@sabaki/go-board

A Go board data type.

Installation

Use npm to install:

$ npm install @sabaki/go-board

Usage

const Board = require('@sabaki/go-board')

let board = new Board([
    [ 0, 0, 0,-1,-1,-1, 1, 0, 1, 1,-1,-1, 0,-1, 0,-1,-1, 1, 0],
    [ 0, 0,-1, 0,-1, 1, 1, 1, 0, 1,-1, 0,-1,-1,-1,-1, 1, 1, 0],
    [ 0, 0,-1,-1,-1, 1, 1, 0, 0, 1, 1,-1,-1, 1,-1, 1, 0, 1, 0],
    [ 0, 0, 0, 0,-1,-1, 1, 0, 1,-1, 1, 1, 1, 1, 1, 0, 1, 0, 0],
    [ 0, 0, 0, 0,-1, 0,-1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0],
    [ 0, 0,-1, 0, 0,-1,-1, 1, 0,-1,-1, 1,-1,-1, 0, 1, 0, 0, 1],
    [ 0, 0, 0,-1,-1, 1, 1, 1, 1, 1, 1, 1, 1,-1,-1,-1, 1, 1, 1],
    [ 0, 0,-1, 1, 1, 0, 1,-1,-1, 1, 0, 1,-1, 0, 1,-1,-1,-1, 1],
    [ 0, 0,-1,-1, 1, 1, 1, 0,-1, 1,-1,-1, 0,-1,-1, 1, 1, 1, 1],
    [ 0, 0,-1, 1, 1,-1,-1,-1,-1, 1, 1, 1,-1,-1,-1,-1, 1,-1,-1],
    [-1,-1,-1,-1, 1, 1, 1,-1, 0,-1, 1,-1,-1, 0,-1, 1, 1,-1, 0],
    [-1, 1,-1, 0,-1,-1,-1,-1,-1,-1, 1,-1, 0,-1,-1, 1,-1, 0,-1],
    [ 1, 1, 1, 1,-1, 1, 1, 1,-1, 1, 0, 1,-1, 0,-1, 1,-1,-1, 0],
    [ 0, 1,-1, 1, 1,-1,-1, 1,-1, 1, 1, 1,-1, 1,-1, 1, 1,-1, 1],
    [ 0, 0,-1, 1, 0, 0, 1, 1,-1,-1, 0, 1,-1, 1,-1, 1,-1, 0,-1],
    [ 0, 0, 1, 0, 1, 0, 1, 1, 1,-1,-1, 1,-1,-1, 1,-1,-1,-1, 0],
    [ 0, 0, 0, 0, 1, 1, 0, 1,-1, 0,-1,-1, 1, 1, 1, 1,-1,-1,-1],
    [ 0, 0, 1, 1,-1, 1, 1,-1, 0,-1,-1, 1, 1, 1, 1, 0, 1,-1, 1],
    [ 0, 0, 0, 1,-1,-1,-1,-1,-1, 0,-1,-1, 1, 1, 0, 1, 1, 1, 0]
])

let move = board.makeMove(1, [9, 4])

API

Sign Map

The board arrangement is represented by an array of arrays. Each of those subarrays represent one row, all containing the same number of integers. -1 denotes a white stone, 1 a black stone, and 0 represents an empty vertex.

Example

[[ 0, 0, 1, 0,-1,-1, 1, 0, 0],
 [ 1, 0, 1,-1,-1, 1, 1, 1, 0],
 [ 0, 0, 1,-1, 0, 1,-1,-1, 0],
 [ 1, 1, 1,-1,-1,-1, 1,-1, 0],
 [ 1,-1, 1, 1,-1, 1, 1, 1, 0],
 [-1,-1,-1,-1,-1, 1, 0, 0, 0],
 [ 0,-1,-1, 0,-1, 1, 1, 1, 1],
 [ 0, 0, 0, 0, 0,-1,-1,-1, 1],
 [ 0, 0, 0, 0, 0, 0, 0,-1, 0]]

Vertex

Board positions are represented by a vertex, i.e. an array of the form [x, y] where x and y are non-negative integers, zero-based coordinates. [0, 0] denotes the upper left position of the board.

---

class Board

Constructors

new Board([signMap])

• signMap <SignMap> (optional) - Default: []

Board.fromDimensions(width[, height])

• width <Integer>
• height <Integer> (optional) - Default: width

Returns a new Board instance with a sign map of the given dimensions that is filled with 0.

Properties

board.signMap

<SignMap> - The underlying sign map of the board.

board.width

<Integer> - The board width.

board.height

<Integer> - The board height.

