79 lines
2.7 KiB
Nim
79 lines
2.7 KiB
Nim
## Low-level handling of squares, board indeces and pieces
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import std/strutils
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import std/strformat
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type
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Square* = distinct int8
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## A square
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PieceColor* = enum
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## A piece color enumeration
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None = 0'i8,
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White,
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Black
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PieceKind* = enum
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## A chess piece enumeration
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Empty = 0'i8, # No piece
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Bishop = 'b',
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King = 'k'
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Knight = 'n',
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Pawn = 'p',
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Queen = 'q',
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Rook = 'r',
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Piece* = object
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## A chess piece
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color*: PieceColor
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kind*: PieceKind
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func nullPiece*: Piece {.inline.} = Piece(kind: Empty, color: None)
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func nullSquare*: Square {.inline.} = Square(-1'i8)
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func opposite*(c: PieceColor): PieceColor {.inline.} = (if c == White: Black else: White)
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func isValid*(a: Square): bool {.inline.} = a.int8 in 0..63
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func isLightSquare*(a: Square): bool {.inline.} = (a.int8 and 2) == 0
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func `==`*(a, b: Square): bool {.inline.} = a.int8 == b.int8
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func `!=`*(a, b: Square): bool {.inline.} = a.int8 != b.int8
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func `-`*(a, b: Square): Square {.inline.} = Square(a.int8 - b.int8)
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func `-`*(a: Square, b: SomeInteger): Square {.inline.} = Square(a.int8 - b.int8)
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func `-`*(a: SomeInteger, b: Square): Square {.inline.} = Square(a.int8 - b.int8)
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func `+`*(a, b: Square): Square {.inline.} = Square(a.int8 + b.int8)
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func `+`*(a: Square, b: SomeInteger): Square {.inline.} = Square(a.int8 + b.int8)
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func `+`*(a: SomeInteger, b: Square): Square {.inline.} = Square(a.int8 + b.int8)
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func colFromSquare*(square: Square): int8 = square.int8 mod 8 + 1
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func rowFromSquare*(square: Square): int8 = square.int8 div 8 + 1
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func makeSquare*(rank, file: SomeInteger): Square = Square((rank * 8) + file)
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proc toSquare*(s: string): Square {.discardable.} =
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## Converts a square square from algebraic
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## notation to its corresponding row and column
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## in the chess grid (0 indexed)
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if len(s) != 2:
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raise newException(ValueError, "algebraic position must be of length 2")
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var s = s.toLowerAscii()
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if s[0] notin 'a'..'h':
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raise newException(ValueError, &"algebraic position has invalid first character ('{s[0]}')")
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if s[1] notin '1'..'8':
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raise newException(ValueError, &"algebraic position has invalid second character ('{s[1]}')")
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return Square((s[0].uint8 - uint8('a')) + ((s[1].uint8 - uint8('1')) xor 7) * 8)
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proc toAlgebraic*(square: Square): string {.inline.} =
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## Converts a square from our internal rank/file
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## notation to a square in algebraic notation
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let
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file = char('a'.uint8 + (square.uint64 and 7))
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rank = char('1'.uint8 + ((square.uint64 div 8) xor 7))
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return &"{file}{rank}"
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proc `$`*(square: Square): string = square.toAlgebraic() |