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<h3 class="section">8.8 Operator Precedence</h3>
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<p><a name="index-operator-precedence-521"></a>
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<dfn>Operator precedence</dfn> determines how operators are grouped, when
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different operators appear close by in one expression. For example,
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‘<samp><span class="samp">*</span></samp>’ has higher precedence than ‘<samp><span class="samp">+</span></samp>’. Thus, the expression
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<code>a + b * c</code> means to multiply <code>b</code> and <code>c</code>, and then add
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<code>a</code> to the product (i.e., <code>a + (b * c)</code>).
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<p>You can overrule the precedence of the operators by using parentheses.
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You can think of the precedence rules as saying where the parentheses
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are assumed if you do not write parentheses yourself. In fact, it is
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wise to use parentheses whenever you have an unusual combination of
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operators, because other people who read the program may not remember
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what the precedence is in this case. You might forget as well, and then
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you too could make a mistake. Explicit parentheses will help prevent
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<p>When operators of equal precedence are used together, the leftmost
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operator groups first, except for the assignment and exponentiation
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operators, which group in the opposite order. Thus, the expression
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<code>a - b + c</code> groups as <code>(a - b) + c</code>, but the expression
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<code>a = b = c</code> groups as <code>a = (b = c)</code>.
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<p>The precedence of prefix unary operators is important when another
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operator follows the operand. For example, <code>-x^2</code> means
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<code>-(x^2)</code>, because ‘<samp><span class="samp">-</span></samp>’ has lower precedence than ‘<samp><span class="samp">^</span></samp>’.
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<p>Here is a table of the operators in Octave, in order of increasing
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<dt><code>statement separators</code><dd>‘<samp><span class="samp">;</span></samp>’, ‘<samp><span class="samp">,</span></samp>’.
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<br><dt><code>assignment</code><dd>‘<samp><span class="samp">=</span></samp>’, ‘<samp><span class="samp">+=</span></samp>’, ‘<samp><span class="samp">-=</span></samp>’, ‘<samp><span class="samp">*=</span></samp>’,‘<samp><span class="samp">/=</span></samp>’. This operator
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<br><dt><code>logical "or" and "and"</code><dd>‘<samp><span class="samp">||</span></samp>’, ‘<samp><span class="samp">&&</span></samp>’.
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<br><dt><code>element-wise "or" and "and"</code><dd>‘<samp><span class="samp">|</span></samp>’, ‘<samp><span class="samp">&</span></samp>’.
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<br><dt><code>relational</code><dd>‘<samp><span class="samp"><</span></samp>’, ‘<samp><span class="samp"><=</span></samp>’, ‘<samp><span class="samp">==</span></samp>’, ‘<samp><span class="samp">>=</span></samp>’, ‘<samp><span class="samp">></span></samp>’, ‘<samp><span class="samp">!=</span></samp>’,
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‘<samp><span class="samp">~=</span></samp>’, ‘<samp><span class="samp"><></span></samp>’.
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<br><dt><code>colon</code><dd>‘<samp><span class="samp">:</span></samp>’.
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<br><dt><code>add, subtract</code><dd>‘<samp><span class="samp">+</span></samp>’, ‘<samp><span class="samp">-</span></samp>’.
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<br><dt><code>multiply, divide</code><dd>‘<samp><span class="samp">*</span></samp>’, ‘<samp><span class="samp">/</span></samp>’, ‘<samp><span class="samp">\</span></samp>’, ‘<samp><span class="samp">.\</span></samp>’, ‘<samp><span class="samp">.*</span></samp>’, ‘<samp><span class="samp">./</span></samp>’.
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<br><dt><code>transpose</code><dd>‘<samp><span class="samp">'</span></samp>’, ‘<samp><span class="samp">.'</span></samp>’
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<br><dt><code>unary plus, minus, increment, decrement, and ``not''</code><dd>‘<samp><span class="samp">+</span></samp>’, ‘<samp><span class="samp">-</span></samp>’, ‘<samp><span class="samp">++</span></samp>’, ‘<samp><span class="samp">--</span></samp>’, ‘<samp><span class="samp">!</span></samp>’, ‘<samp><span class="samp">~</span></samp>’.
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<br><dt><code>exponentiation</code><dd>‘<samp><span class="samp">^</span></samp>’, ‘<samp><span class="samp">**</span></samp>’, ‘<samp><span class="samp">.^</span></samp>’, ‘<samp><span class="samp">.**</span></samp>’.
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