Chapter 1

TInt iLength; // Length - determined from type
TInt iRemaining; // Remaining unit squares
// Calculated members
TInt iStartX, iStartY; // Start position
TInt iDx, iDy; // Orientation vector
};
A ship's first attribute is its type, iType, which may be battleship, cruiser, destroyer, or
frigate. The type governs the length – 4, 3, 2, or 1 squares, respectively.
The relationship between type and length is encapsulated in the
TShip::TShip(TShipType) constructor: you specify a valid ship type, and the
constructor sets the length. There's also a default constructor, which is needed so that
arrays of TShips can be constructed in TFleet: the default constructor sets the ship type
to unknown and the length to zero.
A ship has a starting square and a direction vector, for example, a battleship starting at (3, 4)
with a direction vector of (0, 1) will cover squares (3, 4), (3, 5), (3, 6), and (3, 7). Clearly, the
same battleship could also be described by a starting square of (3, 7) and a direction vector
or (0, −1) – it doesn't matter.
The above information about ships is used during hit detection to work out whether a hit
request affects a particular ship (in iMyFleet). When a hit is registered, I decrement the
iRemaining count, which is initially set to the length of the ship. I can then tell when the
ship has been entirely sunk.
The ship-type enumeration is worth a second look. TShip::TShipType is passed to and
returned from many functions in the engine API. The ship type is an enumerated type,
including constants not only for the four real ship types, but artificial values for unknown and
sea. These are there to ensure that the ship-type enumeration is compatible with the square
states in TFleet.
Note
TShip::TShipType is represented in the engine's APIs and is used
throughout the higher-level code that plays Solo Ships and, indeed,
Battleships. The TFleet square states are private to TFleet. The
requirement to keep TFleet's square states in sync with TShipType is a
little awkward: initially I judged it tolerable in this small design, but on
reflection I'm guilty of microoptimization here – see the comment below.
Another small-time design practice is that I don't hide the data members of
TShip terribly well: in some contexts, I would have taken more trouble to
make data members private, and to provide public accessors. Again, that
didn't seem worth the trouble here.
There's nothing too difficult about TShip's implementation: check out engine.cpp for
details.
9.3.2 The Fleet Class
A fleet is an 8 × 8 grid of squares containing up to 10 ships. Here's the declaration:
class TFleet