Exercise 35: Branches and Functions

You have learned if-statements, functions, and arrays. Now it's time to bend your mind. Type this in, and see if you can figure out what it's doing.

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def gold_room
  puts "This room is full of gold.  How much do you take?"

  print "> "
  choice = $stdin.gets.chomp

  # this line has a bug, so fix it
  if choice.include?("0") || choice.include?("1")
    how_much = choice.to_i
  else
    dead("Man, learn to type a number.")
  end

  if how_much < 50
    puts "Nice, you're not greedy, you win!"
    exit(0)
  else
    dead("You greedy bastard!")
  end
end


def bear_room
  puts "There is a bear here."
  puts "The bear has a bunch of honey."
  puts "The fat bear is in front of another door."
  puts "How are you going to move the bear?"
  bear_moved = false

  while true
    print "> "
    choice = $stdin.gets.chomp

    if choice == "take honey"
      dead("The bear looks at you then slaps your face off.")
    elsif choice == "taunt bear" && !bear_moved
      puts "The bear has moved from the door. You can go through it now."
      bear_moved = true
    elsif choice == "taunt bear" && bear_moved
      dead("The bear gets pissed off and chews your leg off.")
    elsif choice == "open door" && bear_moved
      gold_room
    else
      puts "I got no idea what that means."
    end
  end
end


def cthulhu_room
  puts "Here you see the great evil Cthulhu."
  puts "He, it, whatever stares at you and you go insane."
  puts "Do you flee for your life or eat your head?"

  print "> "
  choice = $stdin.gets.chomp

  if choice.include? "flee"
    start
  elsif choice.include? "head"
    dead("Well that was tasty!")
  else
    cthulhu_room
  end
end


def dead(why)
  puts why, "Good job!"
  exit(0)
end

def start
  puts "You are in a dark room."
  puts "There is a door to your right and left."
  puts "Which one do you take?"

  print "> "
  choice = $stdin.gets.chomp

  if choice == "left"
    bear_room
  elsif choice == "right"
    cthulhu_room
  else
    dead("You stumble around the room until you starve.")
  end
end

start

What You Should See

Here's me playing the game:

$ ruby ex35.rb
You are in a dark room.
There is a door to your right and left.
Which one do you take?
> right
Here you see the great evil Cthulhu.
He, it, whatever stares at you and you go insane.
Do you flee for your life or eat your head?
> cry
Here you see the great evil Cthulhu.
He, it, whatever stares at you and you go insane.
Do you flee for your life or eat your head?
> flee
You are in a dark room.
There is a door to your right and left.
Which one do you take?
> left
There is a bear here.
The bear has a bunch of honey.
The fat bear is in front of another door.
How are you going to move the bear?
> take honey
The bear looks at you then slaps your face off.
Good job!

Study Drills

  1. Draw a map of the game and how you flow through it.
  2. Fix all of your mistakes, including spelling mistakes.
  3. Write comments for the functions you do not understand.
  4. Add more to the game. What can you do to both simplify and expand it?
  5. The gold_room has a weird way of getting you to type a number. What are all the bugs in this way of doing it? Can you make it better than what I've written? Look at how =~ works for clues.

Common Student Questions

Help! How does this program work!?
When you get stuck understanding a piece of code, simply write an English comment above every line explaining what that line does. Keep your comments short and similar to the code. Then either diagram how the code works or write a paragraph describing it. If you do that you'll get it.
Why did you write while true?
That makes an infinite loop.
What does exit(0) do?
On many operating systems a program can abort with exit(0), and the number passed in will indicate an error or not. If you do exit(1) then it will be an error, but exit(0) will be a good exit. The reason it's backward from normal boolean logic (with 0==false) is that you can use different numbers to indicate different error results. You can do exit(100) for a different error result than exit(2) or exit(1).

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