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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: question about linker
Date: Wed, 11 Dec 2024 21:35:27 -0800
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Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:
[...]
> For (yet another) example; my K&R shows a syntax for expressions like
>
>   expression := binary
>   binary := binary + binary
>   binary := binary * binary

That's odd.  Is that an exact quotation?

> An actual expression   x = 2 + 3 * 4   would be "ambiguous" (without
> precedence rules).
[...]

My copy of K&R 1st edition (1978) has, among other things:

    multiplicative-expression:
        expression * expression
        expression / expression
        expression % expression

    additive-expression:
        expression + expression
        expression - expression

That's ambiguous (presumably precedence is defined elsewhere).

The second edition has something similar to what's in the C standard:

    multiplicative-expression:
        cast-expression
        multiplicative-expression * cast-expression
        multiplicative-expression / cast-expression
        multiplicative-expression % cast-expression

    additive-expression:
        multiplicative-expression
        additive-expression + multiplicative-expression
        additive-expression - multiplicative-expression

Which means that the precedence is defined by the grammar -- but
it also means that categories like "multiplicative-expression"
and "additive-expression" are broader than one might naively
expect.  For example, 42 is both a multiplicative-expression and
an additive-expression, even though it contains no multiplicative
or additive operators.  (Solving both issues would have required
using even more convoluted names for the categories.)

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */