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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: Remembering C's operator precedence rules
Date: Sat, 09 Mar 2019 12:32:51 -0800
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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)

(Some languages do chain comparison operators, and some forbid
expressions that would be ambiguous.  C just sits back and lets you
shoot yourself in the foot.)

[...]

> So how do you either remember these, or work them out from first
> principles?  Do you have any handy mnemonics or idiomatic examples to
> share?

I usually have a copy of n1570.pdf open.  When necessary, look at the
table of contents and check the subsection names in section 6.5.

-- 
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 */