Ok, so I've been trying to finish this program, but when I do things a certain way, I go through an infinite loop in which I am not sure how to stop or keep it from happening. The object of the program is to convert feet/inches into centimeters, provide exceptions on the datatypes so that a not numeric number or a negative number can be entered, then keep asking the user to input datatypes until they choose the option to close the program.

My problem happens ONLY when I enter a negative number in the sequence BEFORE I enter a character exception, this is where is throws me in the loop. But I do not get thrown in the loop if I enter the character first and then the negative number and then the normal numbers to close.

Can anyone identify the problem here? I've been reading the chapter in this book and trying to understand the examples but I see no fault in their explaining and my coding in comparison. I am sure its a user error and I over looked something.

#include <iostream>

using namespace std;

int main()
    double feet = 0, inches = 0, centimeters;
    string input = "ERROR: Input stream in fail state";
    bool done = false;
            cout << "Use this program to convert Feet and Inches into Centimeters." << endl; //Heading to explain usefulness of the program
            cout << endl;

do //Does the following code until done = true when input is correct.
            cout << "Enter amount of feet: "; //Asks for input of feet
            cin >> feet; //User enters value to store in feet
            cout << "Enter amount of inches: "; //Asks for input of inches
            cin >> inches; //User enters value to store in inches
            cout << endl;
            cout << "Your current values are: " << feet << " feet, " << inches << " inches." << endl; //Outputs feet and inches
            cout << endl;
            //throws exceptions to be caught and errors to be found if any
            if(inches < 0)
                    throw inches;
            else if (feet < 0)
                    throw feet;
            else if (!cin)
                    throw input;
            //Calculation to convert Feet/Inches into Centimeters
            inches = inches * 2.54; //One inch equals 2.54 centimeters; Multiplies user input by centimeter value.
            feet = feet * 30.48; //One foot = 30.48 centimeters; Multiplies user input by centimeter value.
            centimeters = feet + inches; //Adds the centimeter values together and stores in centimeters
            cout << "Here is the conversion in centimeters: " << centimeters << " centimeters" << endl; //Output centimeters
            cout << endl;

            done = true;
    }//End try
    catch(double x)
              cout << "You have entered a negative number. ERROR: "<< x << endl;           
    }//End feet catch
    catch(string invalidInput)
              cout << invalidInput << endl;
    }//End string catch
}//End do

    return 0;
};//End Main
If you run the code, enter a negative in the first value and then a character, you will get thrown in the loop. If you run the character first and then the negative, no loop.. I'm so confused.