A little program I wrote for fun !

[manasij7479]

Hey (...)
I know it could be considered somewhat arrogant to do this, but I'm just asking for some helpful 'reviews' of the following short program.
The program takes a yes/no Question and gives a random answer to it, remaining grammatically correct.
It works as expected, but there could be 'bad' code within it...that's the reason.


The functions used are:
std::string auxiliary_p(std::string);
std::string find_pronoun(std::string);
bool answer(std::string);
std::string modify(bool,std::string,std::string);
bool quit_condition();

#include<iostream> 
#include "functions.h"
using namespace std;

int main()
 {
        string input,pronoun,auxiliary,output;
        bool yes_or_no;
        do
        {
            cout<<"Input: ";
            getline(cin,input);

            auxiliary=auxiliary_p(input);  //Gets the auxiliary verb

            pronoun=find_pronoun(input);  // Gets the pronoun

            if(auxiliary=="NULL"||pronoun=="NULL")
            {
                cout<<"Try Again ."<<endl;
                continue;
            }
            yes_or_no = answer(input);

            output=modify(yes_or_no,pronoun,auxiliary);  //Attaches n't and/or puts yes/no 

            cout<<"Output: "<<output<<endl;
        } while(quit_condition());


        return 0;
 }

The implementations(attached the file because it is about 80 lines) :
functions.cpp