Struct Decimal 

pub struct Decimal { /* private fields */ }

An exact base-10 fixed-point number: an integer coefficient divided by a power of ten. The value is coefficient · 10^(−scale), so 19.99 is coefficient = 1999, scale = 2. Money lives here — 0.1 + 0.2 is exactly 0.3, never the 0.30000000000000004 of a binary float, and a long ledger of sums never drifts.

+, −, × are exact (multiplication adds the scales); ÷ and Decimal::rescale round under an explicit RoundingMode because base-10 division need not terminate. Equality and ordering are by value (1.0 == 1.00 == 1); scale is only a display hint. The coefficient is a BigInt, so the value is unbounded and exact — the i128 fast path is the documented performance follow-up.

Implementations

impl Decimal

pub fn from_bigint(coeff: BigInt) -> Decimal

The integer coeff at scale 0.

pub fn from_i64(x: i64) -> Decimal

pub fn from_coeff_scale(coeff: BigInt, scale: u32) -> Decimal

Construct directly from a coefficient and scale (value = coeff / 10^scale).

pub fn zero() -> Decimal

pub fn one() -> Decimal

pub fn scale(&self) -> u32

pub fn coefficient(&self) -> &BigInt

pub fn is_zero(&self) -> bool

pub fn is_negative(&self) -> bool

pub fn negated(&self) -> Decimal

pub fn abs(&self) -> Decimal

pub fn to_rational(&self) -> Rational

Exact view as a Rational (coeff / 10^scale) — lossless, the bridge that keeps Decimal inside the exact tower.

pub fn from_rational( value: &Rational, scale: u32, mode: RoundingMode, ) -> Decimal

The fixed-point value nearest value at the given scale, rounded under mode.

pub fn rescale(&self, scale: u32, mode: RoundingMode) -> Decimal

Restate at a different scale. Widening appends zeros (exact); narrowing drops digits and rounds under mode.

pub fn add(&self, other: &Decimal) -> Decimal

pub fn sub(&self, other: &Decimal) -> Decimal

pub fn mul(&self, other: &Decimal) -> Decimal

Exact product: coefficients multiply, scales add.

pub fn div( &self, other: &Decimal, scale: u32, mode: RoundingMode, ) -> Option<Decimal>

Quotient rounded to scale under mode. None when other == 0 — base-10 division need not terminate, so the caller names the precision it wants.

pub fn to_le_bytes(&self) -> (bool, Vec<u8>, u32)

Sign + little-endian coefficient bytes + scale — the wire form (the inverse of Decimal::from_le_bytes). Reuses BigInt’s exact byte serialization.

pub fn from_le_bytes(negative: bool, bytes: &[u8], scale: u32) -> Decimal

pub fn parse(s: &str) -> Option<Decimal>

Parse plain decimal notation: optional sign, optional integer part, optional .fraction. "19.99", "-0.005", ".5", "5.", "42" all parse; the scale is the count of fractional digits. None on a non-digit or an empty value.

Trait Implementations

impl Clone for Decimal

fn clone(&self) -> Decimal

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Decimal

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

Formats the value using the given formatter.

impl Display for Decimal

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

Formats the value using the given formatter.

impl From<BigInt> for Decimal

fn from(x: BigInt) -> Self

Converts to this type from the input type.

impl From<i64> for Decimal

fn from(x: i64) -> Self

Converts to this type from the input type.

impl Hash for Decimal

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 Ord for Decimal

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Decimal

fn eq(&self, other: &Self) -> 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 PartialOrd for Decimal

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Eq for Decimal