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Re: definitions in macros?
From: |
David Kastrup |
Subject: |
Re: definitions in macros? |
Date: |
Sun, 22 Mar 2020 22:09:25 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
Han-Wen Nienhuys <address@hidden> writes:
> Hi there,
>
> in my quest to get lilypond working with GUILE 2+, I've hit another
> stumbling block.
>
> In order to make compilation with GUILE 2+ working, we have to move
> away from runtime symbol definition (ie. module-define! calls).
>
> In the code below, it looks like only one of the two definitions in
> the body of my-macro-new takes effect. Is this expected, and if so,
> why?
>
> (defmacro-public my-macro-old (command-and-args . definition)
> (module-define! (current-module) 'x1 "I am X1\n")
> (module-define! (current-module) 'x2 "I am X2\n"))
>
> (defmacro-public my-macro-new (command-and-args . definition)
> `(define p "i am P\n")
> `(define q "i am Q\n"))
This is very much expected. The macro body contains two side-effect
free expressions (namely quoted lists) and returns the last one which is
(define q "i am Q\n")
This then gets evaluated at run time, defining q .
You probably wanted something like
`(begin (define p ...) (define q ...))
as your body (and return expression) instead.
> (my-macro-old 1 2)
> (my-macro-new 1 2)
> (display x1)
> (display x2)
> (display q)
> (display p)
>
>
> thanks,
--
David Kastrup