Re: Easy to add with push but not to the end of a list

[Emanuel Berg <incal@dataswamp.org>]

Michael Heerdegen wrote:

> Use `macroexpand' and/or `macroexpand-1' to check the
> expansion of macro calls. The rest is just...normal Elisp.
> You know how to write Elisp, so write it so that the
> expansion you want is generated. It's code returning code.
> So what's the code you want to produce?

I don't know, because this can't be done with Elisp, not any
Elisp I know anyway, since the variable name will then be
evaluated ...

Here is the `push' macro - TBH, I don't know what most of that
means ...

(defmacro push (newelt place)
  "Add NEWELT to the list stored in the generalized variable PLACE.
This is morally equivalent to (setf PLACE (cons NEWELT PLACE)),
except that PLACE is evaluated only once (after NEWELT)."
  (declare (debug (form gv-place)))
  (if (symbolp place)
      ;; Important special case, to avoid triggering GV too early in
      ;; the bootstrap.
      (list 'setq place
            (list 'cons newelt place))
    (require 'macroexp)
    (macroexp-let2 macroexp-copyable-p x newelt
      (gv-letplace (getter setter) place
        (funcall setter `(cons ,x ,getter))))))

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