Complex Number in Groovy

Here's a quick note of making Groovy to support complex numbers:

1. override number operations via metaclass:
Number.metaClass.plus = { n ->
  if(n instanceof Imaginary) {
    return new Complex(r:delegate, i:n.v)
  }
}

2. define class Complex to hold real, r, and imaginary, i, parts
class Complex {
  def r
  def i
  String toString() {
    "$r + ${i}i"
  }
}

3. create class Imaginary to be a wrapper class (I borrow this idea from Scala's implicit converter).
class Imaginary {
  def v
}

4. define i as a global closure. It would be in DefaultGroovyMethods, actually.
def i = { v ->
  new Imaginary(v:v)
}

Then when you write:
def b = 2 + i(2.4)
println b
println b.class

This prints "2 + 2.4i" and the type of b is class Complex.