btree_add_i8_zp2d Subroutine

      SUBROUTINE btree_add_i8_zp2d (tree, key, value, exists, existing_value, replace)
         TYPE(btree_i8_zp2d), INTENT(INOUT) :: tree
         INTEGER(KIND=keyt), INTENT(IN) :: key
         TYPE(btree_data_zp2d), INTENT(IN) :: value
         LOGICAL, INTENT(OUT), OPTIONAL :: exists
         TYPE(btree_data_zp2d), INTENT(OUT), OPTIONAL :: existing_value
         LOGICAL, INTENT(IN), OPTIONAL :: replace
         !
         TYPE(btree_node_i8_zp2d), POINTER :: node
         INTEGER :: ge_pos, position
         !
         IF (PRESENT(exists)) THEN
            CALL btree_find_full_i8_zp2d (tree, key, node, position, ge_pos, short=.TRUE.)
            IF (position .GT. 0) THEN
               exists = .TRUE.
               existing_value = node%values(position)
               IF (PRESENT(replace)) THEN
                  IF (replace) THEN
                     node%values(position) = value
                  END IF
               END IF
               RETURN
            ELSE
               exists = .FALSE.
            END IF
         ELSE
            CALL btree_find_leaf_i8_zp2d (tree, key, node, ge_pos)
         END IF
         CALL btree_add_into_i8_zp2d (tree, node, key, value, before=ge_pos)
         IF (PRESENT(exists)) existing_value = value
         tree%b%n = tree%b%n + 1
      END SUBROUTINE btree_add_i8_zp2d