Re: `max-specpdl-size' and `max-lisp-eval-depth'

[Stephen Berman]

On Sun, 26 Sep 2021 23:01:17 +0800 Hongyi Zhao <hongyi.zhao@gmail.com> wrote:

> On Sun, Sep 26, 2021 at 9:04 PM Eli Zaretskii <eliz@gnu.org> wrote:
>>
>> > From: Hongyi Zhao <hongyi.zhao@gmail.com>
>> > Date: Sun, 26 Sep 2021 19:26:22 +0800
>> > Cc: help-gnu-emacs <help-gnu-emacs@gnu.org>
>> >
>> > what puzzles me most is what is the full English name of the word
>> > `specpdl'.
>>
>> As I recently learned, PDL = push-down list.
>
> Thank you for your explanation. Only two built-in symbols in Emacs
> contain this string in their names - the other is
> `ar-max-specpdl-size'.

The term goes back to the beginnings of Lisp (McCarthy's paper from
1960, available via the Wayback Machine from
http://www-formal.stanford.edu/jmc/recursive/node4.html):

  In general (we shall discuss an exception), the routine for a
  recursive function uses itself as a subroutine [...] This possible
  conflict is resolved by the SAVE and UNSAVE routines that use the
  public push-down list.

A footnote here (added later) says: "1995: now called a stack"

Steve Berman