Functions, Coordinates
& the Haunted Carnival

This year builds on your previous experience coding in Minecraft. To get back into the swing of it, open a Minecraft world and press C on your keyboard, then choose any tutorial.

Not sure where to start? Try one of these.

Today introduces a new coding term. We are not going near the full object-oriented meaning; at this stage all you need to know is that encapsulation is a way of grouping your program into sections.

Technically, encapsulation means the grouping of data (attributes and stored values) and methods (functions, or code that does something) into single units, sometimes called a class, while restricting direct access to some of the components.

Got that? Do not stress if you did not. The part to focus on is methods and functions.

Methods and functions let you create segments of code that each handle one specific task. The difference is only in naming: method is the term used in object-oriented coding, which we are not doing, and function is the more general term, which is what we will be creating.

Last year you wrote code that was very close to a function without calling it one. Does this look familiar?

Now look at what happens when we split it up. There are two clear chunks of code, or more accurately two functions, each handling one specific task. They sit in the program doing nothing at all until they are called into action by a function call.

Building it this way might look like extra work. The payoff is that you can now spawn chickens or bees with individual chat commands and create both creatures at once, just by adding a call to each function.

How to create a function

Four steps, in order.

Here is another example, but this time the main body of each function has been left out. Mimic this code, then add the instructions needed inside each one to:

• Place an individual block when the user types block in the chat window.
• Place a stack of 3 blocks when the user types stack. Complete this as three separate block-place commands, keeping the X and Z coordinates the same and increasing Y by 1 each time.

def place_a_block():
    # command — any line with a # is treated as a comment, not actual code
    # command — remove these lines and replace them with actual commands

def build_a_stack():
    # command
    # command

player.on_chat("block", place_a_block)
player.on_chat("stack", build_a_stack)

So far each function does exactly the same thing every time. A parameter changes that: it lets the user hand a value to the function as they call it, and the function uses that value to decide what to do.

Notice the extra variable in build_a_custom_stack. When the user types custom 5, the value 5 is stored in the height variable and passed into the function as part of the function call. That value then decides how many times the loop repeats. The higher the number typed into chat, the more times the loop runs. Handy.

def place_a_block():
    # This is a function that only places one block
    blocks.place(DIAMOND_BLOCK, pos(3, 2, 3))

def build_a_stack():
    # Another function that runs when a function call is made
    for i in range(4):
        blocks.place(REDSTONE_ORE, pos(5, i, 1))

def build_a_custom_stack(height):
    # This function also takes a number, called a parameter,
    # and uses it within the code inside the function
    for i in range(height):
        blocks.place(GREEN_CONCRETE, pos(1, i, 5))

player.on_chat("block", place_a_block)
player.on_chat("stack", build_a_stack)
player.on_chat("custom", build_a_custom_stack)

Finally, try adding this code.

Run it, then type chunk 3 5 and chunk 20 4 into the chat window. What does this code do?

Using the code samples above, create your own program built from functions and function calls. Pick one option. This runs for the rest of this lesson, homework, and next lesson.

Rubric