On 11/17/2011 01:24 PM, Jon Rafkind wrote:
On 11/17/2011 01:20 PM, Ryan Culpepper wrote:
On 11/17/2011 12:28 PM, Jon Rafkind wrote:
I have some code that deconstructs and reconstructs a syntax object. I'm
pretty sure this code is at fault for not adding the proper lexical
context back on so I get an error about 'no #%app bound'.
(syntax-parse form
[(form ...)
(with-syntax ([(form* ...) (map honu->racket (syntax->list #'(form ...)))])
(datum->syntax forms
#'(form* ...)
forms
forms))]
I had hoped that datum->syntax would add the original lexical context
back on, is it not doing what I hoped?
No, the datum->syntax there is a no-op, because #'(form* ...) is already a syntax
object, and datum->syntax stops when it hits something that's already a syntax
object.
You should do something like this instead:
(datum->syntax forms
(map honu->racket (syntax->list #'(form ...)))
forms
forms)
Ok thanks, that solved the problem. For future reference if I have a more
complicated use case is there a way to put the original lexical context back on
the new syntax object?
If such a function could exist it should go into unstable/syntax since I keep
forgetting how to reconstruct the lexical context.
FWIW converting a syntax object to a list and then passing that to
datum->syntax works as well.
(with-syntax ([(form* ...) (map honu->racket (syntax->list #'(form ...)))])
(datum->syntax forms (syntax->list #'(form* ...)) forms forms))
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