RE: apropos commands for commands, user options, all functions, all variables

[Drew Adams]

> > You can do (put 'set 'interactive-form
> >                 '(interactive "Svariable name: \nxValue: "))
> > and then M-x set RET <var> RET <val> RET
> > or just M-: (setq <var> <val>) RET
> > I implemented the functionality for the first, and I personally use the
> > second.
>
> Neither is as convenient as set-variable which
>
> 1. picks up the default variable name from the buffer;
> 2. provides completion;
> 3. provides the old value as default for editing in the minibuffer;

Exactly.

Someone will no doubt argue that you can anyway use M-TAB with `M-: (setq '
to complete Lisp symbols, including variables, but it's not the same level
of convenience at all.

Users should have available: (1) completion for only option names (with a
`set-option' command) and (2) completion for only (arbitrary) variable names
(with a redefined `set-variable' command). Completion of arbitrary Lisp
symbols is an undirected shotgun blast here.

Completion (`completing-read', not `lisp-complete-symbol') lets you deal
with the right set of thingies (domain), and can hand you a reasonable
default value to play with. There should be completion commands for setting
both options and arbitrary variables.