Add legal chess captures exercise
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340
20_legal_captures.lua
Normal file
340
20_legal_captures.lua
Normal file
@ -0,0 +1,340 @@
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-- Write a function which takes a description of a chess position and
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-- returns a list of all legal captures from that position.
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--
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-- The position will be given as a table, containing the keys "turn",
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-- indicating which player it is to move, "board", which will contain
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-- a rank-major grid of pieces (that is, a list of ranks/rows). Each
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-- piece will be indicated by its unicode symbol. The lack of a piece
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-- will be indicated by nil. If the previous move was a pawn moving
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-- two places, the key "en_passant_target" will be set to a table with
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-- "rank" and "file" keys set to the (1-based) rank and file indices
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-- of the square passed over by the pawn.
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--
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-- For example, the starting position would be given as:
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--
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-- {
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-- turn = "white",
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-- board = {
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-- {"♖", "♘", "♗", "♕", "♔", "♗", "♘", "♖"},
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-- {"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
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-- {nil, nil, nil, nil, nil, nil, nil, nil},
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-- {nil, nil, nil, nil, nil, nil, nil, nil},
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-- {nil, nil, nil, nil, nil, nil, nil, nil},
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-- {nil, nil, nil, nil, nil, nil, nil, nil},
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-- {"♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎"},
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-- {"♜", "♞", "♝", "♛", "♚", "♝", "♞", "♜"},
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-- },
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-- }
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--
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-- Moves should be returned in figurine algebraic notation, without
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-- indicators for en passant, check or checkmate (i.e. no "e.p.", "+"
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-- or "#"). For example, "♞xc6" for a black night capturing on c6 and
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-- "exd7" for an e-file pawn capturing on d7. For the sake of
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-- simplicity, there's no requirement to disambiguate between two
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-- pieces of the same type when the notation for the capture would
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-- otherwise be the same (e.g. if two rooks can capture on the same
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-- square). However, there should be duplicate entries in the results
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-- list for each.
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--
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-- Solution --------------------------------------------------------------------
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function legal_captures(position)
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-- Your implementation here
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end
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-- Tests -----------------------------------------------------------------------
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local luaunit = require("luaunit.luaunit")
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function test_starting_position()
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local position = {
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turn = "white",
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board = {
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{"♖", "♘", "♗", "♕", "♔", "♗", "♘", "♖"},
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{"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{"♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎"},
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{"♜", "♞", "♝", "♛", "♚", "♝", "♞", "♜"},
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},
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}
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local expected = {}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_queens_gambit()
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local position = {
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turn = "black",
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board = {
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{"♖", "♘", "♗", "♕", "♔", "♗", "♘", "♖"},
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{"♙", "♙", nil, nil, "♙", "♙", "♙", "♙"},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, "♙", "♙", nil, nil, nil, nil},
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{nil, nil, nil, "♟︎", nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{"♟︎", "♟︎", "♟︎", nil, "♟︎", "♟︎", "♟︎", "♟︎"},
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{"♜", "♞", "♝", "♛", "♚", "♝", "♞", "♜"},
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},
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}
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local expected = {"dxc4"}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_scandinavian_defense()
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local position = {
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turn = "white",
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board = {
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{"♖", "♘", "♗", "♕", "♔", "♗", "♘", "♖"},
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{"♙", "♙", "♙", "♙", nil, "♙", "♙", "♙"},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, "♙", nil, nil, nil},
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{nil, nil, nil, "♟︎", nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{"♟︎", "♟︎", "♟︎", nil, "♟︎", "♟︎", "♟︎", "♟︎"},
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{"♜", "♞", "♝", "♛", "♚", "♝", "♞", "♜"},
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},
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}
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local expected = {"exd5"}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_knight_captures()
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local position = {
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turn = "black",
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board = {
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{"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
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{"♙", "♙", "♙", nil, "♙", "♙", "♙", "♙"},
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{"♙", "♙", nil, nil, nil, "♙", "♙", "♙"},
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{"♙", nil, nil, "♞", nil, nil, "♙", "♙"},
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{"♙", "♙", nil, nil, nil, "♙", "♙", "♙"},
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{"♙", "♙", "♙", nil, "♙", "♙", "♙", "♙"},
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{"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
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{"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
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},
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}
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local expected = {
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"♞xb3", "♞xb5", "♞xc2", "♞xc6", "♞xe2", "♞xe6", "♞xf3", "♞xf5",
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}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_knight_not_blocked()
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local position = {
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turn = "white",
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board = {
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, "♟︎", "♟︎", "♟︎", nil, nil},
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{nil, nil, nil, nil, "♟︎", nil, nil, nil},
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{nil, nil, "♟︎", "♟︎", "♘", nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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},
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}
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local expected = {"♘xd3", "♘xf3"}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_bishop_captures()
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local position = {
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turn = "black",
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board = {
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{"♙", nil, nil, nil, nil, nil, "♙", nil},
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{nil, nil, nil, "♙", nil, nil, "♙", nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, "♙", "♝", nil, nil, nil, "♙"},
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{nil, nil, nil, nil, "♙", nil, nil, nil},
