Operators in C and C++: Difference between revisions

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==Operator precedence==

During expression evaluation, the order in which sub-expressions are evaluated is determined by [[order of operations|precedence]] and [[operator associativity|associativity]]. An operator with higher precedence is evaluated before a operator of lower precedence and the operands of an operator are evaluated based on associativity. The following table describes the precedence and associativity of the C and C++ operators. Operators are shown in groups of equal precedence with groups ordered in descending precedence from top to bottom.

The following table lists the [[order of operations|precedence]] and [[operator associativity|associativity]] of all the operators in the [[C (programming language)|C]] and [[C++]] languages. Operators are listed top to bottom, in descending precedence. Descending precedence refers to the priority of the grouping of operators and operands. Considering an expression, an operator which is listed on some row will be grouped prior to any operator that is listed on a row further below it. Operators that are in the same cell (there may be several rows of operators listed in a cell) are grouped with the same precedence, in the given direction. An operator's precedence is unaffected by overloading.

The syntax of expressions in C and C++ is specified by a [[phrase structure grammar]].<ref>{{cite book | title = ISO/IEC 9899:201x Programming Languages - C | date = 19 December 2011 | publisher = open-std.org – The C Standards Committee | pages = 465}}</ref> The table given here has been inferred from the grammar.{{Citation needed| date = January 2009}} For the ISO C 1999 standard, section 6.5.6 note 71 states that the C grammar provided by the specification defines the precedence of the C operators, and also states that the operator precedence resulting from the grammar closely follows the specification's section ordering:

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A precedence table, while mostly adequate, cannot resolve a few details. In particular, note that the [[ternary operator]] allows any arbitrary expression as its middle operand, despite being listed as having higher precedence than the assignment and comma operators. Thus <code>a ? b, c : d</code> is interpreted as <code>a ? (b, c) : d</code>, and not as the meaningless <code>(a ? b), (c : d)</code>. So, the expression in the middle of the conditional operator (between <code>'''?'''</code> and <code>''':'''</code>) is parsed as if parenthesized. Also, note that the immediate, unparenthesized result of a C cast expression cannot be the operand of <code>sizeof</code>. Therefore, <code>sizeof (int) * x</code> is interpreted as <code>(sizeof(int)) * x</code> and not <code>sizeof ((int) * x)</code>.

Operator precedence is not affected by overloading.

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