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From: Cary Jamison <cary@svl.trw.com>
Subject: Re: GNAT messages and the not operator (pitfall alert!)
Date: 1996/10/28
Message-ID: <3275A12F.B8F@svl.trw.com>#1/1
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references: <dewar.846162354@merv>
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Date: 1996-10-28T00:00:00+00:00
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Robert Dewar wrote:
[...]
RD> Consider this program, which we now, as you see, generate a warning for:
RD> 
RD>      1. with Text_IO; use Text_IO;
RD>      2. procedure t1 is
RD>      3.    type m is mod 256;
RD>      4.    a : m := 4;
RD>      5.    b : m := 5;
RD>      6. begin
RD>      7.     if not a < b then
RD>                |
RD>         >>> warning: operand of not operator should be parenthesized
RD> 
RD>      8.         Put_Line ("this is what I expect");
RD>      9.     else
RD>     10.         Put_Line ("but this is what I get!");
RD>     11.     end if;
RD>     12.
RD>     13.     if (not a) < b then
RD>     14.         Put_Line ("this is not what I expect");
RD>     15.     else
RD>     16.         Put_Line ("this is what I get, and I really asked for it!");
RD>     17.     end if;
RD>     18. end;
RD> 
RD> I think this warning is quite reasonable, since I would *really* like people
RD> to use parens if they really want the situation shown on line 13!

But, shouldn't the warning be "not expression should be parenthesized"?  I think
the "operand of not operator" would just be the 7, i.e. "not (7)" instead of "(not 7)".


-- 
Cary Jamison
TRW SIG
cary@svl.trw.com