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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.unix.programmer, comp.lang.misc
Subject: Re: On Stack-Based Languages (was Re: on Perl)
Date: Thu, 18 Apr 2024 07:55:42 -0000 (UTC)
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On Wed, 17 Apr 2024 08:05:23 -0700, John Ames wrote:

> *Syntactically* it's very simple, but explicit stack-orientation with
> reverse-Polish notation is a *very* different programming paradigm than
> practically everything else out there ...

The only really tricky part of stack-based programming is keeping track of 
what’s on the stack.

I did some messing about with a reboot of PostScript which tried to add 
some niceties, like stack guards and lexical binding. Here’s an example of 
the sort of thing I was able to get working (“ddef” and “dstore” define 
and assign to dynamically-bound variables, while “ldef” and “lstore” 
correspondingly work on lexically-bound ones):

    /Count 99 ddef

    /metatry
        { % provides context for nonlocals
            dup
            /Name exch ldef
            /Count 0 ldef
            { % actual proc
                /Count dup lload 1 add lstore
                /Count dup dload 1 add dstore
                Name =
                (local Count = ) print /Count lload =
                (global Count = ) print /Count dload =
                (whichever Count = ) print Count =
            }
        }
    ddef

    /try1 metatry ddef
    /try2 metatry ddef

    try1
    try2
    try1
    try2

Output:

    try1
    local Count = 1
    global Count = 100
    whichever Count = 1
    try2
    local Count = 1
    global Count = 101
    whichever Count = 1
    try1
    local Count = 2
    global Count = 102
    whichever Count = 2
    try2
    local Count = 2
    global Count = 103
    whichever Count = 2