[Openmcl-devel] OpenMCL 1.0, compilation units and macroexpansion bug?

Vyacheslav Akhmechet coffeemug at gmail.com
Sun Nov 11 01:05:14 UTC 2007


Thanks! I'll add &environment. I already use it in most places, I just
misunderstood what the spec said about DEFMACRO.

Regards,
Slava Akhmechet

On 11/10/07, Gary Byers <gb at clozure.com> wrote:
> See section "3.2.3.1.1 Processing of Defining Macros" in the ANSI CL
> spec; there may be another section where this is discussed in more
> detail, but I can't find it at the moment.
>
> Basically, implementations are allowed to process defining-macros
> (like DEFMACRO) that appear in files being compiled in several ways.
> In DEFMACRO's case, They can:
>
> (a) make the macroexpansion function available globally,
> (b) add it to the lexical environment so that it's visible in the rest of
> the compilation, or
> (c) both.
>
> OpenMCL generally tries to do (b).  Many other implementations tend to
> do (a).  Both behaviors are correct (though I think that OpenMCL's is
> more useful.)
>
> If you want a macro definition to be accessible "in the global environment"
> (in the case of your example, don't want to have to use &environment),
> you can portably do:
>
> (eval-when (:compile-toplevel ...)
>    (defmacro ...))
>
> If you -wanted- to restrict the compile-time side-effects to (b) above ...
> well, I can't think of a good way to do this (which is part of the
> reason that I think that (b) is better default behavior.)
>
>
> On Sat, 10 Nov 2007, Vyacheslav Akhmechet wrote:
>
> > My apologies, adding &environment and passing the value to
> > macroexpand-1 explicitly *does* make a difference. Does that mean that
> > all other implementations support behavior that isn't required by the
> > spec?
> >
> > On 11/10/07, Vyacheslav Akhmechet <coffeemug at gmail.com> wrote:
> >> Hello,
> >>
> >> I'm running OpenMCL 1.0 on PPC. I'm having trouble with the following
> >> test snippet:
> >>
> >> (defmacro foo (a)
> >>   `(+ ,a ,a))
> >>
> >> (defmacro bar ()
> >>   `(print ',(macroexpand-1 '(foo 5))))
> >>
> >> (defun baz ()
> >>   (bar))
> >>
> >> When run from the REPL, calling (baz) returns (+ 5 5), as expected.
> >> However, when the definitions are placed into a file OpenMCL returns
> >> (foo 5), while all other implementations I've tested on return (+ 5
> >> 5). It seems that OpenMCL doesn't add the macro FOO to the null
> >> environment when MACROEXPAND-1 is called manually. I tried passing
> >> &environment explicitly, but got the same result.
> >>
> >> The spec for DEFMACRO says: "If a defmacro form appears as a top level
> >> form, the compiler must store the macro definition at compile time, so
> >> that occurrences of the macro later on in the file can be expanded
> >> correctly." Is this a bug or am I misunderstanding the spec?
> >>
> >> Regards,
> >> Slava Akhmechet
> >>
> > _______________________________________________
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> > Openmcl-devel at clozure.com
> > http://clozure.com/mailman/listinfo/openmcl-devel
> >
> >
>



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