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From: steve@jplgodo.UUCP (Steve Schlaifer x3171 156/224)
Newsgroups: net.lang.forth
Subject: Re: Recursion forth
Message-ID: <781@jplgodo.UUCP>
Date: Wed, 7-May-86 00:42:35 EDT
Article-I.D.: jplgodo.781
Posted: Wed May  7 00:42:35 1986
Date-Received: Sat, 10-May-86 14:18:22 EDT
References: <1854@mtgzz.UUCP> <2441@yale.ARPA> <439@cit-vax.Caltech.Edu>
Organization: Jet Propulsion Labs, Pasadena, CA
Lines: 38
Summary: don't forget to smudge before ;

In article <439@cit-vax.Caltech.Edu>, alfke@cit-vax.Caltech.Edu (J. Peter Alfke) writes:
> In FIG-influenced versions of FORTH, each word has a 'smudge' bit in its
> header.  This bit is normally off, but is set while the word is in the
> process of being defined.  The smudge bit inhibits recognition of the word
> in a dictionary search.
> 
> The purpose of this is to let you redefine a word and have references to
> the word call the old version, i.e.
> 
> 	: cr  crcount @ 1+ crcount ! cr ;	( keep track of cr's)
> 
> To defeat this in special cases (recursion), there's a word called
> 'smudge' which toggles this bit in the most-recently-defined word.
> So:
> 
> 	: fact   smudge
> 		...blah blah blah, including calls to fact which are
> 		   real recursive calls...
> 	;
> 
This is more or less correct.  However, SMUDGE is not usually IMMEDIATE
so you need to do a

: FACT [ SMUDGE ] ...blah blah blah

and when ; executes it will do a SMUDGE which toggles the bit so you need

: FACT [ SMUDGE ] ...blah blah blah  [ SMUDGE ] ;

Personally, I find the use of MYSELF clearer and less prone to errors like
forgetting the [ ] stuff needed above.
-- 

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