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From: ForthNet@willett.pgh.pa.us (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Conditionals !
Message-ID: <2470.UUL1.3#5129@willett.pgh.pa.us>
Date: 7 Mar 91 03:41:50 GMT
Organization: (n.) to be organized.  But that's not important right now.
Lines: 40


   To: B.RODRIGUEZ2 [BRAD]           Refer#: 1389
 From: RAY DUNCAN                      Read: NO
 Subj: OPERATING SYSTEMS             Status: PUBLIC MESSAGE
 Conf: FORTH (58)                 Read Type: GENERAL (+)

    Brad writes:
    >If I were voting, I'd go with [IF] [ELSE] [THEN]
    >Are these words nestable
    >Can these words range across multiple screens linked with -->
    >Can these words be used both in compile and interpret state

 1.  I support this, it seems reasonable.  LMI isn't going to draw a line
 in the sand over the naming ".IF" etc.

 2.  They are nestable in the current version of LMI systems, but they
 weren't nestable in their first incarnations, so a lot of users don't
 take advantage of the nesting.

 3.  They don't span screens linked by --> in LMI systems, but they will
 work for collections of screens loaded with THRU (the implementation of
 .IF in our systems is basically to call WORD repeatedly looking for
 .ELSE or .THEN, with a little extra logic to support recursion).

 4.  .IF etc. are immediate and work in either interpreting or compiling
 mode.  However if you want to control compilation with a flag you have
 to make that flag IMMEDIATE, obviously, e.g.

    TRUE CONSTANT DEBUG? IMMEDIATE
    ...
    : FOOBAR     ...   DEBUG?  .IF  ...   .THEN ...  ;

 Ray Duncan, LMI

 NET/Mail : LMI Forth Board, Los Angeles, CA (213) 306-3530
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