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Re: Bug with macros in SCM and Guile


From: Aubrey Jaffer
Subject: Re: Bug with macros in SCM and Guile
Date: Mon, 15 Jan 2007 21:26:07 -0500 (EST)

 | From: Kevin Ryde <address@hidden>
 | Date: Tue, 16 Jan 2007 09:35:50 +1100
 | 
 | Aubrey Jaffer <address@hidden> writes:
 | >
 | >  | From: Marc Feeley <address@hidden>
 | >  | Date: Wed, 29 Nov 2006 15:58:57 -0500
 | >  | 
 | >  | For SCM it seems that a macro call is normally expanded when
 | >  | an expression is encountered in a top-down traversal of the
 | >  | code, but not always.  For example, in the function bar2 below
 | >  | the macro call to foo is expanded when bar2 is *called*, and
 | >  | at that point a new definition of the macro foo has been
 | >  | introduced.
 | 
 | I thought that was the idea for defmacro, to expand when it runs,
 | and in fact to re-expand every time it's run.  A little wasteful,
 | but it's emulating lisp style (or is it just emacs-lisp style) in
 | that isn't it?

Looking at
http://www.cs.cmu.edu/Groups/AI/html/hyperspec/HyperSpec/Body/mac_defmacro.html
I don't see where it requires repeated evaluation.




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