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Re: c99 and the lack of warnings when int operations are applied to a bool

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Le 23/03/12 23:48, Ian Collins a écrit :
> On 03/24/12 11:29 AM, jacob navia wrote:
>> Le 23/03/12 23:17, Robert Wessel a écrit :
>>> Yet the language has always allowed the results of logical or
>>> relational operators to be used arithmetically. How do you define a
>>> rule that continues to allow that but disallows the use of _Bools?
>>
>> The rule could be simply:
>>
>> Only boolean operations are allowed with bools: or, and, xor, not. If
>> you want to do arithmetic with bools you store that into an int (or
>> long double or whatever) and then you go on from there.
>>
>> Or you make a cast.
>>
>> There shouldn't be any *implicit* conversions.
>
> Isn't assigning a _Bool to an int an implicit conversion?
>

Yes it is, but I am speaking about arithmetic operations like
multiplication and division.

Those operations have no meaning with bools.


bool a,b;

a*b |  1  |  0 |
------------------
0   |  0  |  0 |
1   |  1  |  0 |

a/b is a division by zero if b is zero. If b is one,
then it is a NOP.

a/b |  1  |  0 |
------------------
0   |  0  | NAN|  <<< UB
1   |  1  | NAN|  <<<<UB



Mmmm substration looks like xor isn't it?

a-b |  1  |  0 |
------------------
0   |  1  |  0 |
1   |  0  |  1 |

Addition:

a+b |  1  |  0 |
------------------
0   |  1  |  0 |
1   |  1  |  1 |

This means that those operations with booleans are with VERY high
probability ERRORS.

And if you substitute in the truth tables integer values (ANY integer
values) the results are equally weird. There is no point in doing those
operations and they are simply errors.

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c99 and the lack of warnings when int operations are applied to a bool mathog <dmathog@gmail.com> - 2012-03-23 08:40 -0700
  Re: c99 and the lack of warnings when int operations are applied to a bool James Kuyper <jameskuyper@verizon.net> - 2012-03-23 12:07 -0400
  Re: c99 and the lack of warnings when int operations are applied to a bool jacob navia <jacob@spamsink.net> - 2012-03-23 21:45 +0100
    Re: c99 and the lack of warnings when int operations are applied to a bool Robert Wessel <robertwessel2@yahoo.com> - 2012-03-23 17:17 -0500
      Re: c99 and the lack of warnings when int operations are applied to a bool jacob navia <jacob@spamsink.net> - 2012-03-23 23:29 +0100
        Re: c99 and the lack of warnings when int operations are applied   to a bool Ian Collins <ian-news@hotmail.com> - 2012-03-24 11:48 +1300
          Re: c99 and the lack of warnings when int operations are applied   to a bool jacob navia <jacob@spamsink.net> - 2012-03-24 23:47 +0100
            Re: c99 and the lack of warnings when int operations are applied   to a bool Willem <willem@toad.stack.nl> - 2012-03-25 09:05 +0000
              Re: c99 and the lack of warnings when int operations are applied   to a bool "BartC" <bc@freeuk.com> - 2012-03-25 11:30 +0100
                Re: c99 and the lack of warnings when int operations are applied   to a bool Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-25 21:05 +0100
                Re: c99 and the lack of warnings when int operations are applied   to a bool Lowell Gilbert <lgusenet@be-well.ilk.org> - 2012-03-25 16:15 -0400
                Re: c99 and the lack of warnings when int operations are applied   to a bool Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-25 22:14 +0100
                Re: c99 and the lack of warnings when int operations are applied   to a bool James Kuyper <jameskuyper@verizon.net> - 2012-03-25 23:46 -0400
                Re: c99 and the lack of warnings when int operations are applied to a bool Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-26 12:05 +0100
                Re: c99 and the lack of warnings when int operations are applied to a bool Lowell Gilbert <lgusenet@be-well.ilk.org> - 2012-03-26 15:22 -0400
              Re: c99 and the lack of warnings when int operations are applied to a bool Gareth Owen <gwowen@gmail.com> - 2012-03-25 11:44 +0100
                Re: c99 and the lack of warnings when int operations are applied to a bool Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-25 13:06 +0100
            Re: c99 and the lack of warnings when int operations are applied to a bool Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-27 11:12 -0700
        Re: c99 and the lack of warnings when int operations are applied to a bool Robert Wessel <robertwessel2@yahoo.com> - 2012-03-24 01:15 -0500
          Re: c99 and the lack of warnings when int operations are applied to a bool jacob navia <jacob@spamsink.net> - 2012-03-24 23:29 +0100
    Re: c99 and the lack of warnings when int operations are applied to a bool mathog <dmathog@gmail.com> - 2012-03-27 09:53 -0700
      Re: c99 and the lack of warnings when int operations are applied to a bool Keith Thompson <kst-u@mib.org> - 2012-03-27 11:07 -0700
      Re: c99 and the lack of warnings when int operations are applied to a bool James Kuyper <jameskuyper@verizon.net> - 2012-03-27 14:16 -0400
      Re: c99 and the lack of warnings when int operations are applied to a bool Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-04-26 07:57 -0400
        Re: c99 and the lack of warnings when int operations are applied to a bool jacob navia <jacob@spamsink.net> - 2012-04-26 14:08 +0200
        Re: c99 and the lack of warnings when int operations are applied to a bool James Kuyper <jameskuyper@verizon.net> - 2012-04-26 09:09 -0400
          Re: c99 and the lack of warnings when int operations are applied to a bool Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-04-26 21:29 -0400
            Re: c99 and the lack of warnings when int operations are applied to a bool James Kuyper <jameskuyper@verizon.net> - 2012-04-26 21:58 -0400
              Re: c99 and the lack of warnings when int operations are applied to a bool Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-04-26 22:32 -0400
                Re: c99 and the lack of warnings when int operations are applied to a bool James Kuyper <jameskuyper@verizon.net> - 2012-04-27 06:31 -0400
                Re: c99 and the lack of warnings when int operations are applied to a bool ImpalerCore <jadill33@gmail.com> - 2012-04-27 08:31 -0700

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