decimal

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 Go to latest Published: Apr 12, 2024 License: MIT Imports: 8 Imported by: 35,482

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decimal

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Arbitrary-precision fixed-point decimal numbers in go.

Note: Decimal library can "only" represent numbers with a maximum of 2^31 digits after the decimal point.

Features

  • The zero-value is 0, and is safe to use without initialization
  • Addition, subtraction, multiplication with no loss of precision
  • Division with specified precision
  • Database/sql serialization/deserialization
  • JSON and XML serialization/deserialization

Install

Run go get github.com/shopspring/decimal

Requirements

Decimal library requires Go version >=1.10

Documentation

http://godoc.org/github.com/shopspring/decimal

Usage

package main

import (
	"fmt"
	"github.com/shopspring/decimal"
)

func main() {
	price, err := decimal.NewFromString("136.02")
	if err != nil {
		panic(err)
	}

	quantity := decimal.NewFromInt(3)

	fee, _ := decimal.NewFromString(".035")
	taxRate, _ := decimal.NewFromString(".08875")

	subtotal := price.Mul(quantity)

	preTax := subtotal.Mul(fee.Add(decimal.NewFromFloat(1)))

	total := preTax.Mul(taxRate.Add(decimal.NewFromFloat(1)))

	fmt.Println("Subtotal:", subtotal)                      // Subtotal: 408.06
	fmt.Println("Pre-tax:", preTax)                         // Pre-tax: 422.3421
	fmt.Println("Taxes:", total.Sub(preTax))                // Taxes: 37.482861375
	fmt.Println("Total:", total)                            // Total: 459.824961375
	fmt.Println("Tax rate:", total.Sub(preTax).Div(preTax)) // Tax rate: 0.08875
}

Alternative libraries

When working with decimal numbers, you might face problems this library is not perfectly suited for. Fortunately, thanks to the wonderful community we have a dozen other libraries that you can choose from.
Explore other alternatives to find the one that best fits your needs :)

  • cockroachdb/apd - arbitrary precision, mutable and rich API similar to big.Int, more performant than this library
  • alpacahq/alpacadecimal - high performance, low precision (12 digits), fully compatible API with this library
  • govalues/decimal - high performance, zero-allocation, low precision (19 digits)
  • greatcloak/decimal - fork focusing on billing and e-commerce web application related use cases, includes out-of-the-box BSON marshaling support

FAQ

Why don't you just use float64?

Because float64 (or any binary floating point type, actually) can't represent numbers such as 0.1 exactly.

Consider this code: http://play.golang.org/p/TQBd4yJe6B You might expect that it prints out 10, but it actually prints 9.999999999999831. Over time, these small errors can really add up!

Why don't you just use big.Rat?

big.Rat is fine for representing rational numbers, but Decimal is better for representing money. Why? Here's a (contrived) example:

Let's say you use big.Rat, and you have two numbers, x and y, both representing 1/3, and you have z = 1 - x - y = 1/3. If you print each one out, the string output has to stop somewhere (let's say it stops at 3 decimal digits, for simplicity), so you'll get 0.333, 0.333, and 0.333. But where did the other 0.001 go?

Here's the above example as code: http://play.golang.org/p/lCZZs0w9KE

With Decimal, the strings being printed out represent the number exactly. So, if you have x = y = 1/3 (with precision 3), they will actually be equal to 0.333, and when you do z = 1 - x - y, z will be equal to .334. No money is unaccounted for!

You still have to be careful. If you want to split a number N 3 ways, you can't just send N/3 to three different people. You have to pick one to send N - (2/3*N) to. That person will receive the fraction of a penny remainder.

But, it is much easier to be careful with Decimal than with big.Rat.

Why isn't the API similar to big.Int's?

big.Int's API is built to reduce the number of memory allocations for maximal performance. This makes sense for its use-case, but the trade-off is that the API is awkward and easy to misuse.

For example, to add two big.Ints, you do: z := new(big.Int).Add(x, y). A developer unfamiliar with this API might try to do z := a.Add(a, b). This modifies a and sets z as an alias for a, which they might not expect. It also modifies any other aliases to a.

Here's an example of the subtle bugs you can introduce with big.Int's API: https://play.golang.org/p/x2R_78pa8r

In contrast, it's difficult to make such mistakes with decimal. Decimals behave like other go numbers types: even though a = b will not deep copy b into a, it is impossible to modify a Decimal, since all Decimal methods return new Decimals and do not modify the originals. The downside is that this causes extra allocations, so Decimal is less performant. My assumption is that if you're using Decimals, you probably care more about correctness than performance.

