import Prelude;

rel[str, str] whatbeats = {<"Rock", "Scissors">, <"Scissors", "Paper">, <"Paper", "Rock">};

list[str] ComputerChoices = ["Rock", "Paper", "Scissors"];

str CheckWinner(a, b){
   if(b == getOneFrom(whatbeats[a]))
      return a;
   elseif(a == getOneFrom(whatbeats[b]))
      return b;
   else return "Nobody";
}

public str RPS(human){
   computer = getOneFrom(ComputerChoices);
   x = if(human == "Rock") "Paper"; elseif(human == "Paper") "Scissors"; else "Rock";
   ComputerChoices += x;
   return "Computer played <computer>. <CheckWinner(human, computer)> wins!";
}