# 1 "<stdin>"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "<stdin>"
module igrad1
! gradient in one dimension
  use adj_mod
implicit none
  contains
  function igrad1_lop ( adj, add, xx, yy) result(stat)
    integer :: stat
    logical,intent(in) :: adj,add
    real,dimension(:) :: xx,yy
    call adjnull (adj,add,xx,yy )
    call igrad1_lop2(adj,add,xx,yy )
    stat=0
  end function
  subroutine igrad1_lop2(adj,add,xx,yy)
    logical,intent(in) :: adj,add
    real, dimension (:) :: xx
    real, dimension (:) :: yy
    integer i
    do i= 1, size(xx)-1
      if ( adj) then
        xx(i+1) = xx(i+1) + yy(i) ! resembles equation (1.2)
        xx(i ) = xx(i ) - yy(i)
      else
        yy(i) = yy(i) + xx(i+1) - xx(i) ! resembles equation (1.1)
      end if
    end do
  end subroutine
  subroutine igrad1_close()
  end subroutine
end module