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From: peter@ficc.uu.net (Peter da Silva)
Newsgroups: comp.lang.forth
Subject: Re: New Directions: Forth is not postfix
Message-ID: <2.71SW6xds13@ficc.uu.net>
Date: 21 Jan 90 21:29:19 GMT
References: <284.UUL1.3#5129@willett.UUCP>
Reply-To: peter@ficc.uu.net (Peter da Silva)
Organization: Xenix Support, FICC
Lines: 48

> One of the things that is an annoying inconsistency is that
> Forth is not fully postfix.  The words ':', 'IF', 'DO', 'ELSE'
> etc. are prefix.  Has anyone out there done real postfix forth?

Adobe did. It's called Postscript.

Oddly enough, I did something like this a while ago, using the same
syntax as Postscript. Before I'd ever heard of said language.

> IF ELSE THEN might be:

>     else-addr then-addr condition IF-THEN-ELSE

	{ stuff } { stuff } cond ifelse

> IF THEN might be:

>     then-addr condition IF-THEN

	{ stuff } cond if

> One of the benefits to this is that UNLOOP is just a plain exit.

	Yes.

> One of the drawbacks to this is that it highlights Forth's lack of paradigm
> for doing controlled exits of more than just the immediately enclosing
> construct....

> ... {{ ... EXIT-:-WE-ARE-IN CheckError IF-THEN ... }} 100 0 ITERATE ...

(vaguely postscripty forth:)

	sizeof jumpbuf allocate 'status define

	{	bunch
		{	of
			{	nested
				{ stuff } while
				{ true status longjmp } something if
			} exec
		} status setjmp 0= if
	} 'new_word define

(actually throw and catch are better names, but longjmp/setjmp should be more
familiar to the large number of C hacks on Usenet)

So, do we call this "SIXTH"?
-- 
 _--_|\  Peter da Silva. +1 713 274 5180. <peter@ficc.uu.net>.
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