<HTML><BODY>Thank you! Sat, 28 Jun 2014 09:41:38 +0200 от "Jos Koot" <jos.koot@gmail.com>: <blockquote style="margin: 10px; padding: 0px 0px 0px 10px; border-left-color: rgb(8, 87, 166); border-left-width: 1px; border-left-style: solid;"> <div> <div class="js-helper js-readmsg-msg"> <style type="text/css"></style> <div> <base href="https://e.mail.ru/" target="_self"> <div id="style_14039413160000000654_BODY">#lang racket (define-syntax (set!-values* stx) (syntax-case stx () ((_ (var ...) values-expr) (with-syntax (((local-var ...) (generate-temporaries #'(var ...)))) #'(let-values (((local-var ...) values-expr)) (set!* var local-var) ...))))) (define-syntax (set!* stx) (syntax-case stx () ((_ var val) (free-identifier=? #'var #'_) #'foid) ((_ var val) #'(set! var val)))) (define foid (void)) (define-values (a b c) (values 1 2 3)) (set!-values* (_ _ c) (values 4 5 6)) (list a b c) Jos ________________________________ From: users [mailto:users-bounces@racket-lang.org] On Behalf Of Roman Klochkov Sent: sábado, 28 de junio de 2014 8:43 To: Racket Users List Subject: [racket] Please help with syntax I need to define syntax set!-values*, that will ignore _ in value place. Such as (define a #f) (set!-values* (_ _ a) (values 1 2 3)) ; should set a to 3. But I have two problems: 1. _ don't want to pattern match in syntax case. If I make it literal, I can't match "anything else". 2. How to omit extra values. It seems that in any case I have to assign them to something... Can you help me? I hope, that my problem in fact not hard, but I have not enough experience to solve it. -- Roman Klochkov </div> <base href="https://e.mail.ru/" target="_self"> </div> </div> </div> </blockquote> -- Roman Klochkov </BODY></HTML>