Stone Arrangement Functions

board.get(vertex)

• vertex <Vertex>

Returns the sign at the given vertex.

board.set(vertex, sign)

• vertex <Vertex>
• sign <Integer> - One of -1, 0, or 1

Sets the sign at the given vertex. No validity checks will be made. This function mutates the board and returns this to enable chaining.

board.has(vertex)

• vertex <Vertex>

Returns a boolean whether the given vertex is valid or can be found on the board.

board.clear()

Sets the sign of all vertices to 0. This function mutates the board and returns this to enable chaining.

board.makeMove(sign, vertex[, options])

• sign <Integer> - One of -1, 0, or 1
• vertex <Vertex>
• options <Object> (optional)
  • preventOverwrite <Boolean> - Default: false
  • preventSuicide <Boolean> - Default: false
  • preventKo <Boolean> - Default: false

Returns a new board instance that represents the board state after the player who corresponds to the given sign makes a move at vertex. The capture count will also be updated correctly. If board is valid then the new returned board instance will also be valid. This function will not mutate board. If sign is 0 or vertex not valid, this function will be equivalent to clone().

If preventOverwrite is set to true, this function will throw an error if the attempted move is on a vertex that is already occupied by a stone.

If preventSuicide is set to true, this function will throw an error if the attempted move is a suicide.

If preventKo is set to true, this function will throw an error if the attempted move repeats the position that led to board.

board.analyzeMove(sign, vertex)

• sign <Integer> - One of -1, 0, or 1
• vertex <Vertex>

Analyzes the hypothetical move that the player who corresponds to the given sign would make at vertex. Returns an object with the following keys with boolean values:

• pass - Specifies if the move would be a pass (sign is 0 or vertex is not valid)
• overwrite - Specifies if the move would overwrite an occupied stone on the board
• capturing - Specifies if the move would capture some enemy stone
• suicide - Specifies if the move would end up in a suicide
• ko - Specifies if the move would repeat the position that led to board

Capture Count Functions

board.getCaptures(sign)

• sign <Integer> - One of -1 or 1

Returns the number of stones that the player, who corresponds to the given sign, captured.

board.setCaptures(sign, mutator)

• sign <Integer> - One of -1 or 1
• mutator <Function | Integer>

If mutator is a function of the following form

(prevCaptures: <Integer>) -> <Integer>

we will update the capture count of the player who corresponds to the given sign according to the mutator function. If mutator is an integer, we will directly set the capture count to mutator instead. This function mutates the board and returns this to enable chaining.

Board Property Functions

board.isSquare()

Equivalent to board.width === board.height.

board.isEmpty()

Returns true if signMap contains 0 only, otherwise false.

board.isValid()

Returns true if all chains have at least one liberty, otherwise false.

Topology Functions

board.getDistance(vertex1, vertex2)

• vertex1 <Vertex>
• vertex2 <Vertex>

Returns the Manhattan distance between the given vertices.

board.getNeighbors(vertex)

• vertex <Vertex>

Returns an array of vertices on the board that are exactly Manhattan distance 1 away from the given vertex.

board.getConnectedComponent(vertex, predicate)

• vertex <Vertex>
• predicate <Function>

predicate is a function of the following form:

(vertex: <Vertex>) -> <Boolean>

Returns a list of vertices that fulfill predicate and connect to vertex through a string of vertices that all fulfill predicate.

board.getChain(vertex)

• vertex <Vertex>

Equivalent to board.getConnectedComponent(vertex, v => board.get(v) === board.get(vertex)).

board.getRelatedChains(vertex)

• vertex <Vertex>

Returns an array of vertices of the same sign as vertex that belong to the same enemy area as vertex.

board.getLiberties(vertex)

• vertex <Vertex>

Returns an array of vertices that represents the liberties of the chain that vertex belongs to.

board.hasLiberties(vertex)

• vertex <Vertex>

Equivalent to board.getLiberties(vertex).length > 0, but faster.

Helper Functions

board.clone()

Returns a new Board instance that is equivalent to board, but mutations to either of them will not affect one another.

board.diff(otherBoard)

• board <Board>

Returns an array of vertices whose signs are not identical in board and otherBoard. If otherBoard has different dimensions from board, this will return null.

board.stringifyVertex(vertex)

• vertex <Vertex>

Returns a string that represents the given vertex. If vertex is invalid or not on the board, an empty string will be returned.

board.parseVertex(coord)

• coord <String>

Returns a vertex that the given coord represents. If coord is invalid or not on the board, [-1, -1] will be returned.

board.getHandicapPlacement(count)

• count <Integer>

Returns a list of vertices that represent the positions of black handicap stones.