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Re: Reintroducing old `defined?'
Russ McManus <firstname.lastname@example.org> writes:
> > Actually, in the large majority of cases it's *much* simpler to write
> > syntax-case macros than defmacros, and what is great about them is
> > that they work. They don't cause strange unexpected errors due to
> > identifier collisions.
> Yes, that has always been the promise.
It's actually more than a promise. Guile already has syntax-case
macros, although they aren't yet implemented on low-level.
Say (use-syntax (ice-9 syncase)) in a recent snapshot. (I think
there's some trouble with the use-syntax form in 1.3.)
(The above actually introduces a transformer which parses all code.
This is necessary to get 100% pure behaviour, but in most cases
(use-module (ice-9 syncase)) works as well, and doesn't require code
> > Many people got scared of hygienic macros after seeing the low-level
> > macro facility in R4RS. In addition to providing the easy-to-use
> > high-level facility from R5RS (`syntax-rules'), syntax-case macros
> > also support *easy-to-use* low-level power!
> But how do I learn them? I have a lovely learning device for
> defmacro's, Graham's 'On Lisp', but I couldn't find anything about how
> to pick up syntax-case.
Kent Dybvig has written a wonderful book "The Scheme Programming
Language" the 2nd ed. which has recently been published. This book
also exists on-line. Have a look at
> > Also, syntax-case macros integrate naturally with a
> > module-system---they don't insert undefined bindings into the
> > caller's code.
> I lost you here.
Module A exports
(defmacro foo (x)
Module B imports foo, but not bar.
(foo 'gurka) --> Error: bar undefined