Lab 4.2: Rock, Paper, Scissors with Actions

Goals

The goals of this lab are to learn the following:

• How to implement actions without parameters and return types
• How to read and understand requirements to write basic actions

Computer Science Principles Curriculum

• Big Idea: Algorithms: EK 4.1.1A, EK 4.1.1B, EK 4.1.1C, EK 4.1.1D, EK 4.1.1E, EK 4.1.1F, EK 4.1.1G, EK 4.1.1H, EK 4.2.1A, EK 4.2.1B
• Big Idea: Programming: EK 5.1.2A, EK 5.1.2B, EK 5.2.1A, EK 5.2.1B, EK 5.2.1C, EK 5.2.1D, EK 5.2.1E, EK 5.5.1A, EK 5.5.1D

Overview

In this lab, you will be writing a Rock Paper Scissors game. In this game a human player will be competing with the computer. The human player will choose rock, paper, or scissors and then the computer will randomly select one of the options. Then your program will tell the player who won the round. The use of actions will allow you to organize the game and make the program look organized.

Task 2: Create A Game with Actions

You are going to create a game with actions. You will separate each action so that they serve their own purpose. The first of these actions will be the PlayersTurn action. This action should ask the user to choose rock, paper, or scissors and it should continue to ask the user this until a valid input is given.

Go to the PlayersTurn action. Within that action start writing code at the comment that says "your code goes here". You will need your code to do the following:

• Declare a boolean and initialize it to false to track valid input.
• Create a loop that loops until the input is valid.
• Within that loop, ask the user to choose rock, paper, or scissors.
• Cast the input from the user to an integer and store it in the choice variable(has already been declared in this action).
• Check if the input is valid; if it is valid the loop should stop.

The existing code then returns the user's choice from the action, return choice, is already written into the action. Don't worry about calling and testing this action right now. You will come back to this when you write the PlayGame action. Instead move onto writing the ComputersTurn action.

Go to the ComputersTurn action. Within that action start writing code at the comment that says "your code goes here". You will need your code to do the following:

• Declare a Random object. e.g. Random random.
• Generate a random integer between 1 and 3, including 1 and 3.
• Assign the random integer to the choice variable.

The computers choice is then returned(the code for this is already included).

The next action you are going to write is the DetermineWinner action. This action has two parameters: playerChoice and computerChoice. For this to be a general solution you won't worry about the value of each parameter; those are determined when you call the DetermineWinner action. In this action you want to use conditional statements to determine if there is a tie, if the computer won, or if the player won.

To start writing this action you can use the following code:

if playerChoice = computerChoice then
   say "It's a tie!"
end

Add onto this conditional so that, if:

• Player chooses rock and computer chooses paper the output is, "Paper beats rock - the computer wins!"
• Player chooses rock and computer chooses scissors the output is, "Rock beats scissors - you win!"
• Player chooses paper and computer chooses rock the output is, "Paper beats rock - you win!"
• Player chooses paper and computer chooses scissors the output is, "Scissors beats paper - the computer wins!"
• Player chooses scissors and computer chooses paper the output is, "Scissors beats paper - you win!"
• Player chooses scissors and computer chooses rock the output is, "Rock beat scissors - the computer wins!"

The next action you will write is the PlayGame action. This action handles all of the game play, including getting the player's choice, randomly generating the computer's choice, determining a winner of the round, and asking the player if they want to continue playing or stop the game.

In this action, start by defining a text variable called playAgain and initialize it to "Y". Create a loop that will continue to loop when playAgain is equal to "Y" or "y". Inside this loop you need to call the PlayersTurn action and store the returned value in a variable named player with a type of integer. Then do the same with the ComputersTurn action. Store the returned value in a variable named computer with a type of integer. Call DetermineWinner passing the arguments player and computer. Finally, ask the user, "Would you like to play again (Y/N)?", and assign the result to the playAgain variable.

When you are done the PlayGame action should look like the following code:

action PlayGame
    text playAgain = "Y"
    repeat while playAgain = "Y" or playAgain = "y"
        integer player = PlayersTurn()
        integer computer = ComputersTurn()
        DetermineWinner(player, computer)
        playAgain = input("Would you like to play again (Y/N)?")
    end
end

The final step is to finish writing the Main action. The Main action should give the instructions, play the game, and say "Game over" when the game is done.

Sample Output

The following is sample output from the game:

Welcome to the Rock Paper Scissors game!
Here are the rules:
The player and the computer will pick rock, paper, or scissors.
Paper beats rock.
Rock beats scissors.
Scissors beat paper.
Enter a 1 for rock, a 2 for paper, or a 3 for scissors.
Rock (1), Paper (2), or Scissors (3)? 
4
Error: The value needs to be between 1 and 3. Please try again. You entered 4
Rock (1), Paper (2), or Scissors (3)? 
1
Rock beats scissors - you win!
Would you like to play again (Y/N)? 
Y
Rock (1), Paper (2), or Scissors (3)? 
1
Paper beats rock - the computer wins!
Would you like to play again (Y/N)? 
y
Rock (1), Paper (2), or Scissors (3)? 
3
It's a tie!
Would you like to play again (Y/N)? 
N
Game over

Debug your program and fix any compiler errors there might be. Now would be a great time to use the debugger to test your program. When an action is called use 'step into' to see what happens when a particular action is called. Did your program run correctly? If not, fix any problems. Show the work to the instructor.

Next Tutorial

In the next tutorial, we will discuss 3D Drawing, which describes how to draw in 3D.