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    <p><code>if (0)</code> evaluates the predicate <code>0</code> as a binary value. Binary values in C use integers, where zero means false and non-zero means true. Therefore, 0 will always evaluate to false.</p> <p>For binary operators, being right- or left-associative determines the order that otherwise equally important operators will be processed. Consider the subtraction operator:</p> <pre><code>37 - 10 - 4 </code></pre> <p>Both <code>-</code> are equal precedence so which should we evaluate first? Well, <code>-</code> is left-associative so we do:</p> <pre><code>(37 - 10) - 4 ==&gt; (27) - 4 ==&gt; 23 </code></pre> <p>If the <code>-</code> operator were right-associative, we would do:</p> <pre><code>37 - (10 - 4) ==&gt; 37 - 6 ==&gt; 31 </code></pre> <p>Equality (<code>=</code>) is right-associative because we might chain equalities together. So, if we see</p> <pre><code>// a and b are initialized to 0 a = b = 45 </code></pre> <p>Both <code>=</code> are equal precedence so we evaluate right to left and do:</p> <pre><code>a = (b = 45) // b receives 45 a = 45 // a receives 45 </code></pre> <p>If we were to go left-right, we'd get an unexpected result:</p> <pre><code>(a = b) = 45 // a receives 0 b = 45 // b receives 45 </code></pre> <p>For unary operators, however, ordering can only matter when multiple unary operators affect the same value. For example, let's do:</p> <pre><code>char x = 0xFF bool y = !~x </code></pre> <p>These unary operators are right-associative, so we do:</p> <pre><code>!(~0xFF) ==&gt; !(0x0) ==&gt; true </code></pre> <p>In the example you showed, the negation operators affecting <code>A</code> and <code>E</code> didn't have "equal precedence" because they didn't have the same operand. So, associativity doesn't apply.</p>
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    1. POAssociativity and Precedence in C
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    1. USRobert Martin
    1. USRobert Martin
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    1. COAssociativity of NOT is given as right to left in http://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B#Operator_precedence. That means in case of two operators having the same precedence, the rightmost will be executed first...?
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    2. CO@user980411 yes but only if they are not seperated by operators of different precedence does associativity matter (I think). I don't know where the associativity of a unary operator could matter.
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      1. USSeth Carnegie
    3. CO@user980411 right-associative means the `not` operator associates with the item on its right. That's why we write `!false` instead of `false!`. It doesn't mean `!a + !b` must have the `b` evaluated before the `a`.
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