exercise-creation.rst

Create an Exercise

Teachers can define their exercises by

1. chose/create a suitable World
2. and define the challenge for it.

Chose a World

In general, one can distinguish between

Solving a problem instance

If the world creation is not randomized, one might want to allow students to solve a specific problem. They look at the World and move Robo accordingly. Therefore, they do not rely on loops.

Solving a set of problems

If the world creation is or can be randomized, one might want to force students to solve a whole set of problems. For example, navigate Robo through a randomized maze (generated by complex_maze())

There are a lot of predefined worlds that can be the basis for the teacher's exercises. Use the following factory functions to make use of them. To do call

>>> import roboworld as rw >>> world = rw.factory_function(...) >>> ...

Beginners

These Worlds can be the basis for learning the concept of method calls and conditionals. If one uses fixed dimensions of the World, students can solve those puzzles without using loops.

roboworld.leaf_corridor

Example exercise: Move Robofrom left to right. You will encounter LEAFS (green) along the way. Pick up all the LEAFS!

Challenge: Students have to move Robo, test for LEAFS and pick them up.

roboworld.corridor

Example exercise: Move Robofrom left to right. You will encounter STONES (orange) along the way. Robo can only carry one STONE at a time.

Challenge: Students have to move Robo, test for STONES, pick them up and put them down again. Therefore, they also have to turn Robo multiple times.

roboworld.new_world

Example exercise: Move Robo (blue) to its goal (purple).

Challenge: Students have to move Robo. If the World is randomized (e.g., random goal position), students have to come up with a search strategy!

roboworld.tunnel

Example exercise: Move Robo (blue) to the tunnel exit (purple) (or entry) without using robo.is_at_goal().

Challenge: Students have to define the tunnel exit and entry (the wall on the left and right) and test for it while walking towards the WEST.

Intermediates

The next set of Worlds can be used to introduce loops.

roboworld.simple_slalom

Example exercise: Move Robo (blue) to its goal by passing all WALLS (dark grey) from NORTH to SOUTH or vice versa, i.e., walk a slalom!

Challenge: Students have to generate a slalom movement pattern using multiple left turns and move instructions.

roboworld.multi_slalom

Example exercise: Move Robo (blue) to its goal by passing all WALLS (dark grey) from NORTH to SOUTH or vice versa, i.e., walk a slalom!

Challenge: Students have to generate a slalom movement pattern using multiple left turns and move instructions.

roboworld.round_trip

Example exercise: Move Robo (blue) to its goal. Find and pick up all the LEAFS!

Challenge: Students have to generate round-trip movement patterns using multiple left turns and move instructions. They have to test for LEAFS and pick them up. They should abstract new instructions:

• move Robo through a right corner
• move Robo through a left corner

roboworld.maze

Example exercise: Move Robo (blue) to its goal.

Challenge: Students have to recognize that the required movement pattern is repetitive and use this to their advantage.

roboworld.leaf_cross

Example exercise: Move Robo (blue) to its goal. Invert all cells, i.e., if there is no LEAF at a cell, place one. If there is a LEAF at a cell, remove it!

Challenge: Students have to move Robo through the whole World, test for LEAFS, and invert the cells' state accordingly. If Robo is initialized with enough LEAFS, the exercise is easier because students do not have to worry about visiting too many EMPTY cells consecutively.

roboworld.pacman

Example exercise: Move Robo (blue) to its goal by following the path of LEAFS.

Challenge: Students have to move Robo in a zig-zag movement pattern while Robo sensors the LEAFS accordingly.

Experts

roboworld.complex_maze

Example exercise 1: Move Robo (blue) through a randomly generated maze to its goal (purple).

Example exercise 2: Let Robo (blue) compute the shortest path through the randomly generated maze to its goal (purple). After computation, move the Robo back to its starting position and walk directly to its goal using the computed shortest path.

Challenge 1: Students have to develop a dept-first search strategy.

Challenge 2: Students must develop a breath-first search strategy, a way to move 'backward' and repeat a specific walk.

Hint: The dept-first search can be used to develop a breath-first search strategy.

roboworld.game_of_life

Example exercise: Let Robo play Conway's Game of Life. Update all cells according to the rules by manipulating the World using Robo.

Challenge: Students have to understand the rules of Conway's Game of Life. They have to develop a strategy such that the parallel update character of the cells is not broken.

Hints: Robo has enough LEAFS. Put a LEAF on each cell. Robo can mark and unmark a cell, this might be useful.

roboworld.sorting

Example exercise: Let Robo sort the LEAF-rows of the World. The consecutive LEAFS of each row of the World represent a number. Bring these rows/numbers from bottom to top in ascending order.

Challenge: Students understand and implement some sorting algorithms (e.g., bubble sort ). They have to abstract Robo instructions in such a way that they can make use of their sorting algorithm.

Create Your Own World

The easiest way to construct a customized World is to use yet another factory function.

roboworld.str_to_world

The string representation text has to be a rectangular string, i.e., a multiline string for which each line has the same length. Furthermore, if there is no 'G' (for the goal position), it will be placed at a random EMPTY position. If there is no 'R', 'N', 'W', 'S' or 'E' the robot will be placed at the center of the World; this might be impossible thus causes an exception!

For example:

>>> import roboworld >>> text= """############ >>> #----LL----# >>> #----------# >>> #----R-----# >>> #-O--------#""" >>> >>> world = rw.str_to_world(text) >>> fig = world.show(scale=0.3) >>> fig.savefig('world-str-to-world.png')

gives us

Note that the image is mirrored because position (0, 0) is at the top left.

Define the Challenge

Above we already propose some challenges, but one is free to define a new one. Your challenges will likely depend on each other. For example, in one challenge, students might have to define a function to turn Robo by 180 degrees - a very useful abstraction. This function will certainly be very helpful in solving many other problems.

An example stream of challenges can be found here. The text is written in German.