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std::setprecision

STD：设定精度

Defined in header ​​
/*unspecified*/ setprecision( int n ​​

在表达式中使用时out << setprecision(n)或in >> setprecision(n)，设置precision流参数out或in准确地说n...

参数

n-new value for precision

返回值

返回未指定类型的对象，以便在str类型的输出流的名称。std::basic_ostream<CharT, Traits>或类型的输入流。std::basic_istream<CharT, Traits>，然后表达str << setprecision(n)或str >> setprecision(n)行为就像执行了以下代码：

str.precision(n

例

二次

#include <iostream>
#include <iomanip>
#include <cmath>
#include <limits>
int main()
{
    const long double pi = std::acos(-1.L
    std::cout << "default precision (6): " << pi << '\n'
              << "std::setprecision(10): " << std::setprecision(10) << pi << '\n'
              << "max precision:         "
              << std::setprecision(std::numeric_limits<long double>::digits10 + 1)
              << pi << '\n';
}

二次

产出：

二次

default precision (6): 3.14159
std::setprecision(10): 3.141592654
max precision:         3.141592653589793239

二次

另见

fixedscientifichexfloatdefaultfloat (C++11)(C++11)changes formatting used for floating-point I/O (function)
precisionmanages decimal precision of floating point operations (public member function of std::ios_base)

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