Apply enu(opaque, &elem) to all the elements in the tree in a given range.
@param cmp a comparison function that returns < 0 for an element below the
range, > 0 for an element above the range and == 0 for an
element inside the range
@note The cmp function should use the same ordering used to construct the
tree.
Apply enu(opaque, &elem) to all the elements in the tree in a given range.
@param cmp a comparison function that returns < 0 for an element below the range, > 0 for an element above the range and == 0 for an element inside the range
@note The cmp function should use the same ordering used to construct the tree.