!===============================================
! dotprod.f90

! dot product using derived type for vectors
!===============================================
program dotprod

  !-------------------------------------------
  ! module containing precision parameter
  !-------------------------------------------
  use prec_mod,  only: rk

  !-------------------------------------------
  ! module containing derived type
  !-------------------------------------------
  use rvec3_mod, only: rvec3

  implicit none
  integer :: i
  real(rk) :: c
  type(rvec3) :: a, b   !... Note type of vectors

  !----------------------------
  ! input vectors
  !----------------------------
  print*,'Enter first vector'
  read*, a%x            !... Note derived type notation
  print*,'Enter second vector'
  read*, b%x

  !----------------------------
  ! calculate dot product
  !----------------------------
  call dp(a%x, b%x, c)

  !----------------------------
  ! check magnitude
  !----------------------------
  if(abs(c) < 1.0e-6) then
     print*,'---------------------------------------------------'
     print*,'Warning: magnitude of dot product is less than 1e-6'
     print*,'---------------------------------------------------'
  endif

  !----------------------------
  ! print result
  !----------------------------
  print*,' '
  print*,'dot product = ', c

end program dotprod