C++ 转换浮点值时设置 std::to_string 的精度

Set precision of std::to_string when converting floating point values

提问by learnvst

In C++11, std::to_stringdefaults to 6 decimal places when given an input value of type floator double. What is the recommended, or most elegant, method for changing this precision?

在 C++11 中，当给定类型为or的输入值时， std:: to_string默认为 6 个小数位。更改此精度的推荐或最优雅的方法是什么？floatdouble

回答by hmjd

There is no way to change the precision via to_string()but the setprecisionIO manipulator could be used instead:

无法通过以下方式更改精度，to_string()但setprecision可以使用 IO 操纵器：

#include <sstream>

template <typename T>
std::string to_string_with_precision(const T a_value, const int n = 6)
{
    std::ostringstream out;
    out.precision(n);
    out << std::fixed << a_value;
    return out.str();
}