pacman/exercises/13/create_function/README.md

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Exercise: Create an isWall function

In this exercise we will write some helper functions for the game board.

The file Board.cpp defines functions to manipulate the game Board, for example finding where the walls and the portals are.

Background: Board.cpp

The Board itself is represented in memory as a 2 dimensional array. A cell in this grid can be for example walkable, a wall, a pellet, a super pellet or a portal.

Cell is an enum representing the different types of cells.

isWalkableForGhost and isWalkableForPacMan are two functions which need to check whether a cell is a wall.

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);
}

Exercise

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. Maybe we can lift that check into a separate function (call it isWall) to avoid repeating ourselves?

1. Create a function called isWall between cellAtPosition and isWalkableForPacMan that returns true if the GridPosition parameter is a wall. A function needs to be defined before it is called, so the order of functions is important. Try to define isWall after ``isWalkableForPacManor beforecellAtPosition`. It does not compile

2. Replace the checks within isWalkableForPacMan and isWalkableForGhost with your new function.

3. Check to see that the game still works as expected.