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Re: Why is FUNC in cl-callf not allowed to be an expression?

From: Stefan Monnier
Subject: Re: Why is FUNC in cl-callf not allowed to be an expression?
Date: Thu, 09 May 2019 20:47:48 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)

> I wonder why the FUNC argument in cl-callf is restricted to symbols (and
> lambda expressions, though this is not documented).  I don't see any
> reason to disallow arbitrary expressions, besides, maybe, that symbols
> would become ambiguous.

`callf` has been in cl.el "for ever" but it's not in Common-Lisp, so
I don't really know where it comes from.  I agree that when I moved it
to cl-lib, I missed an opportunity to fix it and make it take a normal
expression as first argument.

> I really would like to have an gv-callf that would simply interpret the
> function argument as an expression.  cl-callf just saves the programmer
> from typing the #' but forbids many use cases.

FWIW, you can circumvent this with

    (cl-flet ((f <EXPR>))
      (cl-callf f ...))

> I think I would even like it most like this:
> (defmacro gv-callf (call &optional n)
>   (gv-letplace (_getter setter) (nth (or n 1) call)
>     (funcall setter call)))

It's cute, tho I'm not too fond of specifying the place via a number,


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