! vector and array
MODULE vector_and_array

  IMPLICIT NONE
  TYPE vector
    REAL :: x, y, z
  END TYPE vector

  INTERFACE ASSIGNMENT(=)
    MODULE PROCEDURE vector_to_array
  END INTERFACE

  INTERFACE ASSIGNMENT(=)
    MODULE PROCEDURE array_to_vector
  END INTERFACE

CONTAINS

  SUBROUTINE vector_to_array( a, v )

    IMPLICIT NONE
    TYPE(vector), INTENT(IN) :: v
    REAL, INTENT(OUT) :: a(1:3)

    a = (/ v%x, v%y, v%z /)

  END SUBROUTINE vector_to_array

  SUBROUTINE array_to_vector( v, a )

    IMPLICIT NONE
    REAL, INTENT(IN) :: a(1:3)
    TYPE(vector), INTENT(OUT) :: v

    v = vector( a(1), a(2), a(3) )

  END SUBROUTINE array_to_vector

END MODULE vector_and_array
!
! main
!
PROGRAM main

  USE vector_and_array
  IMPLICIT NONE
  TYPE(vector) :: u
  REAL :: w(1:3)

  PRINT '(1X, A)', 'Input 3d-vector components: '
  READ *, u

  w = u
  u = 2E0 * w
  PRINT '(3F8.3)', u

END PROGRAM main