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From: joel@decwrl.UUCP (Joel McCormack)
Newsgroups: net.lang.mod2
Subject: Re: FOR i := 1 TO 0
Message-ID: <360@decwrl.UUCP>
Date: Mon, 28-Jan-85 18:35:38 EST
Article-I.D.: decwrl.360
Posted: Mon Jan 28 18:35:38 1985
Date-Received: Wed, 30-Jan-85 08:26:25 EST
Organization: DEC Western Software Lab, Los Altos, CA
Lines: 25


    Wirth is not particularly clear, but no, FOR i := 1 TO 0 does not execute
the loop body.  He did not DEFINE the FOR loop in terms of REPEAT, but showed
how (what would be) a very common case of REPEAT is more appropriately
expressed with a FOR loop.

    The examples for minimum and sort would not work for very small arrays if
the FOR loop body always executed.

    The report in the back of the book is somewhat clearer, when it says that
"A+nC is the last term not exceeding B".  This implies to me that if A > B,
the loop body is not executed.

    Incidentally, it used to be that

    VAR i: 1..10;

    made it illegal to do

    FOR i := 1 TO 0, because of the limits were supposed to be assignment
compatible with the control variable.  This has been relaxed to merely
compatible.  This change should be in the 3rd edition of the book.

-- 
- Joel McCormack {ihnp4|decvax|ucbvax|allegra|sequent|utcsrgv}!decwrl!joel