/// A class for handling complex numbers in Blink.
class Complex(real: Int, im: Int) {
    func real(): Int = real

    func setReal(r: Int) = real = r

    func im(): Int = im

    func setIm(i: Int) = im = i

    // We are redefining the + operation for our Complex class.
    // Thanks to this function, we can evaluate expressions like
    // new Complex(1, 2) + new Complex(3, 4) in the interpreter.
    func +(that: Complex): Complex = new Complex(real + that.real(), im + that.im())

    // Redefines the - operation for Complex.
    func -(that: Complex): Complex = new Complex(real - that.real(), im - that.im())

    // Redefines the * operation for our Complex class.
    func *(that: Complex): Complex = new Complex(
            real * that.real() - im * that.im(),
            real * that.im() + im * that.real()
        )

    // Redefines the / operation for Complex.
    func /(that: Complex): Complex = {
        let den = that.real() * that.real() + that.im() * that.im() in {
            new Complex(
                (real * that.real() + im * that.im()) / den,
                (im * that.real() - real * that.im()) / den
            )
        }
    }

    // All classes in Blink automatically extends the Object class which
    // already redefine the == operator to implement object equality.
    // Here, we are overriding Object's == definition to customize how
    // Complex objects are tested for equality.
    override func ==(that: Object): Bool = {
        // The instanceOf() function checks if an object
        // is an instance of the specified type.
        if (!that.instanceOf("Complex"))
            false
        else {
            // The as keyword is used to cast an object of one type
            // to another type.
            let complex = that as Complex in {
                real == complex.real() && im == complex.im()
            }
        }
    }

    // Overrides Object's toString() method to customize how Complex objects
    // are converted to string and printed in the interpreter.
    override func toString(): String = {
        if (real == 0 && im == 0) "0"
        else {
            if (real == 0) im + "i"
            else {
                if (im == 0) real.toString()
                else real + (if (im < 0) " - " + (-im) else " + " + im) + "i"
            }
        }
    }
}