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Paste # 17412 | ||
2016-08-25 07:11:41 | ||
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#lang racket (require syntax/parse) (syntax-parse #'(#:a #:b #:c) [((~or (~once (~and a #:a)) (~once (~and b #:b)) (~once (~and #:c (~post (~fail #:when (and (attribute a) (attribute b) (attribute c))))))) ...) #t])