In Assignment 1, you write Python code that will be used by a game called "The Slide Game". You can complete the whole assignment with only the concepts from Weeks 1, 2, and 3 of the course. This handout explains the problem being solved, and the tasks to complete, for the assignment. Please read it carefully and in its entirety.
Goals of this assignment:
The main goal of this assignment is that students will use the Function Design Recipe to plan, document, implement, and test functions. This entails the following sub-goals:
Logistics:
The Slide Game is a two player game played on a two-dimensional game board. The game board has a number of rows and columns specified at the beginning of the game and starts off filled with black squares. The following image is an example of a game board with 4 rows and 5 columns:
NUM_MATCH
of their squares in a straight line wins the game. Here, NUM_MATCH
is a number like 3. The "straight line" can be a horizontal, vertical, or diagonal line of squares on the game board.
The "Slide Right" move allows a player to slide one of their squares onto the game board. The player must indicate which row they would like to slide their square onto. Because the size of the game board is fixed, the right-most square in the game board will "fall off" to make room for the player's own square.
The "Slide Left" move allows a player to slide one of their squares onto the game board. The player must indicate which row they would like to slide their square onto. Because the size of the game board is fixed, the left-most square in the game board will "fall off" to make room for the player's own square.
The objective of the game is to be the first player to connect NUM_MATCH
squares in a row either horizontally (or simply "across"), vertically (or simply "down"), or diagonally. Diagonal lines come in two orientations: downward to the right and downdward to the left. Assuming NUM_MATCH is 3, here are some examples of where squares should be placed in order to win the game:
In this assignment, you will be writing Python code for the Slide Game. Instead of using colourful pictures of squares on a game board (as we saw in the last section), in our Python code we will use text to represent the squares (i.e., Python's str
type). In the rest of this section, we provide some details to help you understand how to approach the code you need to write.
For this assignment, we are giving you some files to help you get started. Please download the Assignment 1 Files and extract the zip archive. In total, we have provided you with three Python files:
slide_functions.py
This is the file where you will write your solution. Your job is to complete the file by implementing all the required functions. See the What to do section for more details.
slide_game.py
This is the main program that we have implemented for you. You will not modify this file. But you can run this file to play The Slide Game. Note that this won't be possible until you have correctly completed the functions in slide_functions.py
.
a1_checker.py
This is a checker program that you should use to check your code. You will not modify this file. See below for more information about a1_checker.py
.
Constants are special variables whose values should not change once assigned -- you saw constants in
the Week 2 Prepare module. A different naming convention (uppercase pothole) is used for constants, so that
programmers know to not change their values. For example, in the starter code, the constant SQUARE_BLACK
is assigned the value '-'
at the beginning of the module and the value of SQUARE_BLACK
should never change in your code. When writing your code, if you need to use a
black square, you should use SQUARE_BLACK
. The same applies for the other constant values.
Using constants simplifies code modifications and improves readability and changeability. For example, if we later decide
to use a different character to represent a black square, we would only have to make a change in one place (the SQUARE_BLACK
assignment statement), rather than throughout the program. This also makes our code more readable — whether we use '-'
or any other
character to represent a black square, we write our code using the constant SQUARE_BLACK
so it is clear to the reader what we mean.
A game board can be thought of as a table with rows (see the constant NUM_ROW
) and columns (NUM_COL
).
The size of a game board does not change during the course of a game. For example, here is an empty game board with 4 rows and 5 columns:
1 2 3 4 5
1 - | - | - | - | -
2 - | - | - | - | -
3 - | - | - | - | -
4 - | - | - | - | -
A location in the game board can be described by indicating the row and then the column. For example, using the empty game board above, (1, 1) indicates the location at the top-left of the game board. And (4, 5) indicates the bottom-right of the game board.
We will use strings (i.e., the str type) to represent the squares on a game board. The black squares will be: '-'
(SQUARE_BLACK
).
The red squares will be: 'R'
(SQUARE_RED
). The yellow squares will be: 'Y'
(SQUARE_YELLOW
).
We have not yet studied how to store 2-dimensional information in Python programs, so we will need a different way to represent our game board.
The approach that we will take for this assignment is to store the rows one after another, starting with the first row. Using our empty
(all black squares) game board example, this is: '--------------------'
. Using a slightly more interesting example:
1 2 3 4 5
1 R | - | - | - | -
2 - | - | - | - | Y
3 R | - | - | - | -
4 Y | - | - | - | -
Would be represented as 'R--------YR----Y----'
.
We have used row and column indices to describe the position of each square in the grid representation of a game board.
But each character in a Python str
is in a position that is described by a single index. How is the Python program going
to translate between row and column indices and str indices? To answer this question, we will have to determine a formula!
Consider the following concrete example:
1 2 3 4 5
1 A | B | C | D | E
2 F | G | H | I | J
3 K | L | M | N | O
4 P | Q | R | S | T
Which, as a string, is: 'ABCDEFGHIJKLMNOPQRST'
. Let us use the table below to derive a
formula that calculates the index based on: the location (i.e., row and column) and game board size (i.e., NUM_ROW
and/or NUM_COL
).
location | index | character |
---|---|---|
(1, 1) | 0 | A |
(1, 2) | 1 | B |
(1, 3) | 2 | C |
(1, 4) | 3 | D |
(1, 5) | 4 | E |
(2, 1) | 5 | F |
(2, 2) | 6 | G |
(2, 3) | 7 | H |
(2, 4) | 8 | I |
(2, 5) | 9 | J |
(3, 1) | 10 | K |
(3, 2) | 11 | L |
(3, 3) | 12 | M |
(3, 4) | 13 | N |
(3, 5) | 14 | O |
(4, 1) | 15 | P |
(4, 2) | 16 | Q |
(4, 3) | 17 | R |
(4, 4) | 18 | S |
(4, 5) | 19 | T |
From the table above, we see that the character in the square with position (2,1) (i.e., the square at row 2 and column 1) has index 5. The other squares in that row have indices 6, 7, 8 and 9. We conclude that when moving one square across a row, the index increases by 1.
The squares in column 3 have indices 2, 7, 12 and 17. Moving one square down a column increases the index by 5, the number of columns of the game board. We conclude that when moving one square down a column, the index increases by the game board's number of columns.
Let us now introduce variables that will allow us to express the formula explicitly.
Let a variable named str_index
refer to the position of a square in the str
representation of a game board
with size NUM_ROW
rows and NUM_COL
columns. Let variables row
and col
refer to the position of the same square in
the grid representation of a game board. From what we have seen, we can conclude that str_index
depends on row
, col
,
and NUM_COL
. That is, the following formula will compute str_index
:
(row - 1) * NUM_COL + (col - 1)
The minus 1's are needed for the arithmetic to work out. This is because we chose to index our rows and columns starting at 1 (as a thought exercise, what would the formula be if we chose to index the rows and columns starting at 0?).
slide_functions.py
.slide_game.py
, a1_checker.py
, and pyta
.a1_checker.py
(see below).We have included the type contracts and a specification of every function below; please read through them carefully. We will be evaluating your docstrings in addition to your code; include two examples in your docstrings. You will need to paraphrase the specifications of the functions to get an appropriate docstring description. Make sure you review the CSC108 Python Style Guidelines for the rules on how to write a docstring description.
create_empty_board() -> str
Specification: This function has no parameters. This function returns a string for storing information about a
game board that has NUM_ROW
rows and NUM_COL
columns. Each character in the returned string is to have been set to the SQUARE_BLACK
character.
Notes:
is_board_full(str) -> bool
Specification: This function has one parameter that refers to a valid game board. This function
returns True
if and only if all of the squares in the game board are not black. That is, True
is returned if and only if
there are no SQUARE_BLACK
characters in the game board.
Notes:
between(str, int, int) -> bool
Specification: This function has three parameters. The first parameter refers to a str
value,
the second to the minimum value for a range of values, and the third to the maximum value for a range of values.
Assume that the str
value can be converted to an integer. Assume that the value of the second parameter is less than or
equal to the value of the third parameter. This function returns True
if and only if the converted integer value of the first
parameter is not less than the second parameter and not more than the third parameter. In other words, True
is returned if and only
if the first parameter is between the second and third parameters, or equal to one or both of them.
Notes:
calculate_str_index(int, int) -> int
Specification: This function has two parameters. The first and second parameters refer to the
row and column, respectively, of a location in a valid game board whose size is given by constants NUM_ROW
and NUM_COL
.
Assume that each parameter refers to a valid value. This function returns the index in the string representation of the game board
corresponding to the given row and column location.
Notes:
calculate_increment(str) -> int
Specification: This function has one parameter. The parameter refers to a string that describes
one of the four directions: down, across, down-right, or down-left. Assume that the str
value is one of:
DIR_DOWN
, DIR_ACROSS
, DIR_DOWN_RIGHT
, or DIR_DOWN_LEFT
. The game board size is given by the constants NUM_ROW
and
NUM_COL
. This function returns the difference between the str
indices of two adjacent squares on a line that goes
in the direction specified by the first parameter.
Notes:
get_row(int, str) -> str
Specification: This function takes two parameters. The first parameter is a row number
and the second parameter is the string representation of a game board. Assume that the row number and game
board are valid. The game board size is given by the constants NUM_ROW
and NUM_COL
. This function returns only the
characters in the game board found at the given row in the same left-to-right order as they appear in the row.
Notes:
calculate_increment
and calculate_str_index
functions to help.get_column(int, str) -> str
Specification: This function takes two parameters. The first parameter is a column
number and the second parameter is the string representation of a game board. Assume that the column
number and game board are valid. The game board size is given by the constants NUM_ROW
and NUM_COL
. This
function returns only the characters in the game board found at the given column in the same top-to-bottom
order as they appear in the column.
Notes:
calculate_increment
and calculate_str_index
functions to help.slide_right(str, int, str) -> str
Specification: This function takes three parameters. The first parameter is the square being added to the game board. The second parameter is a row number and the third parameter is the string representation of a game board. Assume that the square, row number, and game board are valid. This function returns a string that is like the original game board, except that:
Notes:
calculate_str_index
function to help.slide_left(str, int, str) -> str
Specification: This function takes three parameters. The first parameter is the square being added to the game board. The second parameter is a row and the third parameter is the string representation of a game board. Assume that the square, row number, and game board are valid. This function returns a string that is like the original game board, except that:
Notes:
calculate_str_index
function to help.a1_checker.py
a1_checker.py
) that tests two things:
W0613 (unused-argument) Number of occurrences: 4.
[Line 42] The parameter 'game_board' is unused. This may indicate you misspelled a parameter name in the function body. Otherwise, the parameter can be removed from the function without altering the program.
40
41
42 def is_board_full(game_board: str) -> bool:
43 """Return True if and only if the game_board is full.
44
Reading the example:
The error message tells you exactly which line in the slide_functions.py
file you should inspect.
In our example above, that is line 42. The error unused_argument
in this example means that your
function body is not using the parameter called game_board
.
======================================================================
FAIL: test_between (__main__.SanityTest)
Check the type contract of function between.
----------------------------------------------------------------------
Traceback (most recent call last):
File "x-wingide-python-shell://119623232/2", line 99, in test_between
File "x-wingide-python-shell://119623232/2", line 145, in _check
AssertionError: False is not true : between should return a bool, but instead it returned None.
Reading the example:
The error message tells you which function in slide_functions.py
you should inspect.
In our example above, that is the between
function. The error AssertionError
in this example
could have many different kinds of messages. If we read this message closely, we see that we are
not returning the correct type (other errors may have a different message). That is, our implementation
of between
is returning None
, but it should be returning a value with type bool
.
This section describes the aspects of your work that may be marked for A1.
Make sure that you follow Python style guidelines that we have introduced and the Python coding conventions that we have been using throughout the semester. Although we don't provide an exhaustive list of style rules, the checker tests for style are complete. So if your code passes the checker, then it will earn full marks for coding style with one exception: docstrings may be evaluated separately. Make sure you review the CSC108 Python Style Guidelines for the rules on how to write a docstring description.
For each occurrence of a PyTA error, one mark (out of 20) deduction will be applied. For example, if a C0301 (line-too-long) error occurs 3 times, then 3 marks will be deducted. All functions, including helper functions, should have complete docstrings including preconditions when you think they are necessary.
Your functions should perform as specified. Correctness, as measured by our tests, will count for the largest single portion of your marks. Once your assignment is submitted, we will run additional tests not provided in the checker. Passing the checker does not mean that your code will earn full marks for correctness.
No remark requests will be accepted for code that didn't run and thus failed all the tests. This means a simple syntax error could result in a grade of 0 on the assignment. Before the deadline, you are responsible for running your code and the checker program to identify and resolve any errors that will prevent our tests from running.
slide_functions.py
to Assignment 1 (i.e., a1) on MarkUs. Remember that spelling of filenames, including case, counts: your file must be named exactly as above.