17 Language support library [language.support]

17.3 Implementation properties [support.limits]

17.3.4 Floating-point type properties [fp.style]

17.3.4.1 Type float_­round_­style [round.style]

namespace std {
  enum float_round_style {
    round_indeterminate       = -1,
    round_toward_zero         =  0,
    round_to_nearest          =  1,
    round_toward_infinity     =  2,
    round_toward_neg_infinity =  3
  };
}
The rounding mode for floating-point arithmetic is characterized by the values:
  • round_­indeterminate if the rounding style is indeterminable
  • round_­toward_­zero if the rounding style is toward zero
  • round_­to_­nearest if the rounding style is to the nearest representable value
  • round_­toward_­infinity if the rounding style is toward infinity
  • round_­toward_­neg_­infinity if the rounding style is toward negative infinity