// Student: Raichel Link
// Teacher: Ms. Ames
// Class: CS 311
//
// Recursion Example
// Finding WFFs

#include <iostream>
using namespace std;

//-----------------------------------------------------------------------------
// WFFCatcher identifies if a string fits the requirements to be a WFF.
// Then, it prints the results to the screen.
//-----------------------------------------------------------------------------

bool WFF()
{
    bool n;
    char ch;
   
    cin.get(ch);
    
    if(ch == 'p' || ch == 'q' || ch =='r' || ch == 's')
    {
        return true;
    }
	
    else if(ch == 'N')
    {
	return WFF();
    }

    else if(ch == 'C' || ch == 'A' || ch  == 'K' || ch == 'E')
    {
	return WFF() && WFF();
    }
    
    else
	return false;

}

int main ()
{
    bool m, u;
    char ch;

    cout << "Enter a string to be tested for WFF (terminated by end-of-line) : ";

    m = WFF();

    if(m == true)
    {
	cin.get(ch);
	if(ch == '\n')
	    cout << "\nYour string is a WFF.\n\n";
	else
	    cout << "\nYour string is not a WFF.\n\n";
    }
    else
	cout << "\nYour string is not a WFF.\n\n";

    return 0;
}