Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!rochester!uhura.cc.rochester.edu!sunybcs!bingvaxu!vu0141
From: vu0141@bingvaxu.cc.binghamton.edu (vu0141)
Newsgroups: comp.lang.forth
Subject: Re: RepTil I am, therefore I was
Summary: An addedum
Message-ID: <1985@bingvaxu.cc.binghamton.edu>
Date: 9 Mar 89 15:09:06 GMT
References: <1980@bingvaxu.cc.binghamton.edu> <1983@bingvaxu.cc.binghamton.edu>
Reply-To: vu0141@bingvaxu.cc.binghamton.edu (Fred Schiff)
Organization: SUNY Binghamton, NY
Lines: 26

I forgot to mention it, but comments are included within the
definition.  It wasn't that important in what I was writing but NOW verbs
(Forth's IMMEDIATEs, except the verb NOW is placed after the DO: instead 
of after the end of the definition, which Urieli says is confusing) work
by doing their job and then compiling in a "dummy" verb which is usually
a no-op, (sometimes it has a job to do, of course) but which the decompiler
is smart enough to print out as the original verb.

Thus ?IFTRUE in a definition does its business with the return and symbol
stacks and compiles ?IFTRUE% the runtime word which tests the top of the
parameter stack when it is executed within a definition.  Upon decompilation
you get the original definition back.

The article, skips lots of the implementation details but does give
definitions for the inner and outer interpreter, and all of the structure
words.

Its token threaded by the way.  Or more accurately "status-threaded" meaning
that each word has a 16-bit header which has the definition's length (so
that they can be moved around in memory) and a number of bit-flags which
give information (NOW word, indent left/right in decompilation, ROM word
which should not be moved, etc.)  Also the names of words, code for words,
and data space for variables and constants are all kept in separate areas
of memory.

Fred Schiff (vu0141@bingvaxu.cc.binghamton.edu)