Lecture Notes: Functions in Karel

What is a Function?

• A function is a way to teach Karel a new word.
• It helps break down a program into smaller, more understandable parts.
• Using functions is key to good programming style.

Structure of a Function

• Syntax: function functionName() { /* code */ }
• The function name should describe what the function does.
  • Example: buildPyramid suggests the function will build a pyramid.
• The code (instructions) for the function is placed within curly braces.

Defining vs. Calling a Function

• Defining a Function:

  • Specify the instructions for a new action.
  • Example: To define turnAround, write:

    function turnAround() {
      turnLeft();
      turnLeft();
    }
    

• Calling a Function:

  • Initiates the action specified by the function.
  • Example: To call turnAround, write:

    turnAround();
    

Rules for Defining a Function

• Function names should:
  • Start with a letter.
  • Contain no spaces.
  • Clearly describe the function's action.
• The function body contains the code between {}.

Example: Writing a Simple Program

• Goal: Create a program where Karel moves forward one step and then turns around.
• Steps:
  1. Use the move command.
  2. Call the turnAround function.
• Code:

  move();
  turnAround();
  

  • If turnAround isn't defined, define it:

    function turnAround() {
      turnLeft();
      turnLeft();
    }
    

• Execution: Run the program to see Karel move and then turn around (turn left twice).

Benefits of Using Functions

• Provides clarity on what the program does.
• Turns complex sequences into understandable actions.
• Enhances readability and maintainability of the code.