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Re: Alternative formulations of keywords
On Apr 12, Marc Feeley wrote:
> Most Scheme systems allow separate compilation (think of "load").
> If one file contains:
> (define (f #!key (x 11) (y 22)) (+ x y))
> (define (g z) (f y: z))
> and the other contains:
> (set! f (lambda (#!key (y 33) (z 44)) (* y z)))
> You have the same problem. So it doesn't suffice for the function
> definition to be global.
IIUC, John's proposal can be implemented using modules in PLT as
(define (foo x #!key y z)
is translated to
(define (hidden-foo x y z)
(define-syntax (foo stx)
... analyze stx for keyword syntaxes, and construct a call for
... hidden-foo with plain arguments)
where hidden-foo is an identifier that is not accessible outside the
macro. When I wrote our library, I considered this approach, but it
seems like it's much less useful, basically a completely different
mechanism for only named arguments. It didn't take us long to reach
exactly this conclusion:
> The way I see it you are forbidding the use of higher-order functions
> in combination with named optional parameters. That would be a
> serious limitation for a functional language like Scheme.
((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay:
http://www.barzilay.org/ Maze is Life!