* Using the content of a dynamic variable in a macro
@ 2023-02-24 6:31 Damien Cassou
2023-02-26 11:47 ` Michael Heerdegen
0 siblings, 1 reply; 2+ messages in thread
From: Damien Cassou @ 2023-02-24 6:31 UTC (permalink / raw)
To: help-gnu-emacs
Hi,
I'm wondering why the code below works but won't compile.
foo.el:
(defvar foo-var '((message "hello world")))
(defmacro foo-macro ()
`(progn
,@foo-var))
(defun foo-fun ()
(foo-macro))
$ emacs --batch -l foo.el --eval '(foo-fun)'
hello world
$ emacs --batch --eval '(find-file "foo.el")' --eval '(emacs-lisp-byte-compile)'
In toplevel form:
foo.el:32:1: Error: Symbol’s value as variable is void: foo-var
Why isn't the compiler aware of the foo-var variable?
--
Damien Cassou
"Success is the ability to go from one failure to another without
losing enthusiasm." --Winston Churchill
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Using the content of a dynamic variable in a macro
2023-02-24 6:31 Using the content of a dynamic variable in a macro Damien Cassou
@ 2023-02-26 11:47 ` Michael Heerdegen
0 siblings, 0 replies; 2+ messages in thread
From: Michael Heerdegen @ 2023-02-26 11:47 UTC (permalink / raw)
To: Damien Cassou; +Cc: help-gnu-emacs
Damien Cassou <damien@cassou.me> writes:
> I'm wondering why the code below works but won't compile.
>
> foo.el:
> (defvar foo-var '((message "hello world")))
>
> (defmacro foo-macro ()
> `(progn
> ,@foo-var))
>
> (defun foo-fun ()
> (foo-macro))
> [...]
> foo.el:32:1: Error: Symbol’s value as variable is void: foo-var
>
> Why isn't the compiler aware of the foo-var variable?
The compiler is aware of it, but it doesn't eval the definition. It is
a feature that the compiler normally does not load any part of the
program when compiling, including variable definitions. Note that in
the general case, evaluating a defvar form might require to load more
parts of a file, or even the complete file.
If you do need to eval something when compiling, use `eval-when-compile'
or `eval-and-compile' respectively.
Michael.
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