On 27-Jan-09, at 2:34 PM, eryiling wrote:

suppose I have:

(define-macro (foo ...))

the standard way to 'debug' this is to do:

(pp (lambda () (foo ...)))

however, this requires that (foo ...) expands to proper scheme code (i.e. not things like "(a b . c)"), and also code that has well defined semantic meaning (i.e. no undefined vars)

as i write macros, i find that most of the time (in fact, except for the starting point and the ending point), my macro expansion offten results in non-scheme code; is there a way i can see this output? i.e. I wnat to see:

(macroexpand '(foo ...))

rather than the particular error for why (foo ... ) does not expand to legit scheme code

thanks!

Here's the trick I often use. Say you have the macro definition:

(define-macro (foo x y) ...something...)

you simply add a (list 'quote ...) around the body of your macro:

(define-macro (foo x y) (list 'quote ...something...))

Then when you can do

(pp (foo 1 2))

and this will print the s-expression that ...something... generated.

For example:

% gsi Gambit v4.4.0

(define-macro (bind var val expr)

(list 'quote `(let ((,var ,val)) ,expr)))

(pp (bind x (+ 1 2) (* x x)))

(let ((x (+ 1 2))) (* x x))

Once you are done debugging, you strip off the (list 'quote ...) wrapper.

Marc