Actually I use a template function to perform this task, which is a more useful way to write the function that originated this thread ( because this single function can convert a string to any type of number: int, float, double, long double ):
#include "stdafx.h"
#include <string>
#include <iostream>
#include <Windows.h>
#include <sstream>
#include <iomanip>
using namespace std;
template <typename T>
inline bool StrToNum(const std::string& sString, T &tX)
{
std::istringstream iStream(sString);
return (iStream >> tX) ? true : false;
}
void main()
{
string a="1.23456789";
double b;
bool done = StrToNum(a,b);
cout << a << endl;
cout << setprecision(10) << b << endl;
system ("pause");
}
setprecision(10) ( iomanip ) is required otherwise istringstream will hide some decimals