@std/decimal.ms#

Import each required symbol with import Name from "@std/decimal.ms".

Decimal Native type#

An exact decimal value. Conversions are explicit because binary floats may round.

type Decimal:
    fn to_float() -> Float:
    fn truncate_to_int() -> Optional[Int]:
    fn round(places: Int, mode: Optional[RoundingMode] = none) -> Result[Decimal, NumberError]:
    fn to_fixed(digits: Int, mode: Optional[RoundingMode] = none) -> Result[String, NumberError]:

Decimal.round#

Rounds exactly to a multiple of 10^-places, without converting to Float. Places range from -6144 through 6176; negative places round tens, hundreds, etc. Invalid places return InvalidInput; an unrepresentable result returns OutOfRange. Omitted or none mode selects HalfEven. This does not preserve trailing zeros or change arithmetic.

fn round(places: Int, mode: Optional[RoundingMode] = none) -> Result[Decimal, NumberError]:

Decimal.to_fixed#

Rounds exactly and prints plain decimal notation with exactly digits fractional digits. Digits range from 0 through 6176; invalid digits return InvalidInput. HalfEven is the default; rounded zero has no minus sign. Trailing zeros are retained.

fn to_fixed(digits: Int, mode: Optional[RoundingMode] = none) -> Result[String, NumberError]:

Decimal.to_float#

Converts to the nearest Float, which can lose precision because binary floats cannot represent most decimal fractions exactly. Values beyond the Float range convert to an infinity.

fn to_float() -> Float:

Decimal.truncate_to_int#

Discards the fractional part toward zero and returns the integer, so -2.9 gives -2. Returns none when the integer part does not fit in signed 64 bits.

fn truncate_to_int() -> Optional[Int]:

RoundingMode Alternative#

How a Decimal rounds to a multiple of the requested power of ten.

type RoundingMode:
    case HalfEven
    case HalfAwayFromZero
    case TowardZero
    case Floor
    case Ceil

RoundingMode.Ceil#

Rounds toward positive infinity.

case Ceil

RoundingMode.Floor#

Rounds toward negative infinity.

case Floor

RoundingMode.HalfAwayFromZero#

Nearest value; an exact tie rounds away from zero.

case HalfAwayFromZero

RoundingMode.HalfEven#

Nearest value; an exact tie chooses the even coefficient.

case HalfEven

RoundingMode.TowardZero#

Discards the fractional coefficient toward zero.

case TowardZero