Re: Trouble trying to understand how low level macros interact with module system.

On Wed, Dec 3, 2008 at 1:24 PM, Igor Hjelmstrom Vinhas Ribeiro
<[email protected]> wrote:
>> based on your definition, with little or no rewriting.
>
>
>    That's approximately what I would expect. But what I don't understand is
> why this s-expression that was created is not able to use the "thefunc"
> (since
> it is defined in the environment in which I am executing it).
>
>    To put it another way: I would expect that the expression resulting from
> the
> macro call "(thefunc)" would be executed in the exact same way (and in
> the exact same environment) as if I had typed "(thefunc)" - so it would
> work,
> even though it is executing outside the module context...
>
>    However, when I type (thefunc) it works, but when the macro "types it" it
> doesn't. I was considering the macro would either execute in the context of
> the module (and it would work) or in the same context I am typing (and it
> would also work)... if that is not the case, in which context is it
> executing?

Well, if (thefunc) was defined in the top level, this should be true.
However, (thefunc) defined in the module is actually bound to a
gensym'ed symbol.  So when the macro is invoked, and it produces a
literal |thefunc| instead of the gensymed version, it fails.  When you
do it however, your expression is run through the syntax expander, and
since the module is imported, your |thefunc| is renamed to the
gensymed version and works.

At least this is what I think is happening. :)

Scott
>
> Regards,
>  Igor.
>
>
>>
>> On Sun, Nov 30, 2008 at 6:44 AM, Igor Hjelmstrom Vinhas Ribeiro
>> <[email protected]> wrote:
>> > Hello, Mike - thanks for the reply!
>> >
>> >    Unfortunately, however, this also doesn't work[1]:
>> >
>> >    Any other clue on what could be wrong?
>> >
>> > Regards,
>> >  Igor.
>> >
>> > [1]. See below - trying Mike's suggestion. As before, calls to
>> > amacro fail stating that thefunc is undefined, while direct calls
>> > to thefunc work just fine.
>> >
>> > SISC (1.16.6)
>> > #;> (max-stack-trace-depth 16)
>> > 0
>> > #;>
>> > #;> (amacro)
>> > Error: undefined variable 'thefunc'.
>> > ---------------------------
>> > Some stack trace entries may have been suppressed. To see all entries
>> > set
>> > the dynamic parameter suppressed-stack-trace-source-kinds to '().
>> > #;> (thefunc)
>> >
>> >
>> > ---
>> >
>> > #;>
>> >
>> > On Sat, Nov 29, 2008 at 23:53, Mike J. Bell <[email protected]> wrote:
>> >>
>> >> Try:
>> >>
>> >> (module ((thefunc) (amacro thefunc))
>> >>   (define-macro amacro (lambda () (thefunc)))
>> >>   (define (thefunc) (display "\n\n---\n\n")))
>> >>
>> >> This (I think) means make an anonymous module with two exported
>> >> symbols,
>> >> thefunc and amacro (which depends on thefunc).
>> >>
>> >> Somebody else can I'm sure give you a better theoretical reason why
>> >> this
>> >> works (and what it really means, and why yours does what it does, which
>> >> isn't very intuitive to me off hand).
>> >>
>> >> Mike
>> >>
>> >>
>> >> On Sat, Nov 29, 2008 at 8:02 PM, Igor Hjelmstrom Vinhas Ribeiro
>> >> <[email protected]> wrote:
>> >>>
>> >>> Hello!
>> >>>
>> >>>    I am trying to understand how the module system used by SISC
>> >>> interacts with the low-level macros that SISC supports.
>> >>>
>> >>>   Specifically, I am trying to figure out why the follow snippet of
>> >>>   code, an anonymous module that exports amacro and thefunc,
>> >>>   doesn't work.
>> >>>
>> >>>    (module (amacro thefunc)
>> >>>      (define-macro amacro (lambda () (thefunc)))
>> >>>      (define (thefunc) (display "\n\n===\n\n")))
>> >>>
>> >>>   After I pasted it in the REPL, when I call (amacro) I get:
>> >>>
>> >>>    #;> (amacro)
>> >>>    Error: undefined variable 'thefunc'.
>> >>>    console:16:7: <indeterminate call>
>> >>>
>> >>>   Curiously, if I just go ahead and type (thefunc) it works:
>> >>>
>> >>>    #;> (thefunc)
>> >>>
>> >>>
>> >>>    ===
>> >>>
>> >>>    #;>
>> >>>
>> >>>    Is anyone able to explain to me why this happens?
>> >>>
>> >>> Regards,
>> >>>  Igor.
>> >>>
>> >>>
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>> >>
>> >>
>> >>
>> >> --
>> >> Mike J. Bell on gmail
>> >
>> >
>> >
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