Teaching Karel the Robot new commands involves defining control structures and functions that can be reused throughout the program. Below are explanations and examples of how to implement each of the requested functionalities in Karel’s programming environment.
1. For Loop
A for loop allows Karel to repeat a set of instructions a specific number of times. In many Karel implementations, you might use a repeat structure, which works similarly to a for loop.
Example:
def pick_up_balls(n):
for i in range(n):
if front_is_clear():
move()
pick_beeper() # Karel picks up a beeper at the current position.
In this example, Karel will move forward and pick up a beeper a specified number of times (n).
2. While Loop
A while loop lets Karel repeat commands as long as a certain condition is true.
Example:
def move_and_pick_until_no_beepers():
while beepers_present():
pick_beeper() # Karel picks up beeper until there are none left.
if front_is_clear():
move()
Here, Karel will continue picking up beepers and moving forward until there are no beepers left in the current row.
3. Define a New Function
You can define new functions to encapsulate behaviors that Karel should execute. Functions are reusable and can simplify the main logic of the program.
Example:
def turn_around():
turn_left()
turn_left() # Karel turns around, making 180-degree turn
def reach_wall_and_pick():
while front_is_clear():
move()
pick_up_balls(5) # Karel will execute a previous function to pick up 5 beepers.
In this example, turn_around() is a new function created to simplify Karel's turning logic.
4. The Main Function
The main function serves as the entry point for your program. Here, you bring together the various functions you've defined to execute Karel’s tasks.
Example:
def main():
move()
turn_left()
reach_wall_and_pick() # Calls the previously defined function
turn_around()
move()
The main() function orchestrates Karel’s actions: it moves, turns, and calls the function to reach the wall and pick beepers.
Putting It All Together
Here’s how everything may look combined into one Karel program:
def pick_up_balls(n):
for i in range(n):
if front_is_clear():
move()
pick_beeper()
def move_and_pick_until_no_beepers():
while beepers_present():
pick_beeper()
if front_is_clear():
move()
def turn_around():
turn_left()
turn_left()
def reach_wall_and_pick():
while front_is_clear():
move()
pick_up_balls(5)
def main():
move()
turn_left()
reach_wall_and_pick()
turn_around()
move()
In this complete example, Karel uses functions, loops, and conditionals to navigate, collect items, and perform tasks effectively. Each part of the code builds upon the previous concepts, making it modular and easy to understand.