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From: wmb@MITCH.ENG.SUN.COM
Newsgroups: comp.lang.forth
Subject: ANS NOT
Message-ID: <9007040412.AA28121@ucbvax.Berkeley.EDU>
Date: 3 Jul 90 18:42:37 GMT
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Reply-To: wmb%MITCH.ENG.SUN.COM@SCFVM.GSFC.NASA.GOV
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I'm concerned that some harsh evaluations may be based on misunderstandings:


>The one that really galls me is NOT. For twenty years 'NOT' has been a
>simple boolean 'NOT'.

Forth-79 says:
	NOT	( flag -> ! flag )  Reverse truth value.  Equivalent to 0=.

Forth-83 says:
	NOT	( 16b1 -- 16b2 )    16b2 is the one's complement of 16b1

Quoting from Kelly and Spies _FORTH: A Text and Reference_, p34:

	There is another word, NOT , whose use is inconsistent in different
	dialects of FORTH.  In most dialects and in FORTH-79, NOT doesn't
	change bits; it does something quite different ... .  In FORTH-83,
	however, NOT changes each bit to its opposite.

ANS Forth didn't change or "kill" NOT .  Forth-83 changed (and thus
ultimately killed) NOT .  ANS Forth simply noted that the damage has
already been done, and is beyond repair, unless you are willing to
break "most dialects" (as claimed in Kelly and Spies) of Forth.

Mitch Bradley