Solutions

Here are the solutions to the exercises in this chapter.

Exercise 1

A pure function should not depend on or modify any state outside its scope. So, instead of relying on the global difficultyModifier value, we should pass it as a parameter:

[Pure]
public double CalculateDamage(Tower tower, Enemy enemy, double difficultyModifier)
{
     return tower.BaseDamage * enemy.DamageMultiplier * difficultyModifier;
}

Exercise 2

To isolate side effects, we’ll separate the pure logic from the I/O operations and state mutations:

public interface IFileReader
{
     string ReadAllText(string filePath);
}
public interface IEnemyRepository
{
     void AddEnemies(IEnumerable<Enemy> enemies);
}
public interface ILogger
{
     void Log(string message);
}
public class EnemyProcessor
{
     private readonly IFileReader _fileReader;
  ...