rsw-elisp - Interactively evaluate regions, preceding variable definitions and quoted sexpressions

This code improves and replaces the GNU Emacs commands that interactively evaluate Emacs Lisp expressions. The new commands replace standard key bindings and are all prefixed with rsw-elisp-. They work the same way as the old commands when called non-interactively; only the interactive behavior should be different, as described below.

To set up to use this every Emacs session, first install this package with an Emacs package manager and then add the following to your Emacs initialization file:

(require 'rsw-elisp)
(rsw-elisp-enable)

Or you can test it out the remapped key bindings of all of the interactive Emacs Lisp evaluation commands and a few minibuffer helper commands, with:

M-x rsw-elisp-enable RET

To return to the standard key bindings, use:

M-x rsw-elisp-disable RET

To toggle this on and off, use:

M-x rsw-elisp-toggle RET

Programmatically, to see whether it is enabled or not, use:

(rsw-elisp-p)

---

The commands and key bindings herein provide 5 new features for interactive Emacs Lisp evaluation:

1. Evaluating Quoted Expressions: C-x C-e (eval-last-expression) on a regularly quoted sexpression doesn't show you anything different than what you see on screen already. You really want to see the value of the unquoted sexpression and now you can. C-x C-e (rsw-elisp-eval-last-expression) and M-: (rsw-elisp-eval-expression) remove any regular outer quotes from sexpressions and show you the value. For example, 'emacs-version interactively yields "26.0.50".

   This is for programmers who already understand how quoting works and don't need to see the same expression fed back to them. For times where you really need to see the quoted form, use a backquote ` or a backquote followed by a regular quote '.

2. Evaluating Function Symbols: When interactively evaluating a symbol, Emacs returns only the symbol's value, giving an unbound error if it is not defined. But if it is a function symbol in such a case, you typically want to see its function binding, so these functions return that when the symbol is bound as a function (or a macro) but not a variable.

3. Redefining Variables: Interactively calling eval-last-expression with point after a previously defined variable definition does not reset its value in Emacs, though clearly the only reason to do this is to redefine the variable. Although eval-defun does do this, there is no reason to have to use a different key binding than you would to interactively evaluate other expressions. C-x C-e (rsw-elisp-eval-last-expression) resolves this.

4. Default Expressions to Evaluate: When using M-: bound to (rsw-elisp-eval-expression), if a region is active, the leading expression in the region is used as the default expression to evaluate and included in the prompt. Otherwise, if called with point in an Emacs Lisp mode listed in rsw-elisp-modes and not on a whitespace character, then the expression around point is used as the default.

5. Editing Default Expressions: If you ever want to edit the default, use M-y (rsw-elisp-yank-pop) to yank it into the editable portion of the minibuffer, any time other than after a yank command. (M-y still performs its normal yank-pop function after a C-y yank command). If you yank in a large expression by mistake, press C-d or DELETE FORWARD when at the end of the minibuffer to erase its entire contents. If you prefer these helper keys not be bound, after the call to:

   (rsw-elisp-enable)
   

   add:

   (setq rsw-elisp-helper-keys nil)