Fix FEN parser mistake on file index

src/fen.rs

@@ -29,7 +29,7 @@ pub fn from_fen(fen: &str) -> Result<Game, FenError> {
     })
 }
 
-fn piece_placement(pieces: &str) -> Result<Board, FenError> {
+pub fn piece_placement(pieces: &str) -> Result<Board, FenError> {
     let mut board = Board::empty_board();
     let (mut file, mut rank): (u8, u8) = (0, 7);
 
@@ -54,7 +54,7 @@ fn piece_placement(pieces: &str) -> Result<Board, FenError> {
                 continue;
             }
             n if n.is_numeric() => {
-                rank %= n.to_digit(10).unwrap_or(0) as u8;
+                file += n.to_digit(10).unwrap_or(0) as u8;
                 None
             }
             _ => {
@@ -64,9 +64,8 @@ fn piece_placement(pieces: &str) -> Result<Board, FenError> {
             }
         } {
             board.set_piece(Piece::new(1 << square, kind, color));
+            file += 1;
         };
-
-        file += 1;
     }
     Ok(board)
 }