README
¶
| ⛔ NOTICE: USE OF THIS LIBRARY IN ANZ SYSTEMS IS STRICTLY PROHIBITED. ⛔ |
|---|
| This library is currently in development and has not undergone a thorough correctness assessment or security audit. It is therefore NOT suitable for production use until full approval is granted by the ANZ open source committee and this notice removed. |
decimal
This library implements fixed-precision decimal numbers based on IEEE 754R standard; https://ieeexplore.ieee.org/document/4674342 More info can be found at: http://speleotrove.com/decimal/
Features
- Decimal64, partial implementation of the ieee-754R standard
- Half up and half even rounding
- Up to 3 times faster than arbitrary precision decimal libraries in Go
Goals
- To implement 128 bit decimal
Installation and use
Run go get github.com/anz-bank/decimal
package main
import (
"fmt"
"github.com/anz-bank/decimal"
)
func main() {
var a decimal.Decimal64
b := decimal.MustParse64("0.1")
c := decimal.MustParse64("0.3")
d := decimal.New64FromInt64(123456)
fmt.Println(a, b, c, d)
}
Docs
https://godoc.org/github.com/anz-bank/decimal
Why decimal
Binary floating point numbers are fundamentally flawed when it comes to representing exact numbers in a decimal world. Just like 1/3 can't be represented in base 10 (it evaluates to 0.3333333333 repeating), 1/10 can't be represented in binary.
The solution is to use a decimal floating point number.
Binary floating point numbers (often just called floating point numbers) are usually in the form
Sign * Significand * 2 ^ exp
and decimal floating point numbers change this to
Sign * Significand * 10 ^ exp
This eliminates the decimal fraction problem, as the base is in 10.
Why fixed precision
Most implementations of a decimal floating point datatype implement an 'arbitrary precision' type, which often uses an underlying big int. This gives flexibility in that as the number grows, the number of bits assigned to the number grows ( and thus 'arbitrary precision'). This library is different as it specifies a 64 bit decimal datatype as specified in the ieee-754R standard. This gives the sacrifice of being able to represent arbitrarily large numbers, but is faster than other arbitrary precision libraries.
Documentation
¶
Index ¶
- Variables
- type Context64
- type Decimal64
- func (d Decimal64) Abs() Decimal64
- func (d Decimal64) Add(e Decimal64) Decimal64
- func (d Decimal64) Append(buf []byte, format byte, prec int) []byte
- func (d Decimal64) Class() string
- func (d Decimal64) Cmp(e Decimal64) int
- func (d Decimal64) FMA(e, f Decimal64) Decimal64
- func (d Decimal64) Float64() float64
- func (d Decimal64) Format(s fmt.State, format rune)
- func (d *Decimal64) GobDecode(buf []byte) error
- func (d Decimal64) GobEncode() ([]byte, error)
- func (d Decimal64) Int64() int64
- func (d Decimal64) IsInf() bool
- func (d Decimal64) IsInt() bool
- func (d Decimal64) IsNaN() bool
- func (d Decimal64) IsQNaN() bool
- func (d Decimal64) IsSNaN() bool
- func (d Decimal64) IsSubnormal() bool
- func (d Decimal64) IsZero() bool
- func (d Decimal64) MarshalJSON() ([]byte, error)
- func (d Decimal64) MarshalText() []byte
- func (d Decimal64) Mul(e Decimal64) Decimal64
- func (d Decimal64) Neg() Decimal64
- func (d Decimal64) Quo(e Decimal64) Decimal64
- func (d *Decimal64) Scan(state fmt.ScanState, verb rune) error
- func (d Decimal64) Sign() int
- func (d Decimal64) Signbit() bool
- func (d Decimal64) Sqrt() Decimal64
- func (d Decimal64) String() string
- func (d Decimal64) Sub(e Decimal64) Decimal64
- func (d Decimal64) Text(format byte, prec int) string
- func (d *Decimal64) UnmarshalJSON(data []byte) error
- func (d *Decimal64) UnmarshalText(text []byte) error
Constants ¶
This section is empty.
Variables ¶
var DefaultContext = Context64{roundHalfUp}
DefaultContext is the context that Arithmetic functions will use in order to do calculations
var E64 = newFromParts(0, -15, 2718281828459045)
E64 represents e (lim[n→∞](1+1/n)ⁿ).
var Infinity64 = Decimal64{inf64}
Infinity64 represents ∞ as a Decimal64.
var Max64 = newFromParts(0, expMax, maxSig)
Max64 is the maximum number representable with a Decimal64.
var Min64 = newFromParts(0, -398, 1)
Min64 is the smallest number that is subnormal possible with Decimal64.
var NegInfinity64 = Decimal64{neg64 | inf64}
NegInfinity64 represents -∞ as a Decimal64.
var NegMax64 = newFromParts(1, expMax, maxSig)
NegMax64 is the minimum finite number (most negative) possible with Decimal64 (negative).
var NegOne64 = newFromParts(1, -15, decimal64Base)
NegOne64 represents -1 as a Decimal64.
var NegZero64 = newFromParts(1, 0, 0)
NegZero64 represents -0 as a Decimal64.
var One64 = newFromParts(0, -15, decimal64Base)
One64 represents 1 as a Decimal64.
var Pi64 = newFromParts(0, -15, 3141592653589793)
Pi64 represents π.
var QNaN64 = Decimal64{0x7c << 56}
QNaN64 represents a quiet NaN as a Decimal64.
var SNaN64 = Decimal64{0x7e << 56}
SNaN64 represents a signalling NaN as a Decimal64.
var Zero64 = newFromParts(0, 0, 0)
Zero64 represents 0 as a Decimal64.
Functions ¶
This section is empty.
Types ¶
type Context64 ¶
type Context64 struct {
// contains filtered or unexported fields
}
Context64 stores the rounding type for arithmetic operations.
type Decimal64 ¶
type Decimal64 struct {
// contains filtered or unexported fields
}
Decimal64 represents an IEEE 754 64-bit floating point decimal number. It uses the binary representation method. Decimal64 is intentionally a struct to ensure users don't accidentally cast it to uint64
func MustParse64 ¶
MustParse64 parses a string as a Decimal64 and returns the value or panics if the string doesn't represent a valid Decimal64.
func New64FromInt64 ¶
New64FromInt64 returns a new Decimal64 with the given value.
func (Decimal64) Cmp ¶
Cmp returns:
-2 if d or e is NaN -1 if d < e 0 if d == e (incl. -0 == 0, -Inf == -Inf, and +Inf == +Inf) +1 if d > e
func (Decimal64) IsSubnormal ¶
IsSubnormal returns true iff d is a subnormal.
func (Decimal64) MarshalJSON ¶
MarshalText implements the encoding.TextMarshaler interface.
func (Decimal64) MarshalText ¶
MarshalText implements the encoding.TextMarshaler interface.
func (Decimal64) Text ¶
Text converts the floating-point number x to a string according to the given format and precision prec.
func (*Decimal64) UnmarshalJSON ¶
UnmarshalText implements the encoding.TextUnmarshaler interface.
func (*Decimal64) UnmarshalText ¶
UnmarshalText implements the encoding.TextUnmarshaler interface.
Source Files