License

The MIT License (MIT)

This is a heavily modified fork of fpd.Decimal, which was also released under the MIT License.

Documentation

Overview

Package decimal implements an arbitrary precision fixed-point decimal.

The zero-value of a Decimal is 0, as you would expect.

The best way to create a new Decimal is to use decimal.NewFromString, ex: 

n, err := decimal.NewFromString("-123.4567")
n.String() // output: "-123.4567"

To use Decimal as part of a struct: 

type StructName struct {
    Number Decimal
}

Note: This can "only" represent numbers with a maximum of 2^31 digits after the decimal point.

Index

Examples

Constants

This section is empty.

Variables

View Source 
var DivisionPrecision = 16

DivisionPrecision is the number of decimal places in the result when it doesn't divide exactly.

Example: 

d1 := decimal.NewFromFloat(2).Div(decimal.NewFromFloat(3))
d1.String() // output: "0.6666666666666667"
d2 := decimal.NewFromFloat(2).Div(decimal.NewFromFloat(30000))
d2.String() // output: "0.0000666666666667"
d3 := decimal.NewFromFloat(20000).Div(decimal.NewFromFloat(3))
d3.String() // output: "6666.6666666666666667"
decimal.DivisionPrecision = 3
d4 := decimal.NewFromFloat(2).Div(decimal.NewFromFloat(3))
d4.String() // output: "0.667"
View Source 
var ExpMaxIterations = 1000

ExpMaxIterations specifies the maximum number of iterations needed to calculate precise natural exponent value using ExpHullAbrham method.

View Source 
var MarshalJSONWithoutQuotes = false

MarshalJSONWithoutQuotes should be set to true if you want the decimal to be JSON marshaled as a number, instead of as a string. WARNING: this is dangerous for decimals with many digits, since many JSON unmarshallers (ex: Javascript's) will unmarshal JSON numbers to IEEE 754 double-precision floating point numbers, which means you can potentially silently lose precision.

View Source 
var PowPrecisionNegativeExponent = 16

PowPrecisionNegativeExponent specifies the maximum precision of the result (digits after decimal point) when calculating decimal power. Only used for cases where the exponent is a negative number. This constant applies to Pow, PowInt32 and PowBigInt methods, PowWithPrecision method is not constrained by it.

Example: 

d1, err := decimal.NewFromFloat(15.2).PowInt32(-2)
d1.String() // output: "0.0043282548476454"

decimal.PowPrecisionNegativeExponent = 24
d2, err := decimal.NewFromFloat(15.2).PowInt32(-2)
d2.String() // output: "0.004328254847645429362881"
View Source 
var Zero = New(0, 1)

Zero constant, to make computations faster. Zero should never be compared with == or != directly, please use decimal.Equal or decimal.Cmp instead.

Functions

func RescalePair added in v1.2.0 

func RescalePair(d1 Decimal, d2 Decimal) (Decimal, Decimal)

RescalePair rescales two decimals to common exponential value (minimal exp of both decimals)

Types

type Decimal 

type Decimal struct {
	// contains filtered or unexported fields
}

Decimal represents a fixed-point decimal. It is immutable. number = value * 10 ^ exp

func Avg 

func Avg(first Decimal, rest ...Decimal) Decimal

Avg returns the average value of the provided first and rest Decimals

func Max 

func Max(first Decimal, rest ...Decimal) Decimal

Max returns the largest Decimal that was passed in the arguments.

To call this function with an array, you must do: 

Max(arr[0], arr[1:]...)

This makes it harder to accidentally call Max with 0 arguments.

func Min 

func Min(first Decimal, rest ...Decimal) Decimal

Min returns the smallest Decimal that was passed in the arguments.

To call this function with an array, you must do: 

Min(arr[0], arr[1:]...)

This makes it harder to accidentally call Min with 0 arguments.

func New 

func New(value int64, exp int32) Decimal

New returns a new fixed-point decimal, value * 10 ^ exp.

func NewFromBigInt 

func NewFromBigInt(value *big.Int, exp int32) Decimal

NewFromBigInt returns a new Decimal from a big.Int, value * 10 ^ exp

func NewFromBigRat added in v1.4.0 

func NewFromBigRat(value *big.Rat, precision int32) Decimal

NewFromBigRat returns a new Decimal from a big.Rat. The numerator and denominator are divided and rounded to the given precision.

