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Re: C precedence - relative comparisons before equality operators

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On 07/09/2021 15:27, John Bode wrote:
> On 9/5/21 3:19 PM, Kenny McCormack wrote:
>> In article <sh2vvh$oir$1@dont-email.me>,
>> James Harris  <james.harris.1@gmail.com> wrote:
>>> According to
>>>
>>>    https://en.cppreference.com/w/c/language/operator_precedence
>>>
>>> and other references C applies relative comparisons (<, <=, >=, >)
>>> before equality comparisons (==, !=) rather than giving them all the
>>> same priority.
>>>
>>> Anyone know why the precedences were designed that way?
>>>
>>> Are there certain idioms in which that arrangement is useful?
>>
>> I think it makes sense.  If I see:
>>
>>      if (a < b == c < d)
>>
>> I would expect it to mean:
>>
>>      if ((a < b) == (c < d))
>>
>> That's got to be more useful than:
>>
>>      if ((a < (b == c)) < d)
>>
> 
> That's exactly the example given in footnote 108 of N1570:
> 
>    108) Because of the precedences, a<b == c<d is 1 whenever a<b and c<d
>         have the same truth-value
> 
> It's the same rationale as expecting "a + b == c + d" to be parsed as
> "(a + b) == (c + d)".  You want to see if two relational expressions
> are equivalent, and the way to enable that without having to use
> explicit parentheses everywhere is to make == and != lower precedence
> than <, >, <=, and >=.

But has anyone ever seen that in real code? And if they have, why 
wouldn't they also, at some point, have seen:

   (a == b) == (c == d)

Without parentheses, that becomes ((a==b)==c)==d).

It seems like they desperately wanted to find any excuse for justifying 
an extra, gratuitous precedence level for everyone to remember, when 
dropping one level would probably have had a greater net benefit.

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C precedence - relative comparisons before equality operators James Harris <james.harris.1@gmail.com> - 2021-09-05 18:49 +0100
  Re: C precedence - relative comparisons before equality operators Siri Cruise <chine.bleu@yahoo.com> - 2021-09-05 13:11 -0700
  Re: C precedence - relative comparisons before equality operators Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-09-05 21:12 +0100
    Re: C precedence - relative comparisons before equality operators David Brown <david.brown@hesbynett.no> - 2021-09-06 09:09 +0200
  Re: C precedence - relative comparisons before equality operators gazelle@shell.xmission.com (Kenny McCormack) - 2021-09-05 20:19 +0000
    Re: C precedence - relative comparisons before equality operators Richard Damon <Richard@Damon-Family.org> - 2021-09-05 17:52 -0400
      Re: C precedence - relative comparisons before equality operators Bart <bc@freeuk.com> - 2021-09-06 00:09 +0100
        Re: C precedence - relative comparisons before equality operators David Brown <david.brown@hesbynett.no> - 2021-09-06 09:15 +0200
          Re: C precedence - relative comparisons before equality operators Bart <bc@freeuk.com> - 2021-09-06 11:10 +0100
            Re: C precedence - relative comparisons before equality operators David Brown <david.brown@hesbynett.no> - 2021-09-06 13:01 +0200
              Re: C precedence - relative comparisons before equality operators Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-09-06 04:20 -0700
    Re: C precedence - relative comparisons before equality operators John Bode <jfbode1029@gmail.com> - 2021-09-07 09:27 -0500
      Re: C precedence - relative comparisons before equality operators Bart <bc@freeuk.com> - 2021-09-08 00:20 +0100
        Re: C precedence - relative comparisons before equality operators John Bode <jfbode1029@gmail.com> - 2021-09-08 14:18 -0500
  Re: C precedence - relative comparisons before equality operators Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-09-06 02:01 +0100
    Re: C precedence - relative comparisons before equality operators James Harris <james.harris.1@gmail.com> - 2021-09-06 09:39 +0100
      Re: C precedence - relative comparisons before equality operators Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-09-06 10:46 +0100
        Re: C precedence - relative comparisons before equality operators Richard Damon <Richard@Damon-Family.org> - 2021-09-06 10:09 -0400
          Re: C precedence - relative comparisons before equality operators Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-09-06 16:05 +0100
  Re: C precedence - relative comparisons before equality operators James Harris <james.harris.1@gmail.com> - 2021-09-06 09:27 +0100
    Re: C precedence - relative comparisons before equality operators James Harris <james.harris.1@gmail.com> - 2021-09-06 12:18 +0100
      Re: C precedence - relative comparisons before equality operators David Brown <david.brown@hesbynett.no> - 2021-09-06 13:44 +0200
        Re: C precedence - relative comparisons before equality operators James Harris <james.harris.1@gmail.com> - 2021-09-06 13:38 +0100
          Re: C precedence - relative comparisons before equality operators David Brown <david.brown@hesbynett.no> - 2021-09-06 18:12 +0200
        Re: C precedence - relative comparisons before equality operators tth <tth@none.invalid> - 2021-09-06 18:20 +0200
          Re: C precedence - relative comparisons before equality operators David Brown <david.brown@hesbynett.no> - 2021-09-06 23:40 +0200
      Re: C precedence - relative comparisons before equality operators Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-06 17:20 -0700
    Re: C precedence - relative comparisons before equality operators Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-09-06 13:44 +0100
    Re: C precedence - relative comparisons before equality operators Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-06 17:23 -0700
  Re: C precedence - relative comparisons before equality operators James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-09-06 23:07 -0400

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