<!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 6.00.6000.16890" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT face="Courier New" size=2>Use datum->syntax for unhygienic macros:</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 (define-my-id stx)<BR> (syntax-case stx ()<BR>  ((_ id)<BR> #`(define<BR>  #,(datum->syntax stx<BR>     (string->symbol<BR>      (string-append "my-id-"<BR>       (symbol->string (syntax->datum #'id)))))<BR>    (lambda () (display 'id))))))</FONT></DIV> <DIV> </DIV> <DIV><FONT face="Courier New" size=2>(define-my-id trout)</FONT></DIV> <DIV> </DIV> <DIV><FONT face="Courier New" size=2>(my-id-trout) ; --> void, displaying trout</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>Jos</FONT></DIV> <DIV><FONT face="Courier New" size=2></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=laurent.orseau@gmail.com href="mailto:laurent.orseau@gmail.com">Laurent</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A title=plt-scheme@list.cs.brown.edu href="mailto:plt-scheme@list.cs.brown.edu">PLT-Scheme Mailing List</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, September 26, 2009 8:34 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> [plt-scheme] #'(require help)</DIV> <DIV><BR></DIV>Hi all,<BR><BR>I timidly require your help on a simple macro I've been trying to do for some time now.<BR><BR>I usually prefer to do things myself, but I'm stuck.<BR><BR>Here's the thing :<BR>I have an identifier and I want to generate an identifier based on it but with a different name.<BR>(in fact I have lots of identifiers)<BR><BR>for example :<BR>(define-my-id trout) <BR>would generate the macro identifier my-id-trout that expands to, say, (display "trout").<BR>My concern is about using in the program an identifier that is not defined explicitly in the program file.<BR>This should be possible though, since this is partly what define-struct does, I suppose.<BR><BR><BR>With eval and quasi-quoting I can easily generate an approximation with a lambda'd form but Scheme won't let me use identifiers that are not explicitly defined (it works in the REPL though):<BR>(define (define-my-id id)<BR>  (eval `(define ,(string->symbol (string-append "my-id-" (symbol->string id))) <BR>        (lambda () (display ,(symbol->string id))))))<BR><BR>I also know that syntax-id-rules can generate expanding identifiers, but I can't use string-append et al in macros to generate a new id...<BR><BR>Also, where can I find some simple macro samples, other than in the guide ?<BR><BR>Thanks a lot,<BR>Laurent<BR><BR><BR> <P> <HR> <P></P>_________________________________________________<BR>  For list-related administrative tasks:<BR>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme<BR></BLOCKQUOTE></BODY></HTML>