beats = (you, opponent)->
    if you is 'rock'
        if opponent is 'scissors'
            return true
        else
            return false 
    else if you is 'paper'
        if opponent is 'rock'
            return true
        else
            return false
    else if you is 'scissors'
        if opponent is 'paper'
            return true
        else
            return false
    else
        throw new Error("your hand is unexpected: #{you}")
    
you = 'rock'
opponent = 'paper'

console.log beats(you, opponent)
console.log beats(opponent, you)

class Rock
    beats: (hand)->
        return hand instanceof Scissors

class Paper
    beats: (hand)->
        return hand instanceof Rock

class Scissors
    beats: (hand)->
        return hand instanceof Paper


you = new Rock
opponent = new Paper

console.log you.beats(opponent)
console.log opponent.beats(you)

beats(rock, scissors).
beats(paper, rock).
beats(scissors, paper).