Example: 

d1 := NewFromBigRat(big.NewRat(0, 1), 0)    // output: "0"
d2 := NewFromBigRat(big.NewRat(4, 5), 1)    // output: "0.8"
d3 := NewFromBigRat(big.NewRat(1000, 3), 3) // output: "333.333"
d4 := NewFromBigRat(big.NewRat(2, 7), 4)    // output: "0.2857"

func NewFromFloat 

func NewFromFloat(value float64) Decimal

NewFromFloat converts a float64 to Decimal.

The converted number will contain the number of significant digits that can be represented in a float with reliable roundtrip. This is typically 15 digits, but may be more in some cases. See https://www.exploringbinary.com/decimal-precision-of-binary-floating-point-numbers/ for more information.

For slightly faster conversion, use NewFromFloatWithExponent where you can specify the precision in absolute terms.

NOTE: this will panic on NaN, +/-inf

Example 
fmt.Println(NewFromFloat(123.123123123123).String())
fmt.Println(NewFromFloat(.123123123123123).String())
fmt.Println(NewFromFloat(-1e13).String())

Output:

123.123123123123
0.123123123123123
-10000000000000

func NewFromFloat32 added in v1.1.0 

func NewFromFloat32(value float32) Decimal

NewFromFloat32 converts a float32 to Decimal.

The converted number will contain the number of significant digits that can be represented in a float with reliable roundtrip. This is typically 6-8 digits depending on the input. See https://www.exploringbinary.com/decimal-precision-of-binary-floating-point-numbers/ for more information.

For slightly faster conversion, use NewFromFloatWithExponent where you can specify the precision in absolute terms.

NOTE: this will panic on NaN, +/-inf

Example 
fmt.Println(NewFromFloat32(123.123123123123).String())
fmt.Println(NewFromFloat32(.123123123123123).String())
fmt.Println(NewFromFloat32(-1e13).String())

Output:

123.12312
0.123123124
-10000000000000

func NewFromFloatWithExponent 

func NewFromFloatWithExponent(value float64, exp int32) Decimal

NewFromFloatWithExponent converts a float64 to Decimal, with an arbitrary number of fractional digits.

Example: 

NewFromFloatWithExponent(123.456, -2).String() // output: "123.46"

func NewFromFormattedString added in v1.3.0 

func NewFromFormattedString(value string, replRegexp *regexp.Regexp) (Decimal, error)

NewFromFormattedString returns a new Decimal from a formatted string representation. The second argument - replRegexp, is a regular expression that is used to find characters that should be removed from given decimal string representation. All matched characters will be replaced with an empty string.

Example: 

r := regexp.MustCompile("[$,]")
d1, err := NewFromFormattedString("$5,125.99", r)

r2 := regexp.MustCompile("[_]")
d2, err := NewFromFormattedString("1_000_000", r2)

r3 := regexp.MustCompile("[USD\\s]")
d3, err := NewFromFormattedString("5000 USD", r3)

func NewFromInt added in v1.2.0 

func NewFromInt(value int64) Decimal

NewFromInt converts an int64 to Decimal.

Example: 

NewFromInt(123).String() // output: "123"
NewFromInt(-10).String() // output: "-10"

func NewFromInt32 added in v1.2.0 

func NewFromInt32(value int32) Decimal

NewFromInt32 converts an int32 to Decimal.

Example: 

NewFromInt(123).String() // output: "123"
NewFromInt(-10).String() // output: "-10"

func NewFromString 

func NewFromString(value string) (Decimal, error)

NewFromString returns a new Decimal from a string representation. Trailing zeroes are not trimmed.

Example: 

d, err := NewFromString("-123.45")
d2, err := NewFromString(".0001")
d3, err := NewFromString("1.47000")

func NewFromUint64 added in v1.4.0 

func NewFromUint64(value uint64) Decimal

NewFromUint64 converts an uint64 to Decimal.

Example: 

NewFromUint64(123).String() // output: "123"

func RequireFromString added in v1.0.1 

func RequireFromString(value string) Decimal

RequireFromString returns a new Decimal from a string representation or panics if NewFromString had returned an error.

