FITPACK_MESSAGE Function

      pure function FITPACK_MESSAGE(ierr) result(msg)
         integer, intent(in) :: ierr
         character(len=:), allocatable :: msg

         select case (ierr)
            case (FITPACK_OK); msg = 'Success!'
            case (FITPACK_INTERPOLATING_OK); msg = 'Success! (interpolation)'
            case (FITPACK_LEASTSQUARES_OK); msg = 'Success! (least-squares)'
            case (FITPACK_INSUFFICIENT_STORAGE); msg = 'Insufficient Storage'
            case (FITPACK_S_TOO_SMALL); msg = 'Smoothing parameter is too small'
            case (FITPACK_MAXIT); msg = 'Infinite loop detected'
            case (FITPACK_TOO_MANY_KNOTS); msg = 'More knots than data points'
            case (FITPACK_OVERLAPPING_KNOTS); msg = 'Overlapping knots found'
            case (FITPACK_INVALID_RANGE); msg = 'Invalid variable range'
            case (FITPACK_INPUT_ERROR); msg = 'Invalid input'
            case (FITPACK_TEST_ERROR); msg = 'Test(s) failed'
            case default; msg = 'UNKNOWN ERROR'
         end select

      end function FITPACK_MESSAGE