Enum RoundingMode

pub enum RoundingMode {
    Up,
    Down,
    Ceiling,
    Floor,
    HalfUp,
    HalfDown,
    HalfEven,
}

Determines how to calculate the last digit of the number

Default rounding mode is HalfUp

Variants

Up

Always round away from zero

• 5.5 → 6.0
• 2.5 → 3.0
• 1.6 → 2.0
• 1.1 → 2.0
• -1.1 → -2.0
• -1.6 → -2.0
• -2.5 → -3.0
• -5.5 → -6.0

Down

Always round towards zero

• 5.5 → 5.0
• 2.5 → 2.0
• 1.6 → 1.0
• 1.1 → 1.0
• -1.1 → -1.0
• -1.6 → -1.0
• -2.5 → -2.0
• -5.5 → -5.0

Ceiling

Towards +∞

• 5.5 → 6.0
• 2.5 → 3.0
• 1.6 → 2.0
• 1.1 → 2.0
• -1.1 → -1.0
• -1.6 → -1.0
• -2.5 → -2.0
• -5.5 → -5.0

Floor

Towards -∞

• 5.5 → 5.0
• 2.5 → 2.0
• 1.6 → 1.0
• 1.1 → 1.0
• -1.1 → -2.0
• -1.6 → -2.0
• -2.5 → -3.0
• -5.5 → -6.0

HalfUp

Round to ‘nearest neighbor’, or up if ending decimal is 5

• 5.5 → 6.0
• 2.5 → 3.0
• 1.6 → 2.0
• 1.1 → 1.0
• -1.1 → -1.0
• -1.6 → -2.0
• -2.5 → -3.0
• -5.5 → -6.0

HalfDown

Round to ‘nearest neighbor’, or down if ending decimal is 5

• 5.5 → 5.0
• 2.5 → 2.0
• 1.6 → 2.0
• 1.1 → 1.0
• -1.1 → -1.0
• -1.6 → -2.0
• -2.5 → -2.0
• -5.5 → -5.0

HalfEven

Round to ‘nearest neighbor’, if equidistant, round towards nearest even digit

• 5.5 → 6.0
• 2.5 → 2.0
• 1.6 → 2.0
• 1.1 → 1.0
• -1.1 → -1.0
• -1.6 → -2.0
• -2.5 → -2.0
• -5.5 → -6.0

Implementations

impl RoundingMode

pub fn round_pair(&self, sign: Sign, pair: (u8, u8), trailing_zeros: bool) -> u8

Perform the rounding operation

Parameters

• sign (Sign) - Sign of the number to be rounded
• pair (u8, u8) - The two digits in question to be rounded. i.e. to round 0.345 to two places, you would pass (4, 5). As decimal digits, they must be less than ten!
• trailing_zeros (bool) - True if all digits after the pair are zero. This has an effect if the right hand digit is 0 or 5.

Returns

Returns the first number of the pair, rounded. The sign is not preserved.

Examples

• To round 2341, pass in Plus, (4, 1), true → get 4 or 5 depending on scheme
• To round -0.1051, to two places: Minus, (0, 5), false → returns either 0 or 1
• To round -0.1, pass in true, (0, 1) → returns either 0 or 1

Calculation of pair of digits from full number, and the replacement of that number should be handled separately

pub fn round_u32( &self, at_digit: NonZeroU8, sign: Sign, value: u32, trailing_zeros: bool, ) -> u32

Round value at particular digit, returning replacement digit

Parameters

• at_digit (NonZeroU8) - 0-based index of digit at which to round. 0 would be the first digit, and would

• sign (Sign) - Sign of the number to be rounded

• value (u32) - The number containing digits to be rounded.

• trailing_zeros (bool) - True if all digits after the value are zero.

Returns

Returns the first number of the pair, rounded. The sign is not preserved.

Examples

• To round 823418, at digit-index 3: 3, Plus, 823418, true → 823000 or 824000, depending on scheme
• To round -100205, at digit-index 1: 1, Minus, 100205, true → 100200 or 100210

Calculation of pair of digits from full number, and the replacement of that number should be handled separately

Trait Implementations

impl Clone for RoundingMode

fn clone(&self) -> RoundingMode

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for RoundingMode

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for RoundingMode

Return compile-time constant default rounding mode

Defined by RUST_BIGDECIMAL_DEFAULT_ROUNDING_MODE at compile time

fn default() -> Self

Returns the “default value” for a type.

impl Hash for RoundingMode

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for RoundingMode

fn eq(&self, other: &RoundingMode) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for RoundingMode

impl Eq for RoundingMode

impl StructuralPartialEq for RoundingMode