descendant

The descendant filter takes two position filters as arguments enclosed in parentheses. The descendant filter matches the position if the position represented by its first argument is a descendant of the position represented by its second argument.

   descendant(x y)

We say that position x is a descendant of position y if, starting from position y there is a nonempty sequence of moves from the PGN file that reach position x.

If x and y are mainline positions, then x is a descendant of y if and only if the position id of x is greater than the position id of y. Thus, in this case, one can test if x is a descendant of y simply by doing:

  x>y

Note that descendant(x y) is equivalent to ancestor(y x) .