! triangle pulse
PROGRAM ex3_4

  REAL :: x, f

  PRINT *, 'x ? '
  READ *, x

  IF ( x < 0.0E0 ) THEN
    f = 0.0E0
  ELSE IF ( x < 1.0E0 ) THEN
    f = x
  ELSE IF ( x < 2.0E0 ) THEN
    f = - x + 2.0E0
  ELSE
    f = 0.0E0
  END IF

  PRINT *, x, f

END PROGRAM ex3_4