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{nil, "♙", nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, "♙", nil, nil, nil, nil},
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},
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}
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local expected = {"♝xa2", "♝xb7", "♝xe6", "♝xg2"}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_bishop_blocked()
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local position = {
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turn = "black",
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board = {
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, "♙", nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, "♞", nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, "♝", nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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},
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}
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local expected = {}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_rook_captures()
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local position = {
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turn = "white",
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board = {
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{"♟︎", nil, nil, nil, nil, nil, "♟︎", nil},
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{nil, nil, nil, "♟︎", nil, nil, "♟︎", nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, "♟︎", "♖", nil, nil, nil, "♟︎"},
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{nil, nil, nil, nil, "♟︎", nil, nil, nil},
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{nil, "♟︎", nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, "♟︎", nil, nil, nil, nil},
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},
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}
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local expected = {"♖xc5", "♖xd3", "♖xd8", "♖xh5"}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_rook_blocked()
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local position = {
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turn = "white",
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board = {
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, "♖", "♙", nil, nil, nil, "♟︎", nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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},
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}
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local expected = {}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_queen_captures()
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local position = {
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turn = "black",
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board = {
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{nil, "♙", "♙", "♙", "♙", "♙", nil, "♙"},
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{"♙", "♙", "♙", nil, "♙", "♙", "♙", "♙"},
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{"♙", "♙", nil, nil, nil, "♙", "♙", "♙"},
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{"♙", nil, nil, "♛", nil, nil, "♙", nil},
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{"♙", "♙", nil, nil, nil, "♙", "♙", "♙"},
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{"♙", "♙", "♙", nil, "♙", "♙", "♙", "♙"},
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{nil, "♙", "♙", "♙", "♙", "♙", nil, "♙"},
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{"♙", "♙", "♙", nil, "♙", "♙", "♙", nil},
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},
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}
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local expected = {
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"♛xa4", "♛xb2", "♛xb6", "♛xd1", "♛xd7", "♛xf2", "♛xf6", "♛xg4",
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}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_queen_blocked()
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local position = {
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turn = "white",
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board = {
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, "♟︎", nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, "♙", nil, nil, nil, nil, nil},
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{nil, "♕", "♙", nil, nil, nil, "♟︎", nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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},
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}
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local expected = {}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_king_captures()
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local position = {
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turn = "black",
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board = {
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, "♙", "♙", "♙", nil, nil, nil},
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{nil, nil, "♙", "♚", "♙", nil, nil, nil},
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{nil, nil, "♙", "♙", "♙", nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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},
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}
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local expected = {"♚xc3","♚xc4","♚xc5","♚xd3","♚xd5","♚xe3","♚xe4","♚xe5",}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_en_passant()
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local position = {
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turn = "white",
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board = {
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, "♟︎", "♙", nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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},
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en_passant_target = {rank = 6, file = 4},
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}
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local expected = {"exd6"}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_cannot_capture_if_leads_to_check()
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local position = {
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turn = "white",
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board = {
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{nil, nil, nil, nil, "♔", nil, nil, nil},
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{nil, nil, nil, nil, "♗", nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, "♟︎", nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, "♜", nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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},
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en_passant_target = {rank = 6, file = 4},
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}
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local expected = {}
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luaunit.assertItemsEquals(legal_captures(position), expected)
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end
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function test_position_with_lots_of_captures()
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local position = {
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turn = "white",
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board = {
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{"♚", nil, nil, "♔", "♝", nil, nil, "♖"},
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{nil, "♖", "♜", "♕", "♞", "♕", "♘", nil},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{"♗", "♛", "♕", "♝", "♕", "♛", "♕", "♞"},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, "♕", "♝", "♕", "♛", "♕", "♘", "♗"},
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{nil, nil, nil, nil, nil, nil, nil, nil},
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{nil, nil, nil, "♜", "♕", "♛", nil, nil},
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},
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en_passant_target = {rank = 6, file = 4},
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}
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local expected = {
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"♔xe1", "♔xe2", "♔xc2", "♖xh4", "♖xe1",
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"♖xb4", "♖xc2", "♕xf4", "♕xb4", "♕xe1",
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"♕xd4", "♕xe2", "♕xc2", "♕xh4", "♕xd4",
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"♕xe1", "♕xf4", "♕xe2", "♘xh4", "♘xf4",
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"♘xe1", "♗xc6", "♗xc2", "♕xe6", "♕xe2",
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"♕xc6", "♕xc2", "♕xd4", "♕xb4", "♕xc6",
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"♕xc2", "♕xe6", "♕xe2", "♕xf4", "♕xd4",
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"♕xe6", "♕xe2", "♕xh4", "♕xf4", "♕xd8",
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"♕xd4", "♕xb4", "♕xc6", "♕xf8", "♕xf4",
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"♕xb4", "♕xd8", "♕xd4", "♕xe6", "♕xc6",
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"♕xd8", "♕xh4", "♕xd4", "♕xf8", "♕xf4",
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"♕xe6", "♘xf8", "♘xh4", "♘xf4", "♗xf8",
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"♗xf4", "♕xc6", "♕xe6", "♕xf8", "♕xd8",
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}
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local captures = legal_captures(position)
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luaunit.assertItemsEquals(captures, expected)
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end
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os.exit(luaunit.LuaUnit.run())
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