C++ 右结合律与左结合律详解 |
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运算符的结合性是指相同优先级的运算符在同一个表达式中，且没有括号的时候，运算符和操作数的结合方式，通常有从左到右结合和从右到左结合两种方式。 举个例子，假设~是一个运算符，又有表达式a~b~c，如果~是左结合的，那么该表达式被解析为(a~b)~c，如果~是右结合的，那么该表达式将被解析为a~(b~c)。比如上表中三目运算符?:是从右向左结合的 那么下面的表达式a > b ? b > c ? 1 : 0 : 2将被解析为 a > b ? (b > c ? 1 : 0) : 2。 再看下运算符的优先级和结合律： [cpp] view plain copy // C++ Operator Precedence and Associativity // The highest precedence level is at the top of the table. //+------------------+-----------------------------------------+---------------+ //| Operator | Name or Meaning | Associativity | //+------------------+-----------------------------------------+---------------+ //| :: | Scope resolution | None | //| :: | Global | None | //| [ ] | Array subscript | Left to right | //| ( ) | Function call | Left to right | //| ( ) | Conversion | None | //| . | Member selection (object) | Left to right | //| -> | Member selection (pointer) | Left to right | //| ++ | Postfix increment | None | //| -- | Postfix decrement | None | //| new | Allocate object | None | //| delete | Deallocate object | None | //| delete[ ] | Deallocate object | None | //| ++ | Prefix increment | None | //| -- | Prefix decrement | None | //| * | Dereference | None | //| & | Address-of | None | //| + | Unary plus | None | //| - | Arithmetic negation (unary) | None | //| ! | Logical NOT | None | //| ~ | Bitwise complement | None | //| sizeof | Size of object | None | //| sizeof ( ) | Size of type | None | //| typeid( ) | type name | None | //| (type) | Type cast (conversion) | Right to left | //| const_cast | Type cast (conversion) | None | //| dynamic_cast | Type cast (conversion) | None | //| reinterpret_cast | Type cast (conversion) | None | //| static_cast | Type cast (conversion) | None | //| .* | Apply pointer to class member (objects) | Left to right | //| ->* | Dereference pointer to class member | Left to right | //| * | Multiplication | Left to right | //| / | Division | Left to right | //| % | Remainder (modulus) | Left to right | //| + | Addition | Left to right | //| - | Subtraction | Left to right | //| | Right shift | Left to right | //| | Greater than | Left to right | //| = | Greater than or equal to | Left to right | //| == | Equality | Left to right | //| != | Inequality | Left to right | //| & | Bitwise AND | Left to right | //| ^ | Bitwise exclusive OR | Left to right | //| | | Bitwise OR | Left to right | //| && | Logical AND | Left to right | //| || | Logical OR | Left to right | //| e1?e2:e3 | Conditional | Right to left | //| = | Assignment | Right to left | //| *= | Multiplication assignment | Right to left | //| /= | Division assignment | Right to left | //| %= | Modulus assignment | Right to left | //| += | Addition assignment | Right to left | //| -= | Subtraction assignment | Right to left | //| = | Right-shift assignment | Right to left | //| &= | Bitwise AND assignment | Right to left | //| |= | Bitwise inclusive OR assignment | Right to left | //| ^= | Bitwise exclusive OR assignment | Right to left | //| , | Comma | Left to right | //+------------------+-----------------------------------------+---------------+有个需要注意的地方：数组解析和解引用与递增运算符混用 [cpp] view plain copy /*************************************************************************** * @file main.cpp * @author MISAYAONE * @date 17 March 2017 * @remark 17 March 2017 ***************************************************************************/ #include #include #include #include using namespace std; int main(int argc,char** argv) { //*(解引用)运算符优先级优于+(加号)运算符 int a[3][3] = {1,3,5,7,9,11,13,15,17}; cout |
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