Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!umbc3!umbc5.umbc.edu!cs472226
From: cs472226@umbc5.umbc.edu (David Wood (CS472226))
Newsgroups: comp.lang.forth
Subject: The most fantastically fun word in FORTH ever!
Message-ID: <1993@umbc3.UMBC.EDU>
Date: 5 May 89 13:27:30 GMT
References: <3219@cosmo.UUCP>
Sender: newspost@umbc3.UMBC.EDU
Reply-To: cs472226@umbc5.umbc.edu.UUCP (David Wood (CS472226))
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Organization: University of Maryland Baltimore Co.
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   Okay, maybe I heaped on the adverbs a little too thick.
   But I've recently rediscovered my favorite word in FORTH! Sure, you
could talk about WISC hardware and the latest version of FORTH for x
system, but how often can one word provoke such enthusiasm?
   The word is, in GS16FORTH:
   : myself LATEST PFA CFA , ; immediate
   What this does is during compilation of a word, it takes the Name
Field Address of the most recently entered word (which would be the one
you're compiling when this appears [LATEST]), gets its Parameter Field
Address [PFA], gets its Code Field Address from that [CFA], then
compiles it into the dictionary [,]. The [immediate] after it means the
word is executed rather than compiled during the compilation phase.
   The result: The word's CFA is compiled into the word itself. Instant
recursion! The word now calls itself! Used indiscriminately, it will do
such nasty things as infinite loops, blown stacks, and other
heinousness.
   Error handling in the form of compilation-only protection is
forthcoming (no pun intended), but if you're just a little careful, I'm
sure there are people here who can find all sorts of wonderful ways to
abuse it, and I want to hear about every one! 

                                                    -David Wood
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