<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=iso-8859-1"> <META content="MSHTML 6.00.6000.16587" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff background=""> <DIV><FONT face="Courier New" size=2>The following is extracted and simplified as much as possible from a bigger piece of code.</FONT></DIV> <DIV><FONT face="Courier New" size=2>Sorry that I could not condence it any further.<BR><BR>; file lazy.ss ----------------------------------------<BR>(module lazy mzscheme<BR> (provide lazy)<BR> (define module-name (gensym 'module-name-lazy-))<BR> <BR> (define-syntax lazy<BR>  (syntax-rules ()<BR>   ((lazy expr) (lazy/proc 'expr))))<BR> <BR> (define (lazy/proc expr)<BR>  (let/cc cc<BR>   </FONT><FONT size=2><FONT face="Courier New"><FONT color=#ff0000>(eval<BR>    `(module ,module-name <BR>     "lazy-language.ss"<BR>     ,cc ,expr))</FONT>))<BR> <BR> ; inorder to make require superfluous<BR>  (lazy/proc 'initialize)<BR>  (eval `(require ',module-name)))</FONT></FONT></DIV> <DIV><FONT face="Courier New" size=2>  ; module name quoted for 3.99.0.9<BR><BR>; file lazy-language.ss ---------------------------------<BR>(module lazy-language mzscheme<BR> (provide macro scheme</FONT></DIV> <DIV><FONT face="Courier New" size=2>  (rename mod-begin #%module-begin)</FONT></DIV> <DIV><FONT face="Courier New" size=2>  (rename #%datum #%top)) ; allow free vars<BR> <BR> (define-syntax (macro stx) <BR>  (syntax-case stx ()<BR>   ((_ (id keywords rule ...) ... expr)<BR>    #'(letrec-syntaxes<BR>     (((id ...) (#%app values (syntax-rules keywords rule ...) ...)))<BR>     expr))))<BR> <BR> (define-syntax scheme<BR>  (syntax-rules ()<BR>   ((_ x) (#%app eval 'x))<BR>   ((_ x y ...) (#%app (#%app eval 'x) y ...))))<BR><BR> (define-syntax mod-begin<BR>  (syntax-rules ()<BR>   ((_ cont x)<BR>    (#%module-begin<BR>     (#%app (#%datum . cont) x))))))<BR><BR>; using the above -------------------------</FONT></DIV> <DIV><FONT face="Courier New" size=2>; definitions window<BR>(require "lazy.ss" )</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>(lazy<BR> (macro (a () ((a x y) (scheme list x y)))<BR>  (a p q))) ; --> (p q) ok</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>(lazy<BR> (macro (a () ((a x ...) (scheme list x ...)))<BR>  (a p q))) ; --> (p q) ok</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>(lazy<BR> (macro (a () ((a x ...) (scheme list x ...)))<BR>  (a p q r))) ; --> error: a: bad syntax in: (a p q r)</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>Run: interactions-window:</FONT></DIV> <DIV><FONT face="Courier New" size=2>Welcome to DrScheme, version 3.99.0.9-svn6jan2008 [3m].<BR>Language: Textual (MzScheme, includes R5RS)</FONT></DIV> <DIV><FONT face="Courier New" size=2>(p q)<BR>(p q)<BR>lazy.ss:12:3: a: bad syntax in: (a p q r)</FONT></DIV> <DIV><FONT face="Courier New" size=2>> </FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>This used to work in all earlier versions of MzScheme. Now many things have changed, I know. What change do I overlook? It seems like in the calls to syntax lazy, the ellipses are taken for a common identifier. Any help will be very much appreciated. I already tried to parse the rules given to syntax macro, replacing every occurrence of identifier '...' by a locally introduced ellipsis, but that did not help.</FONT></DIV> <DIV><FONT face="Courier New" size=2>Jos Koot</FONT></DIV></BODY></HTML>