PROGRAM erityis
  IMPLICIT NONE
  INTRINSIC SIN, CSIN
  REAL :: x = 1.0, y = 0.0
  WRITE (*,*) 'Arvot:  ', SIN(x), SIN(CMPLX(x,y))
  WRITE (*,*) 'Erotus: ', testi(SIN, CSIN, x, y)
CONTAINS
  REAL FUNCTION testi(f1, f2, x, y)
    IMPLICIT NONE
    REAL, EXTERNAL :: f1
    COMPLEX, EXTERNAL :: f2
    REAL, INTENT(IN) :: x, y
    testi = ABS(f1(x) - f2(CMPLX(x,y)))
  END FUNCTION testi
END PROGRAM erityis