On Tue, Sep 28, 2021 at 01:05:15PM +0200, Emanuel Berg via Users list for the GNU Emacs text editor wrote:

[...]

> IIRC from Automata Theory there was this thing called a PDA or
> "pushdown automaton", maybe that was a stack as well?

That was a stack. A PDA automaton is a finite automaton enhanced
by a stack, so it can grok nested structures.

Cheers
 - t