[armedbear-devel] Compiler macros vs source transforms
kpreid at mac.com
Tue Jul 14 00:22:16 UTC 2009
On Jul 13, 2009, at 17:04, Erik Huelsmann wrote:
> So, this is his take on it in XCL:
> * as the CLHS documents: there can only be 1 compiler-macro per symbol
> * the user is free to define his own compiler macros
> The two statements above mean that the (correct) operation of the
> compiler should not depend on any compiler macros.
> XCL uses source-transforms to make sure the user can define compiler
> macros for any symbol he or she likes.
Er, this would be true except for CLHS 188.8.131.52.2:
"Except where explicitly allowed, the consequences are undefined if
any of the following actions are performed on an external symbol of
the COMMON-LISP package:
3. Defining, undefining, or binding it as a macro or compiler macro.
(Some exceptions are noted below.)"
That is, the implementation may rely on compiler macro definitions for
There may be reasons to use a different mechanism than compiler-
macros, but user redefinition is not one of them.
Kevin Reid <http://switchb.org/kpreid/>
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