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

[Michael Heerdegen]

Hello,

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.

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.

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)))

Example:

(let ((l (list 1 2)))
  (gv-callf (append l (list 3 4)))
  l)

=> (1 2 3 4)

(let ((l (list (list 'c 'd))))
  (gv-callf (append (list 'a 'b) (car l) (list 'e 'f)) 2)
  l)

=> ((a b c d e f))

That's simpler than current cl-callf, unites cl-callf and cl-callf2 in
something more general, and even eldoc still works in the CALL.


Michael.