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Re: Alternative formulations of keywords Eli Barzilay 12 Apr 2006 13:36 UTC

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:
                         Maze is Life!