C++输入输出

#include <iostream>
#include <string>
#include <sstream>

std::string convertToString(double x)
{
    std::ostringstream o;
    if( o << x)
    {
        return o.str();
    }
    
    return "conversion error";
} 

double convertToDouble(const std::string &str)
{
    std::istringstream i(str);
    double x;
    if( i >> x)
    {
        return x;
    }
    
    return 0.0;
    
}

int main()
{
    char b[10];
    std::string a;
    sprintf(b, "%d", 1975);
    a = b;
    std::cout << a << std::endl;
    
    std::string cc = convertToString(1976);
    std::cout << cc << std::endl;
    
    std::string dd = "2016";
    
    int p = convertToDouble(dd) + 2;
    std::cout << p << std::endl;
    
    return 0;
}