c++ - 将像“2.12e-6”这样的字符串转换为双精度

Question

c++ 中是否有一个内置函数可以处理将“2.12e-6”之类的字符串转换为双精度字符串？

Answer 1

strtod()

Answer 2

atof应该做的工作。它的输入应该是这样的：

A valid floating point number for atof is formed by a succession of:

An optional plus or minus sign 
A sequence of digits, optionally containing a decimal-point character 
An optional exponent part, which itself consists on an 'e' or 'E' character followed by an optional sign and a sequence of digits. 

Answer 3

如果您更愿意使用 c++ 方法（而不是 ac 函数），
请像所有其他类型一样使用流：

#include <iostream>
#include <sstream>
#include <string>
#include <iterator>
#include <boost/lexical_cast.hpp>

int main()
{
    std::string     val = "2.12e-6";
    double          x;

    // convert a string into a double
    std::stringstream sval(val);
    sval >> x;

    // Print the value just to make sure:
    std::cout << x << "\n";

    double y = boost::lexical_cast<double>(val);
    std::cout << y << "\n";
}

boost 当然有一个方便的捷径 boost::lexical_cast<double> 或者自己编写也很简单。