Does this work? It uses a helper function, `prune`, to parse the var-val
clauses.
#lang racket
(define-for-syntax (prune stx)
(syntax-case stx ()
[()
#'()]
[((var val) others ...)
(cons #'(var val)
(prune #'(others ...)))]
[(var others ...)
(cons #'(var #f)
(prune #'(others ...)))]))
(define-syntax (aux stx)
(syntax-case stx ()
[(_ terms ...)
(with-syntax ([((var val) ...) (prune #'(terms ...))])
#'(define-values (var ...) (values val ...)))]))
(aux a (b (* 2 pi)) c (d pi))
a
b
c
d
;; output shown below
#f
6.283185307179586
#f
3.141592653589793
On Thursday, May 23, 2019 9:41:17 PM PDT Kevin Forchione wrote:
> Hi guys,
> I’ve been wracking my brains all day trying to come up with a macro that
> would convert this syntax:
>
> ;; (aux a (b (* 2 pi)) c (d pi))
> ;; => (define-values (a b c d) (values #f 6.28318530717958 #f
> 3.141592653589793)
>
>
> I’m missing some part of the picture. The closest I’ve come is to create a
> list of the pairs:
>
> #lang racket
>
> (define-syntax (aux stx)
> (syntax-case stx ()
> [(_ (var val)) #'`((var ,val))]
> [(_ var) #''((var #f))]
> [(_ (var0 val0) var1 ...) #'(append `((var0 ,val0)) (aux var1 ...))]
> [(_ var0 var1 ...) #'(append '((var0 #f)) (aux var1 ...))]))
>
> (aux a (b (* 2 pi)) c (d pi)) ;=> '((a #f) (b 6.283185307179586) (c #f) (d
> 3.141592653589793))
>
>
> Any help is greatly appreciated!
>
> Kevin
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