//
// four bit adder - uses FullAdder
// test the case 5+3 with Cin 0 and 1
//

public class FourBitAdder {
    
    public static void main (String[] args) {
	
	static final boolean[] A={true,false,true,false}; // 5 in binary
	static final boolean[] B={true,true,false,false}; // 3 in binaryCin
	static final boolean[] Cin={false,true}; // two runs   
		
	FA4class FA4 = new FA4class();
	for (int i=0; i<2; i++) {
	    FA4.compute (A, B, Cin[i]);
	    System.out.println ("\n5+3 with carry-in " + Cin[i] + " is");
	    for (int i=0; i<4; i++) System.out.println ("\t" + FA4.Sum[i]);
	    System.out.println ("\t" + FA4.Cout);
	}
    }
	
    class FAclass {
	boolean Sum, Cout;
	
	void compute (boolean A, boolean B, boolean Cin) {
	    Sum =  (A ^ B) ^ Cin;
	    Cout = (A & B) | (A & Cin) | (B & Cin);
	}
    }
    
    class FA4class {
	boolean[] Sum = new boolean[4];
	boolean Cout;
	boolean[] InternalCarry = new boolean[5];
	FAclass[] FA = new FAclass[4];
	
	FA4class () {
	    for (int i=0; i<4; i++) FA[i] = new FAclass();
	}
	
	void compute (boolean[] A, boolean[] B, boolean Cin) {
	    
	    InternalCarry[0] = Cin;
	    for (int i=0; i<4; i++) {
		FA[i].compute (A[i], B[i], InternalCarry[i]);
		Sum[i] = FA[i].Sum;
		InternalCarry[i+1] = FA[i].Cout;
	    }
	    Cout = InternalCarry[4];
	}
    }
}