c语言中(double)clock()，（double）在这里是什么功能？

[jcyumeng]

（double）clock（）中，（double）在这里是起什么作用，这个属于c语言里的什么语法？

[zilaishuichina]

类型强制转换 clock返回的是一个整数，把它强制转换成浮点数

[自信男孩]

这个是属于强制类型转换，double类型是8字节，可以表示的值比clock（）原有产生的数据类型表示的范围更大。这样是属于强制提高clock()的返回值类型。防止数据溢出或者丢掉；

[paschen]

把函数返回值强制转换为double类型，clock函数返回值为clock_t类型

[mstlq]

强制类型转换，大约等于 详细可以参考http://zh.cppreference.com/w/c/language/cast

double k；
k  =  （double）clock（）；

相当于

double k;
clock_t c = clock();
k = (double) c;

[mstlq]

楼上的“大约等于”四个字是手抖打出的废话，可以无视

[赵4老师]

//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 |
//+------------------+-----------------------------------------+---------------+