On Sun, 30 Nov 2014 22:21:14 +0100
Manfred Lotz <manfred.l...@arcor.de> wrote:
> No I hadn't considered the variant using type?. Thanks for this.
>
> Not quite sure if I'm happy about it as I would prefer to have the
> type checking at one place instead of providing a type each time I
> check/use options.
>
Saying this I think I like this version:
(define-syntax-rule (optval s ol)
(let ([found (assoc s ol)])
(if found
(let ([val (cdr found)])
(case s
['size (assert val integer?)]
['dir (assert val string?)]
['verbose (assert val boolean?)]
[else (error "Forgot to check in optval: option" s)]))
(error "not found"))))
--
Manfred
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