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Re: C precedence - relative comparisons before equality operators

From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: C precedence - relative comparisons before equality operators
Date 2021-09-06 10:46 +0100
Organization A noiseless patient Spider
Message-ID <87k0jujatb.fsf@bsb.me.uk> (permalink)
References <sh2vvh$oir$1@dont-email.me> <precedence-20210905232846@ram.dialup.fu-berlin.de> <87y28ajz4o.fsf@bsb.me.uk> <sh4k4k$cd5$1@dont-email.me>

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James Harris <james.harris.1@gmail.com> writes:

> On 06/09/2021 02:01, Ben Bacarisse wrote:
>> ram@zedat.fu-berlin.de (Stefan Ram) writes:
>> 
>>> James Harris <james.harris.1@gmail.com> writes:
>>>> Anyone know why the precedences were designed that way?
>>>
>>>    The precedence of > < <= >= over == != was already
>>>    present in B.
>>
>> Ah.  But not in BCPL, so Thompson thought it worth splitting them.
>> Mind you, BCPL permits expressions  like a < b < c and a < b = 0 with
>> the usual "mathematical" meaning. 
>
> I guess that's the meaning of "The result of evaluating an extended
> relation is true if and only if all the individual relations are
> true." in
>
>   https://www.bell-labs.com/usr/dmr/www/bcpl.pdf

Later documents are much clearer on this point.  The above document is
a technical note and not really a user manual.

> That document also appears to back up what you say about relative
> precedences. It says "The relational operators are less binding than
> the arithmetic operators."
>
> And, subsequently, "the shift operators are less binding than the
> relations on the left and more binding on the right." - which means
> something or other...!

It was trendy to have asymmetric precedence at one time (exponentiation
was the most common example, I think), but that seems to have been
dropped in later manuals.

-- 
Ben.

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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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