static const std::float_round_style round_style; | (until C++11) | |

static constexpr std::float_round_style round_style; | (since C++11) |

The value of `std::numeric_limits<T>::round_style`

identifies the rounding style used by the floating-point type `T`

whenever a value that is not one of the exactly repesentable values of `T`

is stored in an object of that type.

`T` | value of `std::numeric_limits<T>::round_style` |
---|---|

/* non-specialized */ | `std::round_toward_zero` |

`bool` | `std::round_toward_zero` |

`char` | `std::round_toward_zero` |

`signed char` | `std::round_toward_zero` |

`unsigned char` | `std::round_toward_zero` |

`wchar_t` | `std::round_toward_zero` |

`char8_t` (C++20) | `std::round_toward_zero` |

`char16_t` (C++11) | `std::round_toward_zero` |

`char32_t` (C++11) | `std::round_toward_zero` |

`short` | `std::round_toward_zero` |

`unsigned short` | `std::round_toward_zero` |

`int` | `std::round_toward_zero` |

`unsigned int` | `std::round_toward_zero` |

`long` | `std::round_toward_zero` |

`unsigned long` | `std::round_toward_zero` |

`long long` (C++11) | `std::round_toward_zero` |

`unsigned long long` (C++11) | `std::round_toward_zero` |

`float` | usually `std::round_to_nearest` |

`double` | usually `std::round_to_nearest` |

`long double` | usually `std::round_to_nearest` |

These values are constants, and do not reflect the changes to the rounding made by `std::fesetround`

. The changed values may be obtained from `FLT_ROUNDS`

or `std::fegetround`

.

The decimal value `0.1`

cannot be represented by a binary floating-point type. When stored in an IEEE-754 `double`

, it falls between 0x1.9999999999999*2-4

and 0x1.999999999999a*2-4

. Rounding to nearest representable value results in 0x1.999999999999a*2-4

.

Similarly, the decimal value 0.3, which is between 0x1.3333333333333*2-2

and 0x1.3333333333334*2-2

is rounded to nearest and is stored as 0x1.3333333333333*2-2

.

#include <iostream> #include <limits> int main() { std::cout << std::hexfloat << "The decimal 0.1 is stored in a double as " << 0.1 << '\n' << "The decimal 0.3 is stored in a double as " << 0.3 << '\n' << "The rounding style is " << std::numeric_limits<double>::round_style << '\n'; }

Output:

The decimal 0.1 is stored in a double as 0x1.999999999999ap-4 The decimal 0.3 is stored in a double as 0x1.3333333333333p-2 The rounding style is 1

indicates floating-point rounding modes (enum) |

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