# 1 "<stdin>"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "<stdin>"

module fold
! fold the ends inside
  use adj_mod
implicit none
  contains
  function fold_lop ( adj, add, x, y) result(stat)
    integer :: stat
    logical,intent(in) :: adj,add
    real,dimension(:) :: x,y
    call adjnull (adj,add,x,y )
    call fold_lop2(adj,add,x,y )
    stat=0
  end function
  subroutine fold_lop2(adj,add,x,y)
    logical,intent(in) :: adj,add
    real, dimension (:) :: x
    real, dimension (:) :: y
    integer :: nu, nr, np, nt
    nu = size (y)
    nt = size (x)
    np = (nt + nu) /2
    nr = (nt - nu) /2 + 1
    if (adj) then
      x (nt:np+1:-1) = y (nu-nt+np+1:nu ) + x (nt:np+1:-1)
      x (nr-1: 1:-1) = y ( 1:nr-1) + x (nr-1: 1:-1)
      x (nr:np) = y + x (nr:np)
    else
      y = y + x (nr:np)
      y ( 1:nr-1) = y ( 1:nr-1) + x (nr-1: 1:-1)
      y (nu-nt+np+1:nu ) = y (nu-nt+np+1:nu ) + x (nt:np+1:-1)
    end if
  end subroutine
  subroutine fold_close()
  end subroutine
end module