The type of a function which transforms a game.

• The first three fields represent the state of the game.
• These are augmented by the game's history, i.e. the sequence of moves.
• For efficiency the list of available moves is stored.

Count the number of plies available to the specified player.

• Roll-back the specified game until the start, returning each previous game paired with the ply which was then made.
• The list-head contains the most recent ply, while the tail contains the first.

Sort the lists of destinations to faciliate testing for equality.

• Retrieve the recorded value, or generate the list of moves available to the player of the specified logical colour.
• CAVEAT: doesn't account for game-termination.

Retrieve the recorded value, or generate the list of moves available to the next player.

Gets the sequence of turns, with the latest at the head & the opening one last.

Gets the sequence of turns in the order they occured.

The last turn, if there was one.

• True if the specified move is valid, given the implied piece & the current state of the game.
• N.B.: it is considered valid to take a King, one just never has the opportunity, since the game terminates the move before.

Validates the move-type then forwards the request to validateQualifiedMove.

Update the position-hash of the game prior to application of the last move.

Constructor.

Smart constructor.

Constructor. For convenience, the following assumptions are made in the absence of any move-history:

• The next player's logical colour is assumed to be White;
• Provided that the King is at its starting coordinates, then all Rooks which exist at their starting coordinates are considered to be castleable;
• There're zero previous turns.

Construct AvailableQualifiedMoves for the player of the specified logical colour.

• Moves the referenced piece between the specified coordinates.
• As a result of the turn, the next logical colour is changed, the moves available to each player are updated, & any reason for game-termination recorded.
• CAVEAT: no validation of the turn is performed since the move may have been automatically selected & therefore known to be valid.
• CAVEAT: doesn't account for any previous game-termination when updating getAvailableQualifiedMovesByLogicalColour.

Construct a turn & relay the request to takeTurn.

Construct a qualifiedMove & relay the request to "applyQualifiedMove".

Constructs eitherQualifiedMoves from the data provided, validating & applying each in the specified order.

Provided that the game hasn't already terminated, update the termination-reason according to whether the specified result implies either a draw by agreement or a resignation.

Resignation by the player who currently holds the choice of move.

Whether the specified QualifiedMove is valid.

Whether the specified EitherQualifiedMove is valid.

Whether the game has been terminated.

Forwards request to State.CastleableRooksByLogicalColour.

• Whether the specified game's positions have converged, & despite perhaps having reached this position from different move-sequences, now have equal opportunities.
• CAVEAT: this is different from equality.
• CAVEAT: this test doesn't account for the possibility that one game may more quickly be drawn according to either the "Seventy-five-move Rule" or "Five-fold Repetition".
• CAVEAT: though convenient, this function shouldn't be called for repeated tests against a constant position, resulting in unnecessary repeated construction of that position.

Whether the state of the specified games is different.