Comments on: Macro trial balloons http://4.flowsnake.org/archives/66 A Pythoneer's adventures with Chicken Scheme. ^_^ And more. Wed, 07 Jan 2009 00:41:27 +0000 http://wordpress.org/?v=2.6.5 By: Graham Fawcett http://4.flowsnake.org/archives/66#comment-110 Graham Fawcett Sat, 16 Feb 2008 21:45:01 +0000 http://4.flowsnake.org/archives/66#comment-110 Sure, absolutely. Sure, absolutely.

]]> By: Hans Nowak http://4.flowsnake.org/archives/66#comment-108 Hans Nowak Sat, 16 Feb 2008 13:30:27 +0000 http://4.flowsnake.org/archives/66#comment-108 Thanks, Graham. With your permission, I will use the new definition of inc! in the s1 code. Thanks, Graham. With your permission, I will use the new definition of inc! in the s1 code.

]]> By: Graham Fawcett http://4.flowsnake.org/archives/66#comment-105 Graham Fawcett Sat, 16 Feb 2008 05:02:42 +0000 http://4.flowsnake.org/archives/66#comment-105 You might also be interested in using pattern-matching in your macros. It's overkill for this example, but it's helpful when the arglist for your macro is complicated: (define-macro (inc! var . vals) (match vals (() `(set! ,var (+ 1 ,var))) (nums `(set! ,var (+ ,var ,@nums))))) The first clause matches when the vals list is emtpy, and the second clause ('nums') is an 'otherwise' clause -- nums matches the entire vals object (in this case, it must be a list of 1 or more elements). The match system is built into Chicken; search for 'pattern matching' in the manual. Very cool stuff. :-) You might also be interested in using pattern-matching in your macros. It's overkill for this example, but it's helpful when the arglist for your macro is complicated:

(define-macro (inc! var . vals)
(match vals
(() `(set! ,var (+ 1 ,var)))
(nums `(set! ,var (+ ,var ,@nums)))))

The first clause matches when the vals list is emtpy, and the second clause ('nums') is an 'otherwise' clause -- nums matches the entire vals object (in this case, it must be a list of 1 or more elements).

The match system is built into Chicken; search for 'pattern matching' in the manual. Very cool stuff. :-)

]]> By: Graham Fawcett http://4.flowsnake.org/archives/66#comment-104 Graham Fawcett Sat, 16 Feb 2008 04:54:08 +0000 http://4.flowsnake.org/archives/66#comment-104 You're working too hard for that inc! macro, I think. What about this: (define-macro (inc! var . vals) `(set! ,var (+ ,var ,@vals))) Wait, I see you want a case for an empty val-list. This would work, (define-macro (inc! var . vals) `(set! ,var (+ ,var ,@(if (null? vals) '(1) vals)))) The gensym stuff is important when you want to avoid a name collision, but in your case, there's no need for an intermediate variable, so no gensyms are required. You're working too hard for that inc! macro, I think. What about this:

(define-macro (inc! var . vals)
`(set! ,var (+ ,var ,@vals)))

Wait, I see you want a case for an empty val-list. This would work,

(define-macro (inc! var . vals)
`(set! ,var (+ ,var
,@(if (null? vals)
'(1) vals))))

The gensym stuff is important when you want to avoid a name collision, but in your case, there's no need for an intermediate variable, so no gensyms are required.

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