Example: 

d := RequireFromString("-123.45")
d2 := RequireFromString(".0001")

func Sum 

func Sum(first Decimal, rest ...Decimal) Decimal

Sum returns the combined total of the provided first and rest Decimals

func (Decimal) Abs 

func (d Decimal) Abs() Decimal

Abs returns the absolute value of the decimal.

func (Decimal) Add 

func (d Decimal) Add(d2 Decimal) Decimal

Add returns d + d2.

func (Decimal) Atan added in v1.1.0 

func (d Decimal) Atan() Decimal

Atan returns the arctangent, in radians, of x.

func (Decimal) BigFloat added in v1.2.0 

func (d Decimal) BigFloat() *big.Float

BigFloat returns decimal as BigFloat. Be aware that casting decimal to BigFloat might cause a loss of precision.

func (Decimal) BigInt added in v1.2.0 

func (d Decimal) BigInt() *big.Int

BigInt returns integer component of the decimal as a BigInt.

func (Decimal) Ceil 

func (d Decimal) Ceil() Decimal

Ceil returns the nearest integer value greater than or equal to d.

func (Decimal) Cmp 

func (d Decimal) Cmp(d2 Decimal) int

Cmp compares the numbers represented by d and d2 and returns: 

-1 if d <  d2
 0 if d == d2
+1 if d >  d2

func (Decimal) Coefficient 

func (d Decimal) Coefficient() *big.Int

Coefficient returns the coefficient of the decimal. It is scaled by 10^Exponent()

func (Decimal) CoefficientInt64 added in v1.3.0 

func (d Decimal) CoefficientInt64() int64

CoefficientInt64 returns the coefficient of the decimal as int64. It is scaled by 10^Exponent() If coefficient cannot be represented in an int64, the result will be undefined.

func (Decimal) Compare added in v1.4.0 

func (d Decimal) Compare(d2 Decimal) int

Compare compares the numbers represented by d and d2 and returns: 

-1 if d <  d2
 0 if d == d2
+1 if d >  d2

func (Decimal) Copy added in v1.3.0 

func (d Decimal) Copy() Decimal

Copy returns a copy of decimal with the same value and exponent, but a different pointer to value.

func (Decimal) Cos added in v1.1.0 

func (d Decimal) Cos() Decimal

Cos returns the cosine of the radian argument x.

func (Decimal) Div 

func (d Decimal) Div(d2 Decimal) Decimal

Div returns d / d2. If it doesn't divide exactly, the result will have DivisionPrecision digits after the decimal point.

func (Decimal) DivRound 

func (d Decimal) DivRound(d2 Decimal, precision int32) Decimal

DivRound divides and rounds to a given precision i.e. to an integer multiple of 10^(-precision) 

for a positive quotient digit 5 is rounded up, away from 0
if the quotient is negative then digit 5 is rounded down, away from 0

Note that precision<0 is allowed as input.

func (Decimal) Equal 

func (d Decimal) Equal(d2 Decimal) bool

Equal returns whether the numbers represented by d and d2 are equal.

func (Decimal) Equals deprecated 

func (d Decimal) Equals(d2 Decimal) bool

Deprecated: Equals is deprecated, please use Equal method instead.

func (Decimal) ExpHullAbrham added in v1.3.0 

func (d Decimal) ExpHullAbrham(overallPrecision uint32) (Decimal, error)

ExpHullAbrham calculates the natural exponent of decimal (e to the power of d) using Hull-Abraham algorithm. OverallPrecision argument specifies the overall precision of the result (integer part + decimal part).

ExpHullAbrham is faster than ExpTaylor for small precision values, but it is much slower for large precision values.

Example: 

NewFromFloat(26.1).ExpHullAbrham(2).String()    // output: "220000000000"
NewFromFloat(26.1).ExpHullAbrham(20).String()   // output: "216314672147.05767284"

func (Decimal) ExpTaylor added in v1.3.0 

func (d Decimal) ExpTaylor(precision int32) (Decimal, error)

ExpTaylor calculates the natural exponent of decimal (e to the power of d) using Taylor series expansion. Precision argument specifies how precise the result must be (number of digits after decimal point). Negative precision is allowed.

ExpTaylor is much faster for large precision values than ExpHullAbrham.

Example: 

d, err := NewFromFloat(26.1).ExpTaylor(2).String()
d.String()  // output: "216314672147.06"

NewFromFloat(26.1).ExpTaylor(20).String()
d.String()  // output: "216314672147.05767284062928674083"

NewFromFloat(26.1).ExpTaylor(-10).String()
d.String()  // output: "220000000000"

func (Decimal) Exponent 

func (d Decimal) Exponent() int32

Exponent returns the exponent, or scale component of the decimal.

func (Decimal) Float64 

func (d Decimal) Float64() (f float64, exact bool)

Float64 returns the nearest float64 value for d and a bool indicating whether f represents d exactly. For more details, see the documentation for big.Rat.Float64

func (Decimal) Floor 

func (d Decimal) Floor() Decimal

Floor returns the nearest integer value less than or equal to d.

func (*Decimal) GobDecode 

func (d *Decimal) GobDecode(data []byte) error

GobDecode implements the gob.GobDecoder interface for gob serialization.

func (Decimal) GobEncode 

func (d Decimal) GobEncode() ([]byte, error)

GobEncode implements the gob.GobEncoder interface for gob serialization.

func (Decimal) GreaterThan 

func (d Decimal) GreaterThan(d2 Decimal) bool

GreaterThan (GT) returns true when d is greater than d2.

func (Decimal) GreaterThanOrEqual 

func (d Decimal) GreaterThanOrEqual(d2 Decimal) bool

GreaterThanOrEqual (GTE) returns true when d is greater than or equal to d2.

func (Decimal) InexactFloat64 added in v1.3.0 

func (d Decimal) InexactFloat64() float64

InexactFloat64 returns the nearest float64 value for d. It doesn't indicate if the returned value represents d exactly.

func (Decimal) IntPart 

func (d Decimal) IntPart() int64

IntPart returns the integer component of the decimal.

func (Decimal) IsInteger added in v1.3.0 

func (d Decimal) IsInteger() bool

IsInteger returns true when decimal can be represented as an integer value, otherwise, it returns false.

func (Decimal) IsNegative added in v1.1.0 

func (d Decimal) IsNegative() bool

IsNegative return 

true if d < 0
false if d == 0
false if d > 0

func (Decimal) IsPositive added in v1.1.0 

func (d Decimal) IsPositive() bool

IsPositive return 

true if d > 0
false if d == 0
false if d < 0

func (Decimal) IsZero added in v1.1.0 

func (d Decimal) IsZero() bool

IsZero return 

true if d == 0
false if d > 0
false if d < 0

func (Decimal) LessThan 

func (d Decimal) LessThan(d2 Decimal) bool

LessThan (LT) returns true when d is less than d2.

func (Decimal) LessThanOrEqual 

func (d Decimal) LessThanOrEqual(d2 Decimal) bool

LessThanOrEqual (LTE) returns true when d is less than or equal to d2.

func (Decimal) Ln added in v1.4.0 

func (d Decimal) Ln(precision int32) (Decimal, error)

Ln calculates natural logarithm of d. Precision argument specifies how precise the result must be (number of digits after decimal point). Negative precision is allowed.

Example: 

d1, err := NewFromFloat(13.3).Ln(2)
d1.String()  // output: "2.59"

d2, err := NewFromFloat(579.161).Ln(10)
d2.String()  // output: "6.3615805046"

func (Decimal) MarshalBinary 

func (d Decimal) MarshalBinary() (data []byte, err error)

MarshalBinary implements the encoding.BinaryMarshaler interface.

func (Decimal) MarshalJSON 

func (d Decimal) MarshalJSON() ([]byte, error)

MarshalJSON implements the json.Marshaler interface.

func (Decimal) MarshalText 

func (d Decimal) MarshalText() (text []byte, err error)

MarshalText implements the encoding.TextMarshaler interface for XML serialization.

func (Decimal) Mod 

func (d Decimal) Mod(d2 Decimal) Decimal

Mod returns d % d2.

func (Decimal) Mul 

func (d Decimal) Mul(d2 Decimal) Decimal

Mul returns d * d2.

func (Decimal) Neg 

func (d Decimal) Neg() Decimal

Neg returns -d.

func (Decimal) NumDigits added in v1.3.0 

func (d Decimal) NumDigits() int

NumDigits returns the number of digits of the decimal coefficient (d.Value)

func (Decimal) Pow 

func (d Decimal) Pow(d2 Decimal) Decimal

Pow returns d to the power of d2. When exponent is negative the returned decimal will have maximum precision of PowPrecisionNegativeExponent places after decimal point.

Pow returns 0 (zero-value of Decimal) instead of error for power operation edge cases, to handle those edge cases use PowWithPrecision Edge cases not handled by Pow:

  • 0 ** 0 => undefined value
  • 0 ** y, where y < 0 => infinity
  • x ** y, where x < 0 and y is non-integer decimal => imaginary value

Example: 

d1 := decimal.NewFromFloat(4.0)
d2 := decimal.NewFromFloat(4.0)
res1 := d1.Pow(d2)
res1.String() // output: "256"

d3 := decimal.NewFromFloat(5.0)
d4 := decimal.NewFromFloat(5.73)
res2 := d3.Pow(d4)
res2.String() // output: "10118.08037125"

func (Decimal) PowBigInt added in v1.4.0 

func (d Decimal) PowBigInt(exp *big.Int) (Decimal, error)

PowBigInt returns d to the power of exp, where exp is big.Int. Only returns error when d and exp is 0, thus result is undefined.

When exponent is negative the returned decimal will have maximum precision of PowPrecisionNegativeExponent places after decimal point.

Example: 

d1, err := decimal.NewFromFloat(3.0).PowBigInt(big.NewInt(3))
d1.String() // output: "27"

d2, err := decimal.NewFromFloat(629.25).PowBigInt(big.NewInt(5))
d2.String() // output: "98654323103449.5673828125"

func (Decimal) PowInt32 added in v1.4.0 

func (d Decimal) PowInt32(exp int32) (Decimal, error)

PowInt32 returns d to the power of exp, where exp is int32. Only returns error when d and exp is 0, thus result is undefined.

When exponent is negative the returned decimal will have maximum precision of PowPrecisionNegativeExponent places after decimal point.

Example: 

d1, err := decimal.NewFromFloat(4.0).PowInt32(4)
d1.String() // output: "256"

d2, err := decimal.NewFromFloat(3.13).PowInt32(5)
d2.String() // output: "300.4150512793"

func (Decimal) PowWithPrecision added in v1.4.0 

func (d Decimal) PowWithPrecision(d2 Decimal, precision int32) (Decimal, error)

PowWithPrecision returns d to the power of d2. Precision parameter specifies minimum precision of the result (digits after decimal point). Returned decimal is not rounded to 'precision' places after decimal point.

PowWithPrecision returns error when:

  • 0 ** 0 => undefined value
  • 0 ** y, where y < 0 => infinity
  • x ** y, where x < 0 and y is non-integer decimal => imaginary value

Example: 

d1 := decimal.NewFromFloat(4.0)
d2 := decimal.NewFromFloat(4.0)
res1, err := d1.PowWithPrecision(d2, 2)
res1.String() // output: "256"

d3 := decimal.NewFromFloat(5.0)
d4 := decimal.NewFromFloat(5.73)
res2, err := d3.PowWithPrecision(d4, 5)
res2.String() // output: "10118.080371595015625"

d5 := decimal.NewFromFloat(-3.0)
d6 := decimal.NewFromFloat(-6.0)
res3, err := d5.PowWithPrecision(d6, 10)
res3.String() // output: "0.0013717421"

func (Decimal) QuoRem 

func (d Decimal) QuoRem(d2 Decimal, precision int32) (Decimal, Decimal)

QuoRem does division with remainder d.QuoRem(d2,precision) returns quotient q and remainder r such that 

d = d2 * q + r, q an integer multiple of 10^(-precision)
0 <= r < abs(d2) * 10 ^(-precision) if d>=0
0 >= r > -abs(d2) * 10 ^(-precision) if d<0

Note that precision<0 is allowed as input.

func (Decimal) Rat 

func (d Decimal) Rat() *big.Rat

Rat returns a rational number representation of the decimal.

func (Decimal) Round 

func (d Decimal) Round(places int32) Decimal

Round rounds the decimal to places decimal places. If places < 0, it will round the integer part to the nearest 10^(-places).

Example: 

NewFromFloat(5.45).Round(1).String() // output: "5.5"
NewFromFloat(545).Round(-1).String() // output: "550"

func (Decimal) RoundBank 

func (d Decimal) RoundBank(places int32) Decimal

RoundBank rounds the decimal to places decimal places. If the final digit to round is equidistant from the nearest two integers the rounded value is taken as the even number

If places < 0, it will round the integer part to the nearest 10^(-places).

Examples: 

NewFromFloat(5.45).RoundBank(1).String() // output: "5.4"
NewFromFloat(545).RoundBank(-1).String() // output: "540"
NewFromFloat(5.46).RoundBank(1).String() // output: "5.5"
NewFromFloat(546).RoundBank(-1).String() // output: "550"
NewFromFloat(5.55).RoundBank(1).String() // output: "5.6"
NewFromFloat(555).RoundBank(-1).String() // output: "560"

func