Converting a string like "2.12e-6" to a double
Is there a built in function in c++ that can handle conve开发者_运维知识库rting a string like "2.12e-6" to a double?
strtod()
atof
should do the job. This how its input should look like:
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.
If you would rather use a c++ method (instead of a c function)
Use streams like all other types:
#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 of course has a convenient short cut boost::lexical_cast<double> Or it is trivial to write your own.
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