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Groups > comp.lang.c > #141854
| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Remembering C's operator precedence rules |
| Date | 2019-03-09 14:17 -0800 |
| Organization | None to speak of |
| Message-ID | <ln5zsrlmju.fsf@kst-u.example.com> (permalink) |
| References | <87lg1o9efx.fsf@bsb.me.uk> <lna7i3lrf0.fsf@kst-u.example.com> <87ftrvaglt.fsf@bsb.me.uk> |
Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> Keith Thompson <kst-u@mib.org> writes:
>> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>> [...]
>>> Within the big block of relational operators, another grouping that
>>> looks odd at first is that == and != have their own precedence level
>>> just below <, >, <= and >=. This is another case that it's probably
>>> wise to assume not everyone knows, but /you/ might remember it if you
>>> consider that == and != make sensible logical connectives, rather like
>>> && and ||. For example, to test if four variables are in order --
>>> either ascending or descending -- you can write
>>>
>>> a <= b == b <= c == c <= d
>>>
>>> Compare that with
>>>
>>> a <= b && b <= c && c <= d
>>>
>>> for a single order.
>>
>> I think you forgot about associativity.
>> x == y == z
>> means
>> (x == y) == z
>> not
>> (x == y) && (y == z)
>
> Thanks. I should have looked for a better example as this one gets
> messy when corrected. Do you know of an example that would motivate the
> otherwise rather surprising separation between relational an equality
> operators?
You could use the same method to determine whether 3 values are in
either ascending or descending order:
a <= b == b <= c
It just breaks down when you need more than one "==" operator.
(I'd parenthesize that myself.)
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Will write code for food.
void Void(void) { Void(); } /* The recursive call of the void */
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Remembering C's operator precedence rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-09 16:53 +0000
Re: Remembering C's operator precedence rules Richard Damon <Richard@Damon-Family.org> - 2019-03-09 15:21 -0500
Re: Remembering C's operator precedence rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-09 21:41 +0000
Re: Remembering C's operator precedence rules Keith Thompson <kst-u@mib.org> - 2019-03-09 12:32 -0800
Re: Remembering C's operator precedence rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-09 21:21 +0000
Re: Remembering C's operator precedence rules Richard Damon <Richard@Damon-Family.org> - 2019-03-09 16:42 -0500
Re: Remembering C's operator precedence rules "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-03-09 14:01 -0800
Re: Remembering C's operator precedence rules Keith Thompson <kst-u@mib.org> - 2019-03-09 14:17 -0800
Re: Remembering C's operator precedence rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-10 00:42 +0000
Re: Remembering C's operator precedence rules Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2019-03-09 13:54 -0700
Re: Remembering C's operator precedence rules Bart <bc@freeuk.com> - 2019-03-09 21:37 +0000
Re: Remembering C's operator precedence rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-09 22:01 +0000
Re: Remembering C's operator precedence rules Richard Damon <Richard@Damon-Family.org> - 2019-03-09 18:59 -0500
Re: Remembering C's operator precedence rules Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-03-13 09:26 -0700
Re: Remembering C's operator precedence rules Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-03-13 10:11 -0700
Re: Remembering C's operator precedence rules Bart <bc@freeuk.com> - 2019-03-13 17:40 +0000
Re: Remembering C's operator precedence rules Keith Thompson <kst-u@mib.org> - 2019-03-13 15:24 -0700
Re: Remembering C's operator precedence rules Bart <bc@freeuk.com> - 2019-03-13 23:43 +0000
Re: Remembering C's operator precedence rules Keith Thompson <kst-u@mib.org> - 2019-03-13 17:43 -0700
Re: Remembering C's operator precedence rules Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-03-18 08:53 -0700
Re: Remembering C's operator precedence rules Wouter Verhelst <w@uter.be> - 2019-03-13 22:24 +0200
Re: Remembering C's operator precedence rules Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-03-13 14:06 -0700
Re: Remembering C's operator precedence rules Ian Collins <ian-news@hotmail.com> - 2019-03-14 14:28 +1300
Re: Remembering C's operator precedence rules scott@slp53.sl.home (Scott Lurndal) - 2019-03-14 13:35 +0000
Re: Remembering C's operator precedence rules Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-03-14 06:55 -0700
Re: Remembering C's operator precedence rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-14 16:39 +0000
Re: Remembering C's operator precedence rules scott@slp53.sl.home (Scott Lurndal) - 2019-03-14 17:37 +0000
Re: Remembering C's operator precedence rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-14 20:42 +0000
Re: Remembering C's operator precedence rules Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-03-14 10:42 -0700
Re: Remembering C's operator precedence rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-14 23:08 +0000
Re: Remembering C's operator precedence rules Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-03-15 02:53 -0700
Re: Remembering C's operator precedence rules Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2019-03-15 17:52 -0600
Re: Remembering C's operator precedence rules Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-03-13 12:56 -0700
Re: Remembering C's operator precedence rules Jens Stuckelberger <Jens_Stuckelberger@nowhere.net> - 2019-03-13 20:14 +0000
Re: Remembering C's operator precedence rules fir <profesor.fir@gmail.com> - 2019-03-19 14:17 -0700
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