On 05/21/2012 10:06 AM, Jon Rafkind wrote: > On 05/21/2012 06:02 AM, Matthew Flatt wrote: >> At Sun, 20 May 2012 22:42:30 -0600, Jon Rafkind wrote: >>> The issue is why do I have to use a name other than 'name' for the >>> pattern variable on the line where it says 'HERE'. If I use the >>> 'name' pattern variable then the syntax-parse form generated by >>> 'make-transformer' will use the wrong lexical context for the literal >>> set. I don't see how the lexical context of the outer 'name' differs >>> from the inner 'new-name', other than the 'new-name' has an extra >>> mark on it. >> When you use `name' instead of `new-name', then `name' gets replaced by >> `x' from the use of `define-new-syntax', and `x' (unlike `name') has a >> different lexical context than `new-name'. >> > > I thought that too but while debugging it didn't seem to be the case. If I > put a printf in the 'make-transformer' macro to "see" what name is being > passed in then using 'name' or 'new-name' as the pattern variable results in > the same thing being printed. > > (begin-for-syntax > (define-syntax (make-transformer stx) > (syntax-parse stx > [(_ name pattern template) > (printf "Name is ~a\n" #'name) > #'#'(lambda (stx) > (syntax-parse stx > #:literal-sets ([literals #:at name]) > [pattern template]))]))) > > > Then calling 'make-transformer' 3 different ways: > > (lambda (stx) > (syntax-parse stx > [(_ new-name) > (with-syntax ([output (make-transformer name pattern template)]) > #'(define-syntax new-name output))] > > "Name is #<syntax:x.rkt:56:19 x>", where line 56 is the use-site of > 'define-new-syntax' > > (lambda (stx) > (syntax-parse stx > [(_ name) > (with-syntax ([output (make-transformer name pattern template)]) > #'(define-syntax name output))] > "Name is #<syntax:x.rkt:56:19 x>"
I guess this case doesn't print #<syntax:x.rkt:39 x> because the 'name' at the use-site of 'make-transformer' is not bound by the pattern variable 'name'. If that is the case then it seems this case should be identical to the 1st case where it uses a different pattern variable, 'new-name'.
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