Rock-paper-scissors: Difference between revisions

=={{header|Scala}}==

You can invoke this game with an arbitrary number of weapons:

<lang Scala>object RockPaperScissors extends App {

import scala.collection.mutable.LinkedHashMap

def play(beats: LinkedHashMap[Symbol,Set[Symbol]], played: scala.collection.Map[Symbol,Int]) {

val h = readLine(s"""Your move (${beats.keys mkString ", "}): """) match {

case null => println; return

case "" => return

case s => Symbol(s)

}

beats get h match {

case Some(losers) =>

def weighted(todo: Iterator[(Symbol,Int)], rand: Int, accum: Int = 0): Symbol = todo.next match {

case (s, i) if rand <= (accum + i) => s

case (_, i) => weighted(todo, rand, accum + i)

}

val c = weighted(played.toIterator, 1 + scala.util.Random.nextInt(played.values.sum)) match {

// choose an opponent that would beat the player's anticipated move

case h => beats.find{case (s, l) => l contains h}.getOrElse(beats.head)._1

}

print(s" My move: $c\n ")

c match {

case c if losers contains c => println("You won")

case c if beats(c) contains h => println("You lost")

case _ => println("We drew") // or underspecified

}

case x => println(" Unknown weapon, try again.")

}

play(beats, played get h match {

case None => played

case Some(count) => played.updated(h, count + 1)

})

}

def play(beats: LinkedHashMap[Symbol,Set[Symbol]]): Unit =

play(beats, beats.mapValues(_ => 1)) // init with uniform probabilities

play(LinkedHashMap(

'rock -> Set('lizard, 'scissors),

'paper -> Set('rock, 'spock),

'scissors -> Set('paper, 'lizard),

'lizard -> Set('spock, 'paper),

'spock -> Set('scissors, 'rock)

))

}</lang>

{{out}}

<pre>Your move ('rock, 'paper, 'scissors, 'lizard, 'spock): paper

My move: 'paper

We drew

Your move ('rock, 'paper, 'scissors, 'lizard, 'spock): scissors

My move: 'paper

You won

Your move ('rock, 'paper, 'scissors, 'lizard, 'spock): rock

My move: 'scissors

You won

Your move ('rock, 'paper, 'scissors, 'lizard, 'spock): rock

My move: 'rock

We drew

Your move ('rock, 'paper, 'scissors, 'lizard, 'spock): rock

My move: 'paper

You lost

Your move ('rock, 'paper, 'scissors, 'lizard, 'spock): rock

My move: 'rock

We drew

Your move ('rock, 'paper, 'scissors, 'lizard, 'spock): rock

My move: 'paper

You lost

Your move ('rock, 'paper, 'scissors, 'lizard, 'spock): rock

My move: 'paper

You lost</pre>