Simplify the exercise

exercises/small/131-functions-and-parameters.md

@@ -1,59 +1,44 @@
-# Functions and Parameter Passing
+# 131. Functions and Parameter Passing
 
 In this exercise we will write some helper functions for the game board.
 
-The game board is defined in the `Board.cpp` file and the exported functions are described in `Board.hpp`
+The file [`Board.cpp`](../../lib/Board.cpp) defines functions to manipulate the game Board, for example finding where
+the walls and the portals are.
 
-## Board.cpp/hpp
+## Board.cpp
 
-The structure of these files is as follows. The `cpp` file starts with including the `Board.hpp` file and all of its
+The Board itself is represented in memory as a 2 dimensional array. A cell in this grid can be for example walkable, a
-contents. Then we open a namespace and define how many rows and columns the board will have. We also create an enum that
+wall, a pellet, a super pellet or a portal.
-defines what each cell value means on the board itself.
 
-Then we have the actual board. A two dimensional array of integers. This will be the layout of the game board. We use
+`Cell` is an enum representing the different types of cells.
-integers and not the Cell enum we defined above so we can use the numbers directly, the `enum class` is strongly typed,
-you can see this when we check for values.
 
-Below the board are the helper functions. Some of them are static (only visible within this file) and some are not,
+`isWalkableForGhost` and `isWalkableForPacMan` are two functions which need to check whether a cell is a wall.
-those that are not should have a similar function description in the `Board.hpp` file. For example:
 
 ```cpp
-// Board.hpp
-bool isWalkableForPacMan(GridPosition point);
-
-// Board.cpp
 bool isWalkableForPacMan(GridPosition point) {
  return cellAtPosition(point) != Cell::wall && cellAtPosition(point) != Cell::pen;
 }
+
+bool isWalkableForGhost(GridPosition point, GridPosition origin, bool isEyes) {
+ const Cell cell = cellAtPosition(point);
+ if (cell == Cell::wall)
+   return false;
+ return isEyes || isInPen(origin) || !isInPen(point);
+}
 ```
 
-## Board Unit Tests
-
-The game board is covered by unit tests. They are located in the `testBoard.cpp` file within the `test` directory. They
-don't check every single tile on the board but they do assume that the board shape is not changed significantly. If you
-change the board layout you might have to change some of the unit tests to match.
-
-Unit tests are broken down into test cases, in this file it is focused on a test case per function. A `TEST_CASE` takes
-two arguments, a test name and a tag. The test name needs to be unique and for the tag we use the section of the game we
-are testing. Think of them like functions that are called when testing.
-
 ## Exercise
 
-Lets add a simple helper function.
+Let's add a simple helper function.
 
 You might notice that `isWalkableForPacMan` and `isWalkableForGhost` both call `cellAtPosition` with a `GridPosition`
-variable and check if it is a wall.
+variable and check if it is a wall. Maybe we can lift that check into a separate function (call it `isWall`) to avoid
+repeating ourselves?
 
-1. Create a function called `isWall` below `cellAtPosition` that returns true if the `GridPosition` variable sent in is
+1. Create a function called `isWall` between `cellAtPosition` and `isWalkableForPacMan` that returns true if
-   a wall. Remember to also create the same function signature in the `Board.hpp` file so this helper function can be
+   the `GridPosition` parameter is a wall. A function needs to be defined before it is called, so the order of functions
-   used elsewhere in the project if needed.
+   is important. Try to define `isWall` after ``isWalkableForPacMan` or before `cellAtPosition`. It does not compile
 
 2. Replace the checks within `isWalkableForPacMan` and `isWalkableForGhost` with your new function.
 
-3. Add a new unit test `TEST_CASE` for your function. Since you already added `isWall` to the `Board.hpp` file it should
+3. Check to see that the game still works as expected.
-   be accessible within the `testBoard.cpp` file. Check for a couple of cases, similarly to the `isWalkableForPacMan`
-   test. Remember since the unit tests are not inside of the `pacman` namespace, we need to append `pacman::` to the
-   function calls.
-
-4. Compile the project and run the unit tests. They should all be passing and if they are not then check which unit test
-   is failing and figure out what was causing the issue. If all goes well you can run the game.