scala - 为什么变量 newP2Points 的计算方式与 newP1Points 不同？

Question

我试图理解这段代码背后的想法。该代码详细说明了网球模型以将各个点建模为集会。

一场网球比赛由多组比赛组成，每组比赛由多场比赛组成。第一个赢得两盘的玩家赢得比赛。第一个赢得六场比赛的球员赢得一盘。第一个得到四分的玩家赢得比赛，除非两个玩家都得到三分。在这种情况下，第一个领先对手两分的玩家获胜。

我了解 Figaro 的功能，但有些代码行令人困惑。

object TennisGame{
 def tennis( probP1ServeWin: Double, probP1Winner: Double, probP1Error: 
             Double,probP2ServeWin: Double, probP2Winner: Double, 
             probP2Error: Double): Element[Boolean] = {

  def rally(firstShot: Boolean, player1: Boolean): Element[Boolean] = {
     val pWinner = 
      if(firstShot && player1) probP1ServeWin //pWinner will be equal 
                                                //with probP1ServeWinif is 
                                                //the first shot for 
                                                //player1

      else if (firstShot && !player1) probP2ServeWin  
      else if (player1) probP1Winner 
      else probP2Winner
      val pError =if (player1) probP1Error else probP2Error
      val winner = Flip(pWinner)  //winner will be true with a 
                                   //probability equals with pWinner and 
                                  //false with a probability 1- pWinner

      val error = Flip(pError) 

         //With the probability = winner, Constant(player1) is chosen, 
        //producing  player1 with probability 1.0, while with probability
       //1 - winner, If(error, Constant(!player1), rally(false, !player1)) 
      //is chosen

  If(winner, Constant(player1), If(error, Constant(!player1),
  rally(false,!player1)))

    }


 def game(p1Serves: Boolean, p1Points: Element[Int], p2Points: 
          Element[Int]): Element[Boolean] = {

   val p1WinsPoint = rally(true, p1Serves)

    //Apply takes two arguments  p1WinsPoint and p1Points, the Apply’s 
   //function argument takes one Boolean and one integer named wins and 
   //points and calculate the score for player 1
   val newP1Points = Apply(p1WinsPoint, p1Points, (wins: Boolean, points: 
                           Int) => if(wins) points + 1 else points)
   val newP2Points = Apply(p1WinsPoint, p2Points, (wins: Boolean, points: 
                           Int) =>if(wins) points else points + 1)
   val p1WinsGame = Apply(newP1Points, newP2Points, (p1: Int, p2: Int) => 
                          p1 >= 4 && p1- p2 >=2)
   val p2WinsGame = Apply(newP2Points, newP1Points, (p2: Int, p1: Int) => 
                          p2 >= 4 && p2- p1 >=2)
   val gameOver = p1WinsGame || p2WinsGame

  If(gameOver, p1WinsGame, game(p1Serves, newP1Points, newP2Points))
 }

def play(p1Serves: Boolean, p1Sets: Element[Int], p2Sets: Element[Int], 
         p1Games: Element[Int], p2Games: Element[Int]):Element[Boolean] ={

 val p1WinsGame = game( p1Serves, Constant (0), Constant(0))
 val newP1Games = Apply(p1WinsGame, p1Games, p2Games, (wins: Boolean, 
                         p1:Int, p2: Int) =>                                
                         if(wins){
                                  if(p1 >= 5) 0 else p1 + 1 
                            }else
                            {
                                if(p2 >=5) 0 else p1
                            })
val newP2Games = Apply(p1WinsGame, p1Games, p2Games, (wins: Boolean, p1: 
                        Int, p2: Int) =>
                            if(wins){
                               if(p1 >= 5) 0 else p2
                            }else
                            {
                                if(p2 >=5) 0 else p2 + 1
                            })
val newP1Sets = Apply(p1WinsGame, p1Games, p1Sets, (wins: Boolean, games: 
                       Int, sets: Int) =>
                       if(wins && games == 5) sets + 1 else sets)

val newP2Sets = Apply(p1WinsGame, p2Games, p2Sets, (wins: Boolean, games: 
                      Int, sets: Int) =>
                     if(!wins && games == 5) sets + 1 else sets)

val matchOver = Apply(newP1Sets, newP2Sets, (p1: Int, p2: Int) => 
                     p1 >= 2 | p2 >= 2)
 If(matchOver, Apply(newP1Sets, (sets: Int) => sets >= 2), play(!p1Serves, 
    newP1Sets, newP2Sets,newP1Games, newP2Games))
   }   
   play(true, Constant(0), Constant(0), Constant(0), Constant(0)) 
 }

 def main(args: Array[String]){}
}

标签： scalaprobabilityfigaro-lang