[gambit-list] Possible bug in define-macro
Marc Feeley
feeley at iro.umontreal.ca
Sun Apr 10 07:35:00 EDT 2011
Adding a trace inside your macro definition makes the problem obvious:
> (define-macro (pushnew item lst . test)
(let ((result
(let ((== (gensym)))
`(let ((,== ,(if (null? test) equal? (car test))))
(if (not (member ,item ,lst ,==))
(set! ,lst (cons ,item ,lst)))))))
(pp result)
result))
> (pushnew 5 flist)
(let ((#:g1 #<procedure #2 equal?>))
(if (not (member 5 flist #:g1)) (set! flist (cons 5 flist))))
*** ERROR IN (console)@15.1 -- Ill-formed expression
> (define-macro (pushnew item lst . test)
(let ((result
(let ((== (gensym)))
`(let ((,== ,(if (null? test) 'equal? (car test))))
(if (not (member ,item ,lst ,==))
(set! ,lst (cons ,item ,lst)))))))
(pp result)
result))
> (pushnew 5 flist)
(let ((#:g2 equal?))
(if (not (member 5 flist #:g2)) (set! flist (cons 5 flist))))
Marc
On 2011-04-09, at 3:30 PM, William James wrote:
> Gambit v4.6.1
>
>> (include "~/srfi-1-reference.scm")
>> (member 2 (iota 5) =)
> (2 3 4)
>> (define-macro (pushnew item lst . test)
> (let ((== (gensym)))
> `(let ((,== ,(if (null? test) equal? (car test))))
> (if (not (member ,item ,lst ,==))
> (set! ,lst (cons ,item ,lst))))))
>>
> (define flist '(2 3 5))
>>
> (pushnew 5 flist)
> *** ERROR IN (console)@21.1 -- Ill-formed expression
>>
>
>
> This macro works properly in Guile (and Bigloo):
>
> guile> (load "test-pushnew.scm")
> (2.0 8 2 3 5)
>
> where test-pushnew.scm is
>
> (define-macro (pushnew item lst . test)
> (let ((== (gensym)))
> `(let ((,== ,(if (null? test) equal? (car test))))
> (if (not (member ,item ,lst ,==))
> (set! ,lst (cons ,item ,lst))))))
>
> (define flist '(2 3 5))
>
> (pushnew 5 flist)
>
> (pushnew 8 flist)
>
> (pushnew 2.0 flist)
>
> (pushnew 3.0 flist =)
>
> (write flist) (newline)
>
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