/* counter automaton that accepts matching ()'s like ((()()) 

3 states: 0 is both start and accept state, state 2 is dead state.
In state 0, on seeing (, sets counter to 1 and transition to state 1, else
goto state 2.
State 1 increments counter on seeing (, decrements on seeing ), making
sure that counter doesn't become negative by transitioning back to 0
when counter is 1.

This machine should run with keeprunning and skipbadinput both set to true
*/
public class parensfsm extends FSM4<Character>
{
    protected String instring;  // input string
    protected int indx=0;   // indexes instring
    protected int cx = 0; // counter for automaton
    java.util.HashMap<Character,Integer> Hash; // for implementing getindex    
    public parensfsm(String x)
	{
	    instring = x;
	    numstates = 3;
	    maxinputs = 2;
	    cx = 0;
	    setTable();
	}
    protected Character nextInput()
    {
	if (indx<instring.length()) return instring.charAt(indx++);
	else return null;
    }
    protected int getindex(Character x) { return Hash.get(x); }
    protected boolean acceptState(int s) { return s==0; }
    protected void setTable()
    {   // set hashmap
	Hash = new java.util.HashMap<Character,Integer>();
	Hash.put('(',0);  Hash.put(')',1);
	// set transition table
	M = new action[numstates][maxinputs];
	M[0][0] = () -> { cx=1; return 1; };
	M[0][1] = () -> 2;  // 2 is dead state
	M[1][0] = () -> { cx++; return 1; };
	M[1][1] = () -> { // seen ')'
	    cx--;
	    if (cx==0) return 0;
	    else return 1; 
                        };
	M[2][0] = M[2][1] = () -> 2; // not needed with skipbadinput=true
    }//setStateTable

    public static void main(String[] av)
    {
	String x = av[0]; // command-line string
	parensfsm machine = new parensfsm(x);
	machine.trace = true;
	machine.keeprunning = true; // process entire input
	boolean r = machine.run();
	System.out.println(r);
    }
}
// run: java parensfsm "(()))"   (should reject)