I think they are macro bindings that are actually structures with
prop:procedure functions, so that the app macro (like 'special') below, can
check where they came from.
#lang racket
(struct example (f x)
#:property
prop:procedure
(λ (e y)
((example-f e) (example-x e) y)))
(define a (example + 4))
(a 5)
(begin-for-syntax
(require racket/list)
(struct macro-example (f x)
#:property
prop:procedure
(λ (e y)
((macro-example-f e)
(macro-example-x e)
y))))
(define-syntax macro-a
(macro-example
(λ (now then)
#`(+ #,now #,@(rest (syntax->list then))))
#'4))
(macro-a 5)
(define-syntax (special stx)
(syntax-case stx ()
[(_ f e)
(macro-example? (syntax-local-value #'f (λ () #f)))
#'(f e)]
[_
#'42]))
(special macro-a 5)
(special a 5)
On Mon, Nov 5, 2012 at 6:49 AM, Grant Rettke <gret...@acm.org> wrote:
>
> On Mon, Nov 5, 2012 at 7:22 AM, Jay McCarthy <jay.mccar...@gmail.com>wrote:
>
>> every top-level define (like for 'f') has a special notation on it that
>> says "I'm a function". Since 'a' doesn't have this, then the macro for app
>> in BSL can throw an error.
>>
>
> What Racket language feature is used to do that?
>
>
--
Jay McCarthy <j...@cs.byu.edu>
Assistant Professor / Brigham Young University
http://faculty.cs.byu.edu/~jay
"The glory of God is Intelligence" - D&C 93
____________________
Racket Users list:
http://lists.racket-lang.org/users
