Path: utzoo!attcan!uunet!wuarchive!zaphod.mps.ohio-state.edu!usc!ucsd!ucbvax!MITCH.ENG.SUN.COM!wmb
From: wmb@MITCH.ENG.SUN.COM
Newsgroups: comp.lang.forth
Subject: Interpret/compile consistency
Message-ID: <9009211313.AA26438@ucbvax.Berkeley.EDU>
Date: 20 Sep 90 15:30:35 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: wmb%MITCH.ENG.SUN.COM@SCFVM.GSFC.NASA.GOV
Organization: The Internet
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> The question I have at this point is what weight should be given to the
> consistency position you cite in your new-user case.  I assume you also
> have problems explaining why  IF  THEN    DO  LOOP  and so on also
> don't work if interpreted?

Not any more.  I fixed them so that they do work if interpreted.  It is
remarkably easy to do; the trick is to switch to compile state when the
beginning of a control structure is encountered, and execute the temporary
definition when that control structure is completed.  I wrote a paper about
this that was published in the 1987 (I think) FORML proceedings, and John
Hayes recently published an extension of same in Forth Dimensions (issue
before last).  The whole mechanism for interpreted conditionals adds 200
bytes to the Forth system.

The reason I was motivated to work out this interpreted control structure
scheme was because I was trying to explain to a new Forth user (who happens
to be a world-class C programmer) why control structures don't work in
interpret state.  He persisted in thinking it was stupid that Forth was
inconsistent in this respect, and I discovered that I agreed with him.
So I fixed it.

I would also note that >R and R> can be used in interpret state in the
latest version of my system.

Mitch