Path: utzoo!attcan!uunet!husc6!uwvax!oddjob!rfl
From: rfl@oddjob.UChicago.EDU (Bob Loewenstein)
Newsgroups: comp.lang.forth
Subject: Re: Local variables
Message-ID: <14992@oddjob.UChicago.EDU>
Date: 8 Aug 88 15:23:29 GMT
References: <8808060008.AA10585@jade.berkeley.edu>
Organization: U of Chicago - Astronomy & Astrophysics
Lines: 11


Implementing local variables and named input parameters
for a 68000 machine can be done by creating a third stack
using one of the address registers. Cells are transferred
from the parameter stack to the variable stack at the beginning
of the word execution and local names are assigned to the
location on the variable stack.  All subsequent references
simply do an indexed read to the appropriate stack address and
plop the variable back to the top of the parameter stack for
processing. For many words, the reduced parameter stack manipulation
(rot, dup, over, etc.) makes up for the initial overhead.