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