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) ;-------------------------------------------
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? ;------------------------------------------------------------
Some code has a "##" prefix like.. (##define-macro (err form) `(let () (##declare (safe) (generic)) (err-form (lambda () ,form))))
Why is that?
=bob=
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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.
;------------------------------------------------------------
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=
Gambit-list mailing list Gambit-list@iro.umontreal.ca https://webmail.iro.umontreal.ca/mailman/listinfo/gambit-list
On 08/26/2012 06:49 PM, Mikael wrote:
I'm not clear about what you are trying to achieve here.
Thanks, Mikael, for your helpful reply. In addition to understanding Gambit specifics, I was trying to create WHEN. I finally found a couple of examples in "Teach Yourself Scheme in Fixnum days" .. they both work although quoted version needed adjustment.
(define-macro _when ;; alternate version (lambda (test . branch) (list 'if test (cons 'begin branch))))
(define-macro when (lambda (test . branch) `(if ,test {IF and BEGIN from the example uppercase did not work} (begin ,@branch))))
=Bob=
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 mailto: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.
;------------------------------------------------------------ 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= || _______________________________________________ Gambit-list mailing list Gambit-list@iro.umontreal.ca <mailto:Gambit-list@iro.umontreal.ca> https://webmail.iro.umontreal.ca/mailman/listinfo/gambit-list
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Bob McIsaac -
Mikael