More logic

[yallop]

Logic to support animation, etc., as previously discussed.

Boards now remember the effects of the previous move, which makes it possible to support scoring and provenance. Only shift_left_helper really needed to change, which is a promising sign for the tutorial structure.

Terminology reverted to say "square" rather than "tile". There are probably a few places where we should still be saying "tile".

Provenance

(I suspect the semantics of a couple of these functions isn't quite what @dbuenzli needs. Just let me know if so; I'll be around this morning.)

val is_new_square : square -> bool
(** [is_new_square t] indicates whether [t] is freshly inserted. *)

val square_shift : square -> int option
(** [square_shift t] indicates how far the current occupant shifted to
    reach its current position. *)

val square_previous : square -> int option
(** [square_previous_value t] indicates the previous value of the
    current occupant of the square. *)

End-of-game

val is_board_winning : board -> bool
(** [is_board_winning board] is [true] iff the [board] is a winning board. *)

Scoring

Scoring is move-based, not board-based: points equal to the sum of the result are awarded for combining two tiles.

val last_move_score : board -> int
(** [last_move_score board] is the score achieved by the last move. *)

Misc

The code needs simplifying a bit to use a minimal set of language features, but let's leave that until last. There are also likely to be more opportunities to simplify the implementation along the lines of 49990e6b.

[dbuenzli]

A few things.

1. I still need a game over condition. I guess that's when any move returns the same board.
2. I can do with square_previous but it is really not practical. As when I'm in a position I need to search the board with square_shift to get the value of the tile that moved by square_shift (i.e. do positioning business and introduce something like G2048.square_at : board -> int * int -> tile. If you give me the value of the tile that shifted. I can render with a single fold_squares.
3. Aren't the things that move tiles ? That should then be tile_shift and (maybe) shifted_tile_value.

[dbuenzli]

Also API wise I think it would be better to expose the provenance type. The reason is that this would make it clear in the interface that given a square t you cannot have is_new_square t = true and square_shift t = Some _ .

[dbuenzli]

And either I understood nothing to Leo's explanation about board games but it should also be is_new_tile rather than is_new_square. But as I said I'd rather have a tile_provenance : square -> provenance option function or even directly square_tile : square -> (int * provenance) option

[yallop]

I still need a game over condition. I guess that's when any move returns the same board.

See 40ed539.

[yallop]

Also API wise I think it would be better to expose the provenance type.

See 62695fa.

(Other changes to follow).

[yallop]

Aren't the things that move tiles ? That should then be tile_shift and (maybe) shifted_tile_value. And either I understood nothing to Leo's explanation about board games but it should also be is_new_tile rather than is_new_square

See 4f8a742.

[yallop]

I can do with square_previous but it is really not practical. As when I'm in a position I need to search the board with square_shiftto get the value of the tile that moved by square_shift (i.e. do positioning business and introduce something like G2048.square_at : board -> int * int -> tile. If you give me the value of the tile that shifted. I can render with a single fold_squares.

I'm not sure I follow here. What API would you rather have?

[yallop]

New approach to provenance in a6fc9a8.

type provenance = { shift : int; value : int }
val square_provenance : square -> provenance list

Subsumes/supersedes tile_shift, shifted_tile_value, is_new_tile.

[dbuenzli]

Sorry I was busy this afternoon with @samoht trying to define an ocamlfindless world. But the interface looks good. Will work on this tomorrow.

[yallop]

Ok -- I'll merge for now, and we can patch if necessary tomorrow.