[racket] keep bindings in unhygienic macros?
On Tue, Jul 19, 2011 at 3:16 PM, Ismael Figueroa Palet
<ifigueroap at gmail.com> wrote:
> Thanks Matthias and Sam, the macro expansion now works as I intended, with
> the following change:
>
> (define-syntax-rule (with-monad (<unit-f> <bind-f>) <body>)
> (let ((u <unit-f>)
> (b <bind-f>))
> (syntax-parameterize ([bind (make-rename-transformer #'b)])
> (syntax-parameterize ([unit
> (make-rename-transformer #'u)])
> <body>))))
You can write the above with just one use of `syntax-parameterize':
(define-syntax-rule (with-monad (<unit-f> <bind-f>) <body>)
(let ((u <unit-f>)
(b <bind-f>))
(syntax-parameterize ([bind (make-rename-transformer #'b)]
[unit (make-rename-transformer #'u)])
<body>)))
> 2011/7/19 Sam Tobin-Hochstadt <samth at ccs.neu.edu>
>>
>> On Tue, Jul 19, 2011 at 2:06 PM, Ismael Figueroa Palet
>> <ifigueroap at gmail.com> wrote:
>> > Hi all, I'm trying to implement some simple macros to use monads in
>> > racket
>> > using a Haskell-like do notation. I have the following macros, and my
>> > problem is that I want the do macro to capture the bind identifier
>> > created
>> > by with-monad, and in each recursive step of the do macro expansion keep
>> > the
>> > same identifier. I don't know it is possible, I tried using (with-syntax
>> > ((bind (datum->syntax 'bind) ))) but it doesn't work.
>>
>> I think the right solution here is to use syntax parameters [1]. This
>> blog post by Eli provides a good intro:
>> http://blog.racket-lang.org/2008/02/dirty-looking-hygiene.html
>>
>> [1] http://docs.racket-lang.org/reference/stxparam.html
>> --
>> sam th
>> samth at ccs.neu.edu
>
>
>
> --
> Ismael
>
>
--
sam th
samth at ccs.neu.edu
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