Question

I’m writing a very simple program where I want to get user input from the standard input stream (keyboard) and then do something based on what input I encountered. However, the problem is that sometimes the input will be a number (double) while othertimes it’ll be a string. I’m not sure exactly what methods calls I need in order to parse it properly (perhaps something similar to Integer.parseInt in java).

Here is some pseduocode of what I would like to do:

cin >> input
if(input is equal to "p") call methodA;
else if(input is a number) call methodB;
else call methodC;

Answer 1

I think this is what you need:

#include <iostream>
#include <sstream>
#include <string>
using namespace std;

void a(string& s){ cout << "A " << s << endl; }
void b(double d){ cout << "B " << d << endl; }
void c(string& s){ cout << "C " << s << endl; }

int main()
{
    std::string input;
    cin >> input;
    if (input == "p")
        a(input);
    else
    {
        istringstream is;
        is.str(input);
        double d = 0;
        is >> d;
        if (d != 0)
            b(d);
        else
            c(input);
    }
    return 0;
}

Hope this helps 😉