LinuxQuestions.org - cin and do while problems

This a code for a calculator I'm doing.

main.cpp

Code:

#include <string>

#include "Equation.h"

using namespace std;



int main()

{

        Equation a;

        string expresion;

        char option;

        

        do{

                cout<<"\tMathematic Expression Calculator" << endl;

                cout<<endl;;



                cout<<"\ta) Enter Expression" << endl;

                cout<<"\tb) Help" << endl;

                cout<<"\n\tc) EXIT" << endl;

                cout<<endl;

                cout<<"\tOption: ";

                cin>>option;

                

                switch(option) 

                {



                case 'a':

                        

                        system("cls");

                        cout<<"Enter the expression: ";

                        getline(cin,expresion);

                        a.set(expresion);

                        a.rpn();

                        system("pause");

                        system("cls");

                        break;



                

                case 'b':

                        

                        system("cls");

                        cout<<"This calculator calculates the result of an mathematic expression.";

                        cout<<"\nIt uses the methodology of postfix to help calculate this.";

                        cout<<"\nExample mathematic expression is 4+5*(7-5)"<<endl;

                        system("pause");

                        system("cls");

                        break;



                case 'c':

                        

                        system("cls");

                        cout<<"Have a nice day."<<endl;

                        break;



                default:

                        

                        system("cls");

                        cout<<"\n\tInvalid Option\n"<<endl;

                        break;



                }

        }while(option !='c');



        return 0;



}

The code works fine but the problem is that when i try to implement the do while loop as you can see and the user chooses a to enter a expression it just skips the getline completely. If I don't do the do while loop everything works great. What I'm doing wrong here? Thanks

I didn't include the Equation.cpp file because is a little to long and I know is working but if you needed let me know. Also I have tested this in MS Visual 2005 and MS Visual 2008.