/// <summary>
/// Applies the specified effect on the given state (modifies him!).
/// </summary>
/// <param name="effect">Effect for the application.</param>
/// <param name="state">State.</param>
/// <param name="substitution">Variables substitution.</param>
public void Apply(IEffect effect, IState state, ISubstitution substitution)
{
State = state;
Substitution = substitution;
effect.Accept(this);
Substitution = null;
State = null;
}
