grython7/haskell-chess

Implementing a chess game using Haskell

Implementing a chess game engine using Haskell

Assumptions for simplicity:

a) There are no promotions of pawns.

b) It is legal for a king to move to locations in which he will be threatened.

Functions

a) setBoard :: Board

The function does not take any inputs and returns a board representing the initial configuration depicted in Figure 1. Assume that the first turn is always on the white player. Example:

setBoard

(White, [R (’h’,1),N (’g’,1),B (’f’,1),K (’e’,1),
 Q (’d’,1),B (’c’,1),N (’b’,1),R (’a’,1),
 P (’h’,2),P (’g’,2),P (’f’,2),P (’e’,2),
 P (’d’,2),P (’c’,2),P (’b’,2),P (’a’,2)],
 [R (’h’,8),N (’g’,8),B (’f’,8),K (’e’,8),
 Q (’d’,8),B (’c’,8),N (’b’,8),R (’a’,8),
 P (’h’,7),P (’g’,7),P (’f’,7),P (’e’,7),
 P (’d’,7),P (’c’,7),P (’b’,7),P (’a’,7)])

b) visualizeBoard:: Board->String

The function takes as input a board and returns a visual representation of the board in a string. Black pieces are suffixed with ’B’ and white pieces are suffixed with ’W’.

visualizeBoard (setBoard)

|   | a  | b  | c  | d  | e  | f  | g  | h  |
|---|----|----|----|----|----|----|----|----|
| 8 | RB | NB | BB | QB | KB | BB | NB | RB |
| 7 | PB | PB | PB | PB | PB | PB | PB | PB |
| 6 |    |    |    |    |    |    |    |    |
| 5 |    |    |    |    |    |    |    |    |
| 4 |    |    |    |    |    |    |    |    |
| 3 |    |    |    |    |    |    |    |    |
| 2 | PW | PW | PW | PW | PW | PW | PW | PW |
| 1 | RW | NW | BW | QW | KW | BW | NW | RW |

c) isLegal:: Piece-> Board-> Location-> Bool

The function takes as input a piece, a board, and a location. It returns True if the move of the piece on the given board to the input location is legal, and False otherwise.

isLegal (P (’a’,7)) (setBoard) (’a’,5)

True

isLegal (P (’a’,7)) (setBoard) (’a’,4)

False

d) suggestMove:: Piece-> Board-> [Location]

The function takes as input a piece and a board and outputs a list of possible legal next locations for the piece. Example:

suggestMove (P (’e’,2)) (setBoard)

[(’e’,3),(’e’,4)]

e) move:: Piece-> Location-> Board-> Board

The function takes as input a piece, a location, and a board and returns a new updated board after the move is applied if it is a legal move. Otherwise, if the move is illegal, the function throws an appropriate error.

move (P (’a’,7)) (’a’,6) (setBoard)

Program error: This is White player’s turn, Black can’t move.

move (R (’h’,1)) (’h’,2) (setBoard))

Program error: Illegal move

Example for a valid movement

> move (N (’b’,3)) (’d’,4) (White, [R (’h’,1),N (’g’,1),B (’f’,1),
K (’e’,1), Q (’d’,1),B (’c’,1),N (’b’,3),R (’a’,1),
P (’h’,2),P (’g’,2),P (’f’,2),P (’e’,2),
P (’d’,2),P (’c’,2),P (’b’,2),P (’a’,2)] ,
[R (’h’,8),N (’g’,8),B (’f’,8),K (’e’,8),
Q (’d’,8),B (’c’,8),N (’b’,8),R (’a’,8),
P (’h’,7),P (’g’,7),P (’f’,7),P (’e’,7),
P (’d’,7),P (’c’,7),P (’b’,7),P (’a’,7)])

(Black,[R (’h’,1),N (’g’,1),B (’f’,1),K (’e’,1),
Q (’d’,1),B (’c’,1),N (’d’,4),R (’a’,1),
P (’h’,2),P (’g’,2),P (’f’,2),P (’e’,2),
P (’d’,2),P (’c’,2),P (’b’,2),P (’a’,2)],
[R (’h’,8),N (’g’,8),B (’f’,8),K (’e’,8),
Q (’d’,8),B (’c’,8),N (’b’,8),R (’a’,8),
P (’h’,7),P (’g’,7),P (’f’,7),P (’e’,7),
P (’d’,7),P (’c’,7),P (’b’,7),P (’a’,7)])