Oops, forgot to include the users list. _____
From: Jos Koot [mailto:[email protected]] Sent: miércoles, 06 de abril de 2016 23:03 To: 'Richard Adler' Subject: RE: [racket-users] macros within expressions. You don't need a macro here. Why not simply: (map point-y points) May be your example is an extract where you realy need a macro. In that case: (define-syntax y-coord (syntax-id-rules () [(y-coord lst) (map point-y lst)])) (y-coord points) You can't map a macro. You could make a macro-mapper though: (define-syntax-rule (map-macro macro arg) (map (λ (x) (macro x)) arg)) (define-syntax-rule (y-macro arg) (point-y arg)) (map-macro y-macro points) But in general it is wise to AVOID MACROS. Good luck, Jos -----Original Message----- From: [email protected] [ <mailto:[email protected]> mailto:[email protected]] Sent: miércoles, 06 de abril de 2016 22:27 To: Racket Users Subject: [racket-users] macros within expressions. I am trying to use a macro, y-coord, in the following way: (struct point (x y)) (define points (list (point 25 25) (point 33 54) (point 10 120)) (map y-coord points) I am expecting the result: '(25 54 120) and the error is "y-coord: bad syntax in: y-coord Here is the macro: (define-syntax y-coord (syntax-id-rules (map) [(map y-coord lst) (map (lambda (p) (point-y p)) lst)])) Can anyone help? Thanks -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit <https://groups.google.com/d/optout> https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
