Bengt Kleberg <bengtk@damek.kth.se> wrote:
+---------------
| I have a question about 5.3 Syntax Definitions. ...in 5.3 the
| (define-syntax <keyword> <transformer spec>)
| "template" is never explained with an example.
+---------------

Probably because it was considered too simple to need an example,
since Section 4.3.1 "Binding constructs for syntactic keywords" had
already given several examples of "let-syntax", and it really *is* the
case that "define-syntax" is to "let-syntax" as "define" is to "let"[*].

In any event, here's a corresponding "define-syntax" for the first
"let-syntax" example given in 4.3.1:

	(define-syntax when (syntax-rules ()
			      ((when test stmt1 stmt2 ...)
			       (if test
				 (begin stmt1 stmt2 ...)))))

As you see, all of the complexity is in the definition of
"<transformer spec>" (Section 4.3.2 "Pattern language"),
which is the same whether it's in a "define-syntax" or
a "let-syntax" or a "letrec-syntax".

+---------------
| Instead there is a (let-syntax ....) example.
+---------------

Actually, there's a "let-syntax" *NON*-example,  ;-}  ;-}
because it's specifically stated to be an example
of an error (erroneous shadowing of a keyword).


-Rob

[*] O.k., o.k., "define" is closer to "letrec" than to "let". So sue me.

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Rob Warnock, 7L-551		rpw3@sgi.com   http://reality.sgi.com/rpw3/
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