The . characterThe
.-filter is a set filter that represents all 64 squares of the chessboard. It is thus always true.
.-filter can be used as a way to accept "any position" within the next/previous context:
next (. Ra3)matches a position where the white rook is on a3 following the current move.
As a set, the
.-filter is useful where one explicitly wants to consider all squares. For example:
countsquares 27 attack (Q .)
matches any position where the white queen attacks the maximum 27 squares.Examples