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Re: unhandled constant?

From: Han-Wen Nienhuys
Subject: Re: unhandled constant?
Date: Sat, 1 Feb 2020 12:23:51 +0100

On Sat, Feb 1, 2020 at 11:11 AM David Kastrup <address@hidden> wrote:
> >> Here is an example that shows better how things work, and what might
> >> be the cause of my problems. Is it right that programmatically set
> >> contents of "current-module" are not serialized into the compiled
> >> file?
> >>
> >>    (define (run-at-compile-time cmd)
> >>      (module-define! (current-module) (string->symbol cmd) #t)
> >>      (format (current-error-port) "I-am-called-at-compile-time ~a\n" cmd))
> >>
> >>   (define (runtime-call cmd)
> >>     (format (current-error-port) "I-am-called-at-runtime ~a\n" cmd)
> >>     (format (current-error-port) "val ~a\n"
> >>             (module-ref (current-module) (string->symbol cmd))))
> >>
> >>   (defmacro foo (cmd . rest)
> >>   (run-at-compile-time cmd)
> >>   `(runtime-call ,cmd))
> >>
> >>   (foo "xy")
> >> ERROR: In procedure scm-error:
> >> No variable named xy in #<directory (guile-user) 56514b591140>
> >>
> But that is not using a local define at all.  Can you point out the
> actual code that failed for you?

There are two independent problems. One is a problem with inner
defines, which is addressed by

the symptom is compilation failing with "unhandled constant #<procedure ... > "

The other is a problem you can reproduce if you check out

with the symptom being:

;;; compiling 
fatal error: Not a markup command: line

This is because the LilyPond macro "markup" doesn't recognize markup
command and aborts in code that is executed at compile-time. The code
that triggers this are  definitions in scm/define-markup-commands.scm
that use (mark #:blah .. ) in the function body.

You can verify this by rewriting
and seeing how the error message changes.

I still don't understand why some code is executed compile time (the
expansion of the  markup macro) while other is not (defining the
make-x-markup function in (current-module))

Since we recognize markup commands by looking them up in
(current-module), I believe the example I showed here shows that we
can never make this work, and we  will have to revisit the markup
macros completely.

Han-Wen Nienhuys - address@hidden -

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