// why is the numbers example a good demonstration of pattern matching?

interface Number {
    boolean equals(Number other);
}

class Integer implements Number {
    int x;
    Integer(int y) { x=y; }
    public String toString() { return ""+x; }
    public boolean equals(Number other) {
	return
	    switch (other) {
	    case Integer n -> x==n.x;
	    case Rational r -> x*r.d == r.n;
	    case Real r -> (double)x==r.r;
	    case Complex c -> c.i==0 && (double)x==c.r;
	    default -> false;
	    };
    }
}
class Rational implements Number {
    int n;
    int d;
    Rational(int a, int b) {n=a;d=b;}
    public String toString() { return n+"/"+d; }
    public boolean equals(Number other) {
	return switch (other) {
	case Rational R -> n*R.d == d*R.n;
	case Real R -> n==d*R.r;
	case Complex C -> C.i==0 && C.r*d==n;
	default -> other.equals(this);
	};
    }
}
class Real implements Number {
    double r;
    Real(double x) {r=x;}
    public String toString() { return ""+r; }
    public boolean equals(Number other) {
	if (other instanceof Real) {
	    return r==((Real)other).r;
	}
	else if (other instanceof Complex) {
	    return ((Complex)other).i==0 && ((Complex)other).r==r;
	}
	else return other.equals(this);
    }
}
class Complex implements Number {
    double r;
    double i;
    Complex(double a, double b) {r=a; i=b;}
    public String toString() { return r+"+"+i+"i"; }
    public boolean equals(Number other) {
	if (other instanceof Complex C) {
	    return r==C.r && i==C.i;
	}
	else return other.equals(this);
    }
}

public class numbersattempt {
    static boolean equals(Integer A, Integer B) {
	return A.x==B.x;
    }
    static boolean equals(Integer A, Rational R) {
	return A.x*R.d == R.n;
    }
    static boolean equals(Integer A, Real R) {
	return A.x==R.r;
    }
    static boolean equals(Integer A, Complex C) {
	return C.i==0 && A.x==C.r;
    }
    static boolean equals(Rational A, Rational B) {
	return A.n*B.d == A.d*B.n;
    }
    //
    static boolean equals(Number a, Number b) {
	return equals(b,a);
    }

    public static void main(String[] args) {
	Number[] N = { new Integer(2), new Rational(6,3), new Real(2.5)};
	//System.out.println( equals(N[0],N[1]) );
	System.out.println(N[2].equals(N[0]));
    }
}