user-0 提问: num<<4*i>>28运算结合性

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user: user-1
content: //C++ Operators //  Operators specify an evaluation to be performed on one of the following: //    One operand (unary operator) //    Two operands (binary operator) //    Three operands (ternary operator) //  The C++ language includes all C operators and adds several new operators. //  Table 1.1 lists the operators available in Microsoft C++. //  Operators follow a strict precedence which defines the evaluation order of //expressions containing these operators.  Operators associate with either the //expression on their left or the expression on their right;    this is called //“associativity.” Operators in the same group have equal precedence and are //evaluated left to right in an expression unless explicitly forced by a pair of //parentheses, ( ). //  Table 1.1 shows the precedence and associativity of C++ operators //  (from highest to lowest precedence). // //Table 1.1   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 | //| <<               | Left shift                              | Left to right | //| >>               | Right shift                             | Left to right | //| <                | Less than                               | Left to right | //| >                | Greater than                            | Left to right | //| <=               | Less than or equal to                   | 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 | //| <<=              | Left-shift 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 | //+------------------+-----------------------------------------+---------------+

user: user-2
content: 引用 3 楼 wangdahu888 的回复:相当于 (num<<(4*i))>>28  ++

user: user-1
content: //Operator Precedence and Associativity //The table below lists the C and C++ operators and their precedence and associativity values. //The highest precedence level is at the top of the table. // ------------------------------------------------------------------------------------------------- // | Symbol                                   | Name or Meaning                    | Associativity | // |                                          | Highest Precedence                 |               | // | ++                                       | Post-increment                     | Left to right | // | --                                       | Post-decrement                     |               | // | ( )                                      | Function call                      |               | // | [ ]                                      | Array element                      |               | // | ->                                       | Pointer to structure member        |               | // | .                                        | Structure or union member          |               | // | ++                                       | Pre-increment                      | Right to left | // | --                                       | Pre-decrement                      |               | // | !                                        | Logical NOT                        |               | // | ~                                        | Bitwise NOT                        |               | // | -                                        | Unary minus                        |               | // | +                                        | Unary plus                         |               | // | &                                        | Address                            |               | // | *                                        | Indirection                        |               | // | sizeof                                   | Size in bytes                      |               | // | new                                      | Allocate program memory            |               | // | delete                                   | Deallocate program memory          |               | // | (type)                                   | Type cast [for example, (float) i] |               | // | .*                                       | Pointer to member (objects)        | Left to right | // | ->*                                      | Pointer to member (pointers)       |               | // | *                                        | Multiply                           | Left to right | // | /                                        | Divide                             |               | // | %                                        | Remainder                          |               | // | +                                        | Add                                | Left to right | // | -                                        | Subtract                           |               | // | <<                                       | Left shift                         | Left to right | // | >>                                       | Right shift                        |               | // | <                                        | Less than                          | Left to right | // | <=                                       | Less than or equal to              |               | // | >                                        | Greater than                       |               | // | >=                                       | Greater than or equal to           |               | // | ==                                       | Equal                              | Left to right | // | !=                                       | Not equal                          |               | // | &                                        | 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 | // | ? :                                      | Conditional                        | Right to left | // | =                                        | Assignment                         | Right to left | // | *=, /=, %=, +=, -=, <<=, >>=, &=, ^=, |= | Compound assignment                |               | // | ,                                        | Comma                              | Left to right | // |                                          | Lowest Precedence                  |               | // -------------------------------------------------------------------------------------------------

user: user-3
content: 相当于 (num<<(4*i))>>28

user: user-3
content: * >>  <<的结合性都是从左向右的, 但*的优先级要高于<< >>

user: user-3
content: 相当于 num<<(4*i)>>28