I would like to write a macro that accepts an optional keyword
argument. If the argument is missing, or if it is present and has a
true value, then some code will be generated. Otherwise, nothing is
done. This was my best attempt:
#lang racket
(require (for-syntax syntax/parse))
(define-syntax (foo stx)
(syntax-parse stx
[(foo name val (~optional (~seq #:make-double? make-double?:boolean)))
(with-syntax ([func (if (syntax->datum #'(~? make-double? #'#t))
#'(define (doubleup) (* 2 val))
#'(begin))])
#'func)]))
(foo x 6 #:make-double? #t)
doubleup
No joy. doubleup is never defined, no matter what happens with the
keyword. I'm not sure what I'm doing wrong -- any advice?
More generally, this feels like something for which there should be a
simpler solution. I think that ~? isn't quite what I'm looking for,
since the thing that I'm testing for defined/truth isn't going to be
used in the code that will actually be generated. What should I be
using?
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