97 lines
2.9 KiB
R
97 lines
2.9 KiB
R
place_kings <- function(brd){
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###
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# Function that puts the two kings on the board
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# and makes sure that they are not adjacent
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###
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while (TRUE) {
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# generate positions for white and black kings
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rank_white <- sample(1:8, 1) ; file_white <- sample(1:8, 1)
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rank_black <- sample(1:8, 1) ; file_black <- sample(1:8, 1)
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# compute the differences between ranks and files
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diff_vec <- c(abs(rank_white - rank_black), abs(file_white - file_black))
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# if the two kings are not adjacent, place them on the board
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if (sum(diff_vec) > 2 | setequal(diff_vec, c(0,2))) {
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brd[rank_white, file_white] <- "K"
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brd[rank_black, file_black] <- "k"
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break
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}
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}
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return(brd)
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}
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pawn_on_extreme_ranks <- function(pc, pr){
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###
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# Function that checks whether a pawn is on the first or eight rank
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# (such a situation is not possible in chess)
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###
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if (pc %in% c("P","p") & pr %in% c(1,8))
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return(TRUE)
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else
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return(FALSE)
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}
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populate_board <- function(brd, wp, bp){
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###
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# Function that puts pieces on the board making sure that they
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# are not on the same squares, and verifying for pawn_on_extreme_ranks
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###
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# initialization
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piece_list <- c("P", "N", "B", "R", "Q")
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for (color in c("white", "black")){
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# iterate for white (first) and black (after) pieces
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if (color == "white"){
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n_pieces = wp
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pieces = piece_list
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}
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else {
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n_pieces = bp
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pieces = tolower(piece_list)
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}
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# place pieces one by one until we have them
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while (n_pieces != 0){
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piece_rank <- sample(1:8, 1) ; piece_file <- sample(1:8, 1)
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piece <- sample(pieces, 1)
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# check if square is empty and it is not a pawn on an extreme rank
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if (brd[piece_rank, piece_file] == " " & !pawn_on_extreme_ranks(piece, piece_rank)){
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brd[piece_rank, piece_file] <- piece
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n_pieces <- n_pieces - 1
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}
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}
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}
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return(brd)
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}
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fen_from_board <- function(brd){
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###
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# Function that prints out the FEN of a given input board
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###
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# create vector of positions by row
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fen <- apply(brd, 1, function(x) {
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r <- rle(x)
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paste(ifelse(r$values == " ", r$lengths, r$values), collapse = "")
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})
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# paste them together with separator '/' and add the final string
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fen <- paste(paste(fen, collapse = "/"), "w - - 0 1")
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return(fen)
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}
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generate_fen <- function(){
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###
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# This function calls all the functions above and generates
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# the board representation along with its FEN
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###
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# initialization
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board <- matrix(" ", nrow = 8, ncol = 8)
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# generate random amount of white and black pieces (kings excluded)
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n_pieces_white <- sample(0:31, 1) ; n_pieces_black <- sample(0:31, 1)
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# place kings on board
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board <- place_kings(board)
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# put other pieces on board
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board <- populate_board(board, wp = n_pieces_white, bp = n_pieces_black)
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# print board and FEN
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print(board)
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cat("\n")
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cat(fen_from_board(board))
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}
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generate_fen()
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