user-0 提问: C语言运算符的顺序的疑问？

回复:
user: user-1
content: 注意符号位！！

user: user-2
content: int是有符号的 右移要保证符号不变

user: user-3
content: 仅供参考： #include <stdio.h> unsigned short int ui;   signed short int si; int main() {     ui=(unsigned short int)0x8000u;     si=(  signed short int)0x8000;     printf("ui=%u\n",ui);     printf("si=%d\n",si);     ui=ui>>1;     si=si>>1;     printf("ui=%u\n",ui);     printf("si=%d\n",si);      printf("--------------\n");     ui=(unsigned short int)0x8000u;     si=(  signed short int)0x8000;     printf("ui=%u\n",ui);     printf("si=%d\n",si);     ui=((  signed short int)ui)>>1;     si=((unsigned short int)si)>>1;     printf("ui=%u\n",ui);     printf("si=%d\n",si);      return 0; } //ui=32768 //si=-32768 //ui=16384 //si=-16384 //-------------- //ui=32768 //si=-32768 //ui=49152 //si=16384

user: user-3
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-4
content: 引用 6 楼 xviphackl 的回复:恍然大悟    感谢 @zhangxiangDavaid 大大的解答 我是小鲜肉，不是大大。

user: user-0
content: 引用 5 楼 zhangxiangDavaid 的回复:[quote=引用 4 楼 xviphackl 的回复:] [quote=引用 3 楼 zhangxiangDavaid 的回复:] a=1; ~a=11111111 11111111 11111111 11111110 ~a>>2 11111111 11111111 11111111 11111111     //最左边两位用符号位填充 以上就是-1的补码  符文号为什么需要用两个1来填充？我知道符号位不是左边第一个 0 表示正数 1 表示负数？ [/quote] 本质上，用0或1填充都行。 那就是说，看编译器怎么处理 大多数编译器，是这么干的： 右移，用符号位填充 左移，用0填充[/quote]  恍然大悟    感谢 @zhangxiangDavaid 大大的解答

user: user-4
content: 引用 4 楼 xviphackl 的回复:[quote=引用 3 楼 zhangxiangDavaid 的回复:] a=1; ~a=11111111 11111111 11111111 11111110 ~a>>2 11111111 11111111 11111111 11111111     //最左边两位用符号位填充 以上就是-1的补码  符文号为什么需要用两个1来填充？我知道符号位不是左边第一个 0 表示正数 1 表示负数？ [/quote] 本质上，用0或1填充都行。 那就是说，看编译器怎么处理 大多数编译器，是这么干的： 右移，用符号位填充 左移，用0填充

user: user-0
content: 引用 3 楼 zhangxiangDavaid 的回复:a=1; ~a=11111111 11111111 11111111 11111110 ~a>>2 11111111 11111111 11111111 11111111     //最左边两位用符号位填充 以上就是-1的补码  符文号为什么需要用两个1来填充？我知道符号位不是左边第一个 0 表示正数 1 表示负数？

user: user-4
content: a=1; ~a=11111111 11111111 11111111 11111110 ~a>>2 11111111 11111111 11111111 11111111     //最左边两位用符号位填充 以上就是-1的补码