Thread: getline won't work

Hello everyone.

I've just started learning from "Jumping into C++". Great book. Unfortunately, I've also encountered my first snag. Practice problem number 3 from chapter 4 tells me to make a small calculator that takes one of the four arithmetic operations and its two arguments as input and give the result as output. Here's what my newbie mind came up with:

Code:

#include <iostream>
#include <string>


using namespace std;


int main()
{
    int a;
    int b;
    string operation;
    cout<<"a= "<<endl;
    cin>>a;
    cout<<"b= "<<endl;
    cin>>b;
    cout<<"What operation would you like performed? (add, subtract, divide, multiply)"<<endl;
    getline(cin, operation, '\n');
    if(operation=="add")
    {
        cout<<"a+b="<<a+b;
    }
    else if(operation=="subtract")
    {
        cout<<"a-b="<<a-b;
    }
    else if(operation=="divide")
    {
        cout<<"a/b="<<a/b;
    }
    else if(operation=="multiply")
    {
        cout<<"a*b="<<a*b;
    }
    cin.ignore();
    cin.get();
}

The thing that I don't get is why doesn't the function "getline" work. It's worked in previous programs. The program seems to work if I simply replace getline with a simple "cin". I could easily use that as a cheap fix but I am interested in knowing why "getline" refuses to work anymore.

I hope someone can enlighten me on this.

Thanks.

Well, let's look at what the user types in. Suppose the user inputs 4, 7, and multiply. The input stream would then hold "4\n7\nmultiply" (where \n = "Enter" or "Return"). cin >> a grabs the 4. cin >> b skips the \n (because that's not a number) and then grabs the 7. getline then grabs up to the next \n............

(Generally, mixing >> and getline is a fool's game.)

Thanks for the help guys. Now that I understand the problem I think I'll stick with cin until I find a truly useful advantage of using getline.