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Re: Range-aware modulo operator -%

Subject Re: Range-aware modulo operator -%
Newsgroups comp.lang.c
References (10 earlier) <q0e1qc$t3p$1@dont-email.me> <9RxWD.81420$N45.2557@fx21.am4> <lnd0phmcjw.fsf@kst-u.example.com> <O2zWD.105221$MB6.51536@fx33.am4> <ln5zv9m5zd.fsf@kst-u.example.com>
From Bart <bc@freeuk.com>
Message-ID <ddIWD.65091$8Q1.45353@fx14.am4> (permalink)
Organization virginmedia.com
Date 2019-01-01 11:32 +0000

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On 01/01/2019 03:06, Keith Thompson wrote:

> Bart <bc@freeuk.com> writes:

>>   From a design and implementation point of view, you have to go into it
>> in more detail.
> 
> No, you don't.  Any scalar expression can be compared for inequality
> to 0.  That's what if(), while(), et al are defined to do.
> (The comparison may involve a type conversion.)

It doesn't help when trying to implement if (A), when A represents any 
expression. Assuming A has a suitable scalar type, doing:

   if ((A)!=0)

might work, but is inappropriate when A is (a==b), or A is (a<b && c). 
(And in the latter, the argument applies to the 'c' operand of &&.)

>> Perhaps simpler might be to say that operands of if(), while(), for(;;),
>> &&, || unary !, need to be either already Bool, or have to be converted
>> to Bool.
> 
> Assuming you mean _Bool, no, that's not what they do.  C90 didn't
> have a boolean type.

I deliberately didn't use _Bool. None of my languages have a boolean 
type, but the compilers do have one internally, just for this purpose, 
as something that should be yield by a conditional expression.

>> It is that last that can also be done with !!.
> 
> No, !!expr (for any scalar expression expr) yields a value *of type
> int*, either 0 or 1.
> 
>      The result of the logical negation operator ! is 0 if the
>      value of its operand compares unequal to 0, 1 if the value
>      of its operand compares equal to 0. The result has type int.
>      The expression !E is equivalent to (0==E).

if X is a scalar expression, what's the difference in the value (not 
type) of !!X compared with (_Bool)X?

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Thread

Range-aware modulo operator -% "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-27 21:09 -0500
  Re: Range-aware modulo operator -% Richard Damon <Richard@Damon-Family.org> - 2018-12-27 21:34 -0500
    Re: Range-aware modulo operator -% "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2018-12-28 05:37 +0100
    Re: Range-aware modulo operator -% James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-29 16:04 -0500
      Re: Range-aware modulo operator -% Richard Damon <Richard@Damon-Family.org> - 2018-12-29 19:13 -0500
  Re: Range-aware modulo operator -% Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-28 03:05 +0000
    Re: Range-aware modulo operator -% Robert Wessel <robertwessel2@yahoo.com> - 2018-12-27 21:31 -0600
      Re: Range-aware modulo operator -% Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-28 04:20 +0000
    Re: Range-aware modulo operator -% James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-27 19:32 -0800
      Re: Range-aware modulo operator -% Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-28 04:18 +0000
  Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2018-12-28 12:29 +0000
    Re: Range-aware modulo operator -% "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-28 08:10 -0500
      Re: Range-aware modulo operator -% Richard Damon <Richard@Damon-Family.org> - 2018-12-28 10:25 -0500
        Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2018-12-28 15:56 +0000
          Re: Range-aware modulo operator -% Richard Damon <Richard@Damon-Family.org> - 2018-12-28 17:26 -0500
            Re: Range-aware modulo operator -% Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> - 2018-12-28 23:45 +0100
        Re: Range-aware modulo operator -% "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-28 11:44 -0500
        Re: Range-aware modulo operator -% "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-28 12:16 -0500
          Re: Range-aware modulo operator -% Richard Damon <Richard@Damon-Family.org> - 2018-12-28 17:08 -0500
            Re: Range-aware modulo operator -% Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-28 15:01 -0800
            Re: Range-aware modulo operator -% "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-31 09:04 -0500
              Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2018-12-31 18:07 +0000
                Re: Range-aware modulo operator -% "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-31 14:22 -0500
                Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2018-12-31 21:05 +0000
                Re: Range-aware modulo operator -% "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-31 16:32 -0500
                Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2018-12-31 23:43 +0000
                Re: Range-aware modulo operator -% Keith Thompson <kst-u@mib.org> - 2018-12-31 16:44 -0800
                Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2019-01-01 01:06 +0000
                Re: Range-aware modulo operator -% Keith Thompson <kst-u@mib.org> - 2018-12-31 19:06 -0800
                Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2019-01-01 11:32 +0000
                Re: Range-aware modulo operator -% Keith Thompson <kst-u@mib.org> - 2019-01-01 12:48 -0800
                Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2019-01-01 23:54 +0000
                Re: Range-aware modulo operator -% Keith Thompson <kst-u@mib.org> - 2019-01-01 16:09 -0800
                Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2019-01-02 00:49 +0000
                Re: Range-aware modulo operator -% Keith Thompson <kst-u@mib.org> - 2019-01-01 17:53 -0800
                Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2019-01-02 02:36 +0000
                Leader Kiki is not going to like this... (Was: Range-aware modulo operator -%) gazelle@shell.xmission.com (Kenny McCormack) - 2019-01-02 08:36 +0000
                Re: Range-aware modulo operator -% Keith Thompson <kst-u@mib.org> - 2019-01-02 00:38 -0800
                Re: Range-aware modulo operator -% rbowman <bowman@montana.com> - 2019-01-01 22:40 -0700
                Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2019-01-02 12:12 +0000
                Re: Range-aware modulo operator -% gazelle@shell.xmission.com (Kenny McCormack) - 2019-01-01 01:53 +0000
                Re: Range-aware modulo operator -% Richard Damon <Richard@Damon-Family.org> - 2018-12-31 16:57 -0500
                Re: Range-aware modulo operator -% Bart <bc@freeuk.com> - 2018-12-31 22:33 +0000
                Re: Range-aware modulo operator -% Keith Thompson <kst-u@mib.org> - 2018-12-31 13:34 -0800
                Re: Range-aware modulo operator -% Richard Damon <Richard@Damon-Family.org> - 2018-12-31 16:43 -0500
                Re: Range-aware modulo operator -% Keith Thompson <kst-u@mib.org> - 2018-12-31 15:20 -0800
  Re: Range-aware modulo operator -% Eduardo <abdulai60@gmail.com> - 2018-12-28 07:18 -0800
    Re: Range-aware modulo operator -% "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-28 11:45 -0500

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