! --- scalar and vector products of two vectors ---
PROGRAM main

  IMPLICIT NONE
  REAL :: s
  TYPE vector
    REAL :: x, y, z
  END TYPE vector
  TYPE(vector) :: a, b, c

  PRINT '(1X, A)', 'Input 3 components of the first vector: '
  READ *, a
  PRINT '(1X, A)', 'Input 3 components of the second vector: '
  READ *, b

  s = a%x * b%x + a%y * b%y + a%z * b%z       ! s = a * b とは書けない
  PRINT '("a.b = ", F6.3)', s
  c = vector_product(a,b)
  PRINT '("a^b = (", F6.3, ",", F6.3, ",", F6.3, ")")', c

CONTAINS

  FUNCTION vector_product( u, v ) RESULT( w )

    IMPLICIT NONE
    TYPE(vector), INTENT(IN) :: u, v
    TYPE(vector) :: w

    w%x = u%y * v%z - u%z * v%y
    w%y = u%z * v%x - u%x * v%z
    w%z = u%x * v%y - u%y * v%x

  END FUNCTION

END PROGRAM main