<!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 6.00.6000.16674" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT face="Courier New" size=2>Correct. _ has become a wild-card that is bound to a syntax that does not want to be called. You can no longer use _ like other symbols. Hence the wild card may appear in a pattern, but you should not use it in a template. That is in R6RS or PLT 4. In 371 _ was just a symbol like any other one. Why in Pretty Big it still works as an ordinary symbol in old fashion, I don't know.</FONT></DIV> <DIV><FONT face="Courier New" size=2>If you want a symbol that is associated with the name of the syntax use anything else than a wild-card. The wild-card is not bound to a pattern element (except may be in Pretty Big, I don't know)</FONT></DIV> <DIV><FONT face="Courier New" size=2>Jos</FONT></DIV> <BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A title=yinso.chen@gmail.com href="mailto:yinso.chen@gmail.com">YC</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A title=jos.koot@telefonica.net href="mailto:jos.koot@telefonica.net">Jos Koot</A> </DIV> <DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=plt-scheme@list.cs.brown.edu href="mailto:plt-scheme@list.cs.brown.edu">pltscheme</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, June 24, 2008 3:31 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [plt-scheme] (v4) wildcard not allowed in expression</DIV> <DIV><BR></DIV>I used to write _ in the expression as a shorthand to the head of the pattern as follows:<BR><BR> <DIV style="MARGIN-LEFT: 40px; FONT-FAMILY: courier new,monospace">Welcome to DrScheme, version 371 [3m].<BR>Language: Pretty Big (includes MrEd and Advanced Student).<BR>> (define-syntax (and2 stx)<BR>  (syntax-case stx () <BR>    ((_ a b c d ...)<BR>     #'(_ a (_ b c d ...))) ;;; works <BR>    ((_ a b)<BR>     #'(if a b #f))))<BR>> (and2 #t #t #t)<BR>#t<BR>> (and2 #t #t #t #f)<BR>#f<BR></DIV><BR>In v4 - the above causes the error of "<SPAN style="FONT-FAMILY: courier new,monospace">_: wildcard not allowed as an expression in (_ #t (_ #t #f))</SPAN>".   I noticed this error using emacs & v4 on Linux.  <BR><BR>I tried to replicate it using DrScheme (on Windows) and found that with the Module language it will cause the same error, but if using legacy language of Pretty Big, it appears to be behave the same as in 37x. <BR><BR><BR> <DIV style="MARGIN-LEFT: 40px; FONT-FAMILY: courier new,monospace">Welcome to DrScheme, version 4.0 [3m].<BR>Language: Module; memory limit: 128 megabytes.<BR>> (and2 #t #t #f) ;; throw error <BR>. _: wildcard not allowed as an expression in: (_ #t (_ #t #f))<BR></DIV><BR> <DIV style="MARGIN-LEFT: 40px; FONT-FAMILY: courier new,monospace">Welcome to DrScheme, version 4.0 [3m].<BR>Language: Pretty Big (includes MrEd and Advanced Student); memory limit: 128 megabytes.<BR>> (and #t #t #f) ;; works<BR>#f<BR></DIV><BR><BR><BR> <DIV class=gmail_quote>On Mon, Jun 23, 2008 at 5:44 PM, Jos Koot <<A href="mailto:jos.koot@telefonica.net" target=_blank>jos.koot@telefonica.net</A>> wrote:<BR> <BLOCKQUOTE class=gmail_quote style="PADDING-LEFT: 1ex; MARGIN: 0pt 0pt 0pt 0.8ex; BORDER-LEFT: rgb(204,204,204) 1px solid"> <DIV bgcolor="#ffffff"> <DIV><FONT face="Courier New" size=2>May be you missed the fact that _ has become a wild-card.</FONT></DIV> <DIV><FONT face="Courier New" size=2>Jos</FONT></DIV> <DIV> <DIV></DIV> <DIV> <BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(0,0,0) 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal">----- Original Message ----- </DIV> <DIV style="BACKGROUND: rgb(228,228,228) 0% 50%; FONT: 10pt arial; font-size-adjust: none; font-stretch: normal; -moz-background-clip: -moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial"><B>From:</B> <A title=jos.koot@telefonica.net href="mailto:jos.koot@telefonica.net" target=_blank>Jos Koot</A> </DIV> <DIV style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>To:</B> <A title=yinso.chen@gmail.com href="mailto:yinso.chen@gmail.com" target=_blank>YC</A> ; <A title=plt-scheme@list.cs.brown.edu href="mailto:plt-scheme@list.cs.brown.edu" target=_blank>pltscheme</A> </DIV> <DIV style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>Sent:</B> Tuesday, June 24, 2008 2:39 AM</DIV> <DIV style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>Subject:</B> Re: [plt-scheme] (v4) wildcard not allowed in expression</DIV> <DIV><BR></DIV> <DIV><FONT face="Courier New" size=2>It works for me though:</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>#lang scheme</FONT></DIV> <DIV> </DIV> <DIV><FONT face="Courier New" size=2>(define-syntax x<BR> (syntax-rules ()<BR>  ((_ 1 _) 'one)<BR>  ((_ _ 2) 'two)))</FONT></DIV> <DIV> </DIV> <DIV><FONT face="Courier New" size=2>(x 1 monkey) ; one<BR>(x monkey 2) ; two</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>Welcome to DrScheme, version 4.0.0.1-svn16jun2008 [3m].<BR>Language: Module.</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>Jos</FONT></DIV> <BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(0,0,0) 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal">----- Original Message ----- </DIV> <DIV style="BACKGROUND: rgb(228,228,228) 0% 50%; FONT: 10pt arial; font-size-adjust: none; font-stretch: normal; -moz-background-clip: -moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial"><B>From:</B> <A title=yinso.chen@gmail.com href="mailto:yinso.chen@gmail.com" target=_blank>YC</A> </DIV> <DIV style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>To:</B> <A title=plt-scheme@list.cs.brown.edu href="mailto:plt-scheme@list.cs.brown.edu" target=_blank>pltscheme</A> </DIV> <DIV style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>Sent:</B> Tuesday, June 24, 2008 12:32 AM</DIV> <DIV style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>Subject:</B> [plt-scheme] (v4) wildcard not allowed in expression</DIV> <DIV><BR></DIV>Hi - <BR><BR>It seems that in v4 `_` can no longer exist in the expression position for syntax-case, is there a reason for the change? <BR><BR>Thanks,<BR>yc<BR><BR> <P></P> <HR> <P></P>_________________________________________________<BR>  For list-related administrative tasks:<BR>  <A href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme" target=_blank>http://list.cs.brown.edu/mailman/listinfo/plt-scheme</A><BR></BLOCKQUOTE> <P></P> <HR> <P></P>_________________________________________________<BR>  For list-related administrative tasks:<BR>  <A href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme" target=_blank>http://list.cs.brown.edu/mailman/listinfo/plt-scheme</A><BR></BLOCKQUOTE></DIV></DIV></DIV></BLOCKQUOTE></DIV><BR></BLOCKQUOTE></BODY></HTML>