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From: ForthNet@willett.pgh.pa.us (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Data Structures
Message-ID: <1723.UUL1.3#5129@willett.pgh.pa.us>
Date: 13 Sep 90 03:02:09 GMT
Organization: String, Scotch tape, and Paperclips.  (in Pgh, PA)
Lines: 44

Category 3,  Topic 20
Message 115       Wed Sep 12, 1990
D.RUFFER [Dennis]            at 00:29 EDT
 
Re: DARRYL BIECH

 > 1.) What is wrong with using the three conventional looping
 > constructs DO FOR, DO WHILE, and DO UNTIL, and combining them with
 > IF THEN (ELSE) to create the more complicated control structures

I don't rmember the comment you refer to, but what we now have, IMHO is very
close you what you are suggesting.  Forth uses different commands, so here are
the equivalents:

        Traditional        Forth
        DO FOR          -> DO LOOP
        DO WHILE        -> BEGIN WHILE REPEAT
        DO UNTIL        -> BEGIN UNTIL
        IF THEN (ELSE)  -> IF (ELSE) THEN

There seems to be a lot of confusion about how these individual operators can
be combined, and my understanding is that the current BASIS does not even
reflect what it should in this regard (i.e. what has already been passed by
the TC).  Perhaps only experimentation with a compliant system will tell the
real answer, but I have been assured that the following work:

        BEGIN WHILE UNTIL THEN

Thus creating a loop that has two exit points.  I made a proposal very early
in the proccess for a similar construction.  It was rejected in favor of the
more powerful generalizations that we have now.  I think that is what you are
looking for also.

 > 2.) Why not have counted strings that are optionally null-
 > terminated?

Tradition?  It would be a counted string if it was null-terminated. Why not
terminate strings with a $?  What about a user selectable character?  Where
would it all end?  :-)

DaR
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