Julia multiple dispatch example using Rock, Paper, Scissors!

rock-paper-scissors.jl

abstract type Janken end

struct Rock     <: Janken end
struct Paper    <: Janken end
struct Scissors <: Janken end

janken(j1::Janken, j2::Janken) = println("Same object means a tie :O!")

janken(r::Rock, p::Paper)    = println("Rock is wrapped by paper :(")
janken(r::Rock, s::Scissors) = println("Rock crushes scissors!!!")

janken(p::Paper, s::Scissors) = println("Paper is cut by scissors :(")
janken(p::Paper, r::Rock)     = println("Paper wraps rock!!!")

janken(s::Scissors, r::Rock)  = println("Scissors is crushed by rock :(")
janken(s::Scissors, p::Paper) = println("Scissors cuts paper!!!")

# Multiple dispatch at work!
janken(Rock(), Paper())
janken(Paper(), Rock())
janken(Scissors(), Paper())

# Cases implemented by generic function
janken(Rock(), Rock())
janken(Paper(), Paper())
janken(Scissors(), Scissors())