First note there is more than one code/macro expander for Gambit: Gambit's default, the one with Black Hole, and the syntax-case library file, for instance.
2012/8/26 Bob McIsaac bobmc_net@rogers.com
Hi:
3 questions...
I'm looking for a "when" macro and tried one patterned on "unless". It behaves like "when-not". How do I write a proper "when" macro?
(define-syntax when-not (syntax-rules () ((when-not test body ...) (if test #t (begin body ...)))))
(define (test-when n) (when-not (not (< n 50)) (println "line1 " n) (println "line2 " n) (println "line3 " n))) (test-when 0) (test-when 3) (test-when 55) ;-------------------------------------------
I'm not clear about what you are trying to achieve here.
Re "define-syntax" the Gambit-C manual says .."Note that this implementation of syntax-case does not support special forms that are specific to Gambit." What are the implications of this statement? Is there a preferred model for writing Gambit-C macros?
No support for #!rest #!optional #!key would be a good start. Not clear atm about more.
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Some code has a "##" prefix like.. (##define-macro (err form) `(let () (##declare (safe) (generic)) (err-form (lambda () ,form))))
Why is that?
Generally in Gambit ##-prefixes on Gambit-provided procedures is to say it's the non-typechecked variant.
As for Gambit-provided syntactical forms (##define-macro ##lambda etc.) I believe they're equivalent with the non-prefixed variant.
Brgds
=bob=
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