The behavior of `set!' in the right-hand side of a `let-syntax' binding to mutate a `define-for-syntax'ed variable was completely broken. (Apparently, no one has ever tried that combination before.) I've pushed a fix.
At Tue, 16 Nov 2010 12:54:17 -0700, Jon Rafkind wrote: > On 11/16/2010 12:45 PM, Jon Rafkind wrote: > > `define-syntax' has different behavior from `let-syntax' when the > > transformer operates on top-level bindings in the transformer environment. > > > > (define-for-syntax foo 1) > > > > (define-syntax (x1 stx) > > (printf "z: foo is ~a\n" foo) > > (set! foo (add1 foo)) > > (printf "z: foo is ~a\n" foo) > > #'1) > > > > (x1) > > > > #; > > (let-syntax ([x1 (lambda (stx) > > (printf "z: foo is ~a\n" foo) > > (set! foo (add1 foo)) > > (printf "z: foo is ~a\n" foo) > > #'1)]) > > (x1)) > > > > With `define-syntax' I see > > z: foo is 1 > > z: foo is 2 > > > > But with `let-syntax' I see > > z: foo is 1 > > z: foo is 1 > > > > Is this a bug or am I missing something? > I guess it has to do with expansion order somehow. If I try to > interleave calls to a macro defined by `define-syntax' and the > `let-syntax' expression I see the `define-syntax' expansions happen first. > > (define-for-syntax foo 1) > > (define-syntax (x2 stx) > (printf "z: foo is ~a\n" foo) > (set! foo (add1 foo)) > (printf "z: foo is ~a\n" foo) > #'1) > (x2) > (let-syntax ([x1 (lambda (stx) > (printf "let z: foo is ~a\n" foo) > (set! foo (add1 foo)) > (printf "let z: foo is ~a\n" foo) > #'1)]) > (x1)) > > (x2) > > z: foo is 1 > z: foo is 2 > z: foo is 2 > z: foo is 3 > let z: foo is 3 > let z: foo is 3 > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
