insert.f90

TYPE :: node
	character (len=2) :: value
	type(node), pointer :: left, right
END TYPE

recursive subroutine insert (t,value)
	IMPLICIT NONE
	TYPE(node), pointer, INTENT(IN) :: t ! really a tree
	character(len=2), intent(in) :: value
	
	! if subtree empty put number at root
	IF (.not. associated(t)) then
		allocate(t)
		t % value = value
		nullify(t%left)
		nullify(t%right)
	! otherwise, add to tree
	ELSE IF (value < t % value) THEN
		call insert (t%left, value)
	ELSE
		call insert (t%right, value)
	END IF
END subroutine insert