groovy-operators-overloading

Easy example of operators overloading in groovy.

Reference: http://groovy-lang.org/operators.html#Operator-Overloading
Reference: https://en.wikipedia.org/wiki/Complex_number

preface

Groovy allows you to overload the various operators so that they can be used with your own classes.

All (non-comparator) Groovy operators have a corresponding method that you can implement in your own classes. The only requirements are that your method is:

• public,
• has the correct name,
• and has the correct number of arguments. The argument types depend on what types you want to support on the right hand side of the operator.

Operator	Method	Operator	Method
+	a.plus(b)	a[b]	a.getAt(b)
-	a.minus(b)	a[b] = c	a.putAt(b, c)
*	a.multiply(b)	a in b	b.isCase(a)
/	a.div(b)	<<	a.leftShift(b)
%	a.mod(b)	>>	a.rightShift(b)
**	a.power(b)	>>>	a.rightShiftUnsigned(b)
|	a.or(b)	++	a.next()
&	a.and(b)	--	a.previous()
^	a.xor(b)	+a	a.positive()
as	a.asType(b)	-a	a.negative()
a()	a.call()	~a	a.bitwiseNegate()

project description

We provide ComplexNumber (equivalent to a point) class with overloaded operators:

• +

  ComplexNumber plus(ComplexNumber other) {
      new ComplexNumber(this.x + other.x, this.y + other.y)
  }
  

• -

  ComplexNumber minus(ComplexNumber other) {
      new ComplexNumber(this.x - other.x, this.y - other.y)
  }
  

• *

  ComplexNumber multiply(ComplexNumber other) {
      new ComplexNumber(this.x * other.x - this.y * other.y, this.x * other.y + this.y * other.x)
  }
  

• /

  ComplexNumber div(ComplexNumber other) {
      this * other.reciprocal()
  }
  

• a[b]

  double getAt(int idx) {
      if (idx == 0) x
      else if (idx == 1) y
      else throw new IllegalArgumentException("Wrong coordinate index, use 0 or 1")
  }
  

  • a[0] == x
  • a[1] == y
  • a[>1] -> IllegalArgumentException so you could decompose ComplexNumber to a point:

    given:
    def x = 1.55
    def y = -2.23
    ComplexNumber complexNumber = new ComplexNumber(x, y)
    
    when:
    def (xValue, yValue) = complexNumber
    
    then:
    xValue == 1.55
    yValue == -2.23
    

addition

It is very useful to decompose list after splitting:

given:
def list = 1..10

when:
def (less, more) = list.split { it < 5 }

then:
less == 1..<5
more == 5..10