Exit in Karel

Here’s an idiomatic Karel code example demonstrating the concept of exiting a program:

// This program demonstrates how to exit Karel's execution

define turnAround() {
    turnLeft();
    turnLeft();
}

// Main program
begin
    // Move forward and place a beeper
    move();
    putBeeper();

    // Check if there's a wall ahead
    if (frontIsBlocked()) {
        // If blocked, turn around and exit
        turnAround();
        exit();  // Exit the program immediately
    }

    // This code will not be executed if exit() is called
    move();
    putBeeper();
end

This Karel program demonstrates the concept of exiting program execution early. Here’s how it works:

1. We define a turnAround() function that makes Karel turn 180 degrees.

2. In the main program, Karel first moves forward and places a beeper.

3. We then check if there’s a wall in front of Karel using frontIsBlocked().

4. If there is a wall, Karel turns around and then calls exit(). This immediately stops the program’s execution.

5. The last two commands (move() and putBeeper()) will only be executed if there wasn’t a wall in front of Karel.

The exit() command in Karel is similar to the os.Exit() function in the original example. When exit() is called, the program stops immediately, and any subsequent commands are not executed.

To run this Karel program:

1. Save the code in a file with a .k extension (e.g., exit_example.k).
2. Load the file into a Karel IDE or interpreter.
3. Set up a world with at least two spaces in front of Karel’s starting position.
4. Run the program and observe Karel’s behavior.

If there’s no wall two spaces ahead, Karel will move twice and place two beepers. If there’s a wall two spaces ahead, Karel will move once, place one beeper, turn around, and then the program will exit without placing the second beeper.

This example demonstrates how to use conditional logic and the exit() command to control program flow in Karel, allowing for early termination based on specific conditions in the world.