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Re: Application Exercises

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  Re: Application Exercises Mateusz Viste <mateusz@wont.tell> - 2019-04-06 18:22 +0000
    Re: Application Exercises donalhambra@gmail.com - 2019-04-06 12:07 -0700
    Re: Application Exercises Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-04-06 23:52 -0700

#142867 — Re: Application Exercises

On Sat, 06 Apr 2019 18:01:32 +0000, Stefan Ram wrote:
> |Write a function to detect whether two integral numbers are |equal
> without using any comparison operators.
> 
>   . As a hint he wrote: "Think of bit operators.".

/* returns 0 if a == b, non-zero otherwise */
int isnotequal(int a, int b) {
  return(a ^ b);
}

Mateusz

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#142871

On Saturday, April 6, 2019 at 2:22:27 PM UTC-4, Mateusz Viste wrote:
> On Sat, 06 Apr 2019 18:01:32 +0000, Stefan Ram wrote:
> > |Write a function to detect whether two integral numbers are |equal
> > without using any comparison operators.
> > 
> >   . As a hint he wrote: "Think of bit operators.".
> 
> /* returns 0 if a == b, non-zero otherwise */
> int isnotequal(int a, int b) {
>   return(a ^ b);
> }

With signed magnitude -1 ^ +1 gives "minus zero" even
though -1 != +1.

-Don

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#142880

ram@zedat.fu-berlin.de (Stefan Ram) writes:

> Mateusz Viste <mateusz@wont.tell> writes:
>
>> On Sat, 06 Apr 2019 18:01:32 +0000, Stefan Ram wrote:
>>
>>> |Write a function to detect whether two integral numbers are |equal
>>> without using any comparison operators.
>>> . As a hint he wrote:  "Think of bit operators.".
>>
>> /* returns 0 if a == b, non-zero otherwise */
>> int isnotequal(int a, int b) {
>>  return(a ^ b);
>> }
>
>   Yeah, but what about padding bits (N2310, 6.2.6.2p5)?

Padding bits do not participate in the computation of
the &, ^, and | operators.  Unless the result is a trap
representation corresponding to a negative zero, or
the (trap) distinguished representation for two's
complement, these operators work as expected and always
produce valid values.

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