Lab 03: Arrays and Swap

CS 2261 Lab 03:
Arrays and Swap
Provided Files
 main.c
 myLib.c
 myLib.h
 coords.c
 coords.h
Files to Edit/Add
 main.c
 Your Makefile
Instructions
In this lab, you will be completing several different TODOs, which will, piece by piece,
complete a simple cactus jumping game (although the term “game” only loosely applies
to this one). Your code may not compile until you complete an entire TODO block, at
which point the game should compile with a new component of the final outcome
(unless otherwise specified).
 TODO 1 – Cacti
 First, we want to create the cacti. They will sit on the top of the sand, and
will move to the write (the movement has already been written).
o TODO 1.0: Find the cactusCols and oldCactusCols arrays in
main.c. These will be the locations of the cacti. Notice that we don’t have
variables for the lengths of these, so we’re going to find a way to calculate
the length when we need it.
o TODO 1.1: Find the drawCacti function. Complete this by calling the
already-written eraseCactus function with each column in your
oldCactusCols array (to erase them) and the drawCactus function for
each column in your cactusCols array (to draw them).
 Hint: you will need to calculate (not hard code) the length of the
arrays. Since they are preallocated globally, what tool can we use
to find the length?
o TODO 1.2: Call the drawCacti function in the main while loop to draw
your cacti each frame of the game.
 Compile and run. If you did everything correctly, you should see two
equally-spaced cacti moving to the right, and, when they hit the right side
of the screen, reset to the left.
 TODO 2 – Player
 The game wouldn’t be much fun without a player, so let’s draw one.
o TODO 2.0: Open coords.c and examine the contents. For this lab (and
this lab only), we have opted to draw the player by having arrays of
coordinates (row arrays that match up to column arrays), and setting a
pixel at each of those row-column pairs. Note that there is a macro
defining the length of the coordinate arrays, which we may need later.
o TODO 2.1: In main.c, find the drawPerson function. It takes an array of
rows and a same-length array of columns, along with the length of those
arrays (remember: there would otherwise be no way to determine this), as
well as a color. Complete this function so that it sets a pixel at each
corresponding row-column pair in the arrays to the specified color.
 Hint: don’t overthink this. All you’re doing is iterating over the length
of the arrays and calling setPixel for each i.
o TODO 2.2: In the main while loop, after waitForVBlank, call
drawPerson with the invisiblePerson arrays using the SKYCOLOR to
erase the person’s previous location (this will make sense later).
o TODO 2.3: A few lines later, call drawPerson with the visiblePerson
arrays using WHITE to draw the person’s current location.
 Compile and run. You should see our new player character on top of the
sand, getting repeatedly smacked by cacti.
 TODO 3 – Swap
 For the purposes of this lab, we’re going to have our player jump by
swapping the coordinates of the visiblePerson with those of the
invisiblePerson (who is currently safely above the cacti).
o TODO 3.0: In main.c, write a new function called swap that returns
void and swaps the value of two integers passed in as parameters. Don’t
forget to write a prototype at the top of main.c.
 Note: this function may NOT exploit the fact that the things we will
be swapping (in later TODOs) are statically allocated and/or in
arrays. It must work for any two integers.
 Hint: think about what you will need to actually take in as
arguments to make this work
o TODO 3.1: In our main while loop, if the Start button is pressed, utilize
your new swap function so that each element of invisiblePersonRows
is swapped with each corresponding element of visiblePersonRows,
and then the same for invisiblePersonCols and
visiblePersonCols.
 Compile and run. If everything is working right, every time you press the
Start button, the player character alternates between a place of safety
above the cacti and back to where they started, standing on the sand.
 TODO 4 – More Cacti
 Now that everything is working, let’s make it more exciting by adding more
cacti.
o TODO 4.0: Change the initialization of the cactusCols and the
oldCactusCols arrays so that the starting locations are 0, 73, and 147.
 Compile and run. If you coded TODO 1.1 correctly, this should be all it
took to add a third cactus in the cycle. If you don’t see this, revisit TODO
1.1 to make sure it works for any length of the arrays. If it does all work,
submit your lab.
Submission Instructions
Zip up your entire project folder, including all source files, the Makefile, and everything
produced during compilation (including the .gba file). Submit this zip on Canvas. Name
your submission Lab03_FirstameLastname, for example: “Lab03_TraskUlgo.zip”.