understanding of |syntax-case| in order to follow.  A better
 > example would be built out of the the forms defined by the
 > SRFI only.  I bet it would actually come out shorter that
 > way, but I won't venture to try to make the example this
 > close to midnight.  It would also help to have two examples,
 > identical except that one uses |syntax| and the other
 > uses |syntax-quote| with different results.
 
 Since |syntax-case| is included in the new revision,
 it is probably okay to use it in examples where the pattern
 matching makes things clearer.  Where it doesn't, as in the |syntax-quote|
 example you raise, I'll work on rewriting them.    
 
 By the way, my justification for including the |syntax-case| form, even 
 though it is not a primitive, has not been well documented yet.  
 So here goes:  
 
   * I am specifying an improvement in the semantics of syntax-case
     for better hygiene.
     
   * A proposal that does not come with some form of pattern matching 
     won't be regarded as usable by many Schemers.  
   
   * For R5RS compatibility, we need to provide syntax-rules.  
     Syntax-case implies syntax-rules, and since the implementation 
     of syntax-case is only a few lines longer than that of syntax-rules,
     the implementation cost of including syntax-case is negligible.   

 > The link to Andrew Wright's pattern matcher
 >  http://download.plt-scheme.org/.../match.ss
 > at the end of kffd-match-tut.htm seems to be broken.
 
 Thank you - I removed it.  
 
 Cheers
 Andre