! 例題 8-8  スカラ三重積・ベクトル三重積 ［内部手続き関数 ］
PROGRAM ex8_8

  IMPLICIT NONE
  REAL, DIMENSION ( 1 : 3 ) :: a, b, c, bc

  PRINT *, "Input three vector's components:"
  READ *, a
  READ *, b
  READ *, c

  bc = vector_prod( b, c )
  PRINT '( " SP3 =", F10.3 )', scalar_prod( a, bc )
  PRINT '( " VP3 = (", 3F10.3, ")" )', vector_prod( a, bc )

CONTAINS

  FUNCTION vector_prod( x, y ) RESULT ( z )

    IMPLICIT NONE
    REAL, DIMENSION ( 1 : 3 ), INTENT ( IN ) :: x, y
    REAL, DIMENSION ( 1 : 3 ) :: z

    z( 1 ) = x( 2 ) * y( 3 ) - x( 3 ) * y( 2 )
    z( 2 ) = x( 3 ) * y( 1 ) - x( 1 ) * y( 3 )
    z( 3 ) = x( 1 ) * y( 2 ) - x( 2 ) * y( 1 )

  END FUNCTION vector_prod

  FUNCTION scalar_prod( x, y ) RESULT ( sp )

    IMPLICIT NONE
    REAL, DIMENSION( 1 : 3 ), INTENT ( IN ) :: x, y
    REAL :: sp

    sp = x( 1 ) * y( 1 ) + x( 2 ) * y( 2 ) + x( 3 ) * y( 3 )

  END FUNCTION scalar_prod

END PROGRAM ex8_8