Million data document access of course design

Other types are converted to string type ：

        string to_string (int val);
        string to_string (long val);
        string to_string (long long val);
        string to_string (unsigned val);
        string to_string (unsigned long val);
        string to_string (unsigned long long val);
        string to_string (float val);
        string to_string (double val);

        string to_string (long double val);

c_str() yes Borland Packaged String A function in class , It returns the first character address of the current string . When you need to open a file with a file name entered by the user , It can be written like this ：ifstream in(st.c_str())

Examples ：

#include <iostream>
#include <fstream>
using namespace std;

int main()
{
string  a="outputdsaftttt.txt";
    ofstream output( a.c_str(), ios::out);
    if( ! output )
    {
        cerr << "Open output file error!" << endl;
        exit( -1 );
    }
    output.close();
    return 0;
}