class Complex {
  Double re
  Double im

 String toString() {
  re + ' + ' + im + 'i'
 }

 Complex plus(Complex c) {
  new Complex(re: this.re + c.re, im: this.im + c.im)
 }
}

def c1 = new Complex(re:2, im:3.5)
def c2 = new Complex(re:4.2, im:7.1)
println 'c1 : ' + c1
//c1 : 2.0 + 3.5i
println 'c2 : ' + c2
//c2 : 4.2 + 7.1i
def result = c1 + c2
println 'result : ' + result
//result : 6.2 + 10.6i

​