GNU bug report logs - #18821
25.0.50; Let pp-macroexpand-expression expand only once

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: bug-gnu-emacs <at> gnu.org
Subject: 25.0.50; Let pp-macroexpand-expression expand only once
Date: Sat, 25 Oct 2014 01:13:36 +0200

Hello,

this is a feature request.

The problem is the following:

When writing a complex macro, one often wants to check some examples to
see if it expands code as intended.

There are different ways of doing that: M-x pp-macroexpand-expression or
M-x emacs-lisp-macroexpand for example.

But there is a problem: if the macro expansion is a toplevel call to
some other macro, this one will also be expanded, because the above
commands use `macroexpand' which successively expands until the result
is not a macro call.  This is not useful for checking macro expansions.

I want to suggest to alter `pp-macroexpand-expression', or to provide a
new command, based on a function that expands only one time like

    (defun macroexpand1 (expr)
      (apply (cdr (symbol-function (car expr))) (cdr expr)))

(This can no doubt be improved, e.g. to DTRT for autoloaded macros.)


Or did I miss something?  Opinions?


Thanks,

Michael.





In GNU Emacs 25.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.14.1)
 of 2014-10-17 on drachen
Windowing system distributor `The X.Org Foundation', version 11.0.11601000
System Description:	Debian GNU/Linux testing (jessie)

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