! 例題 3-3  三角波 ［多段階 IF 構文 ］
PROGRAM ex3_3

  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 = 2.0E0 - x
  ELSE
    f = 0.0E0
  END IF

  PRINT *, 'f(', x, ') =', f

END PROGRAM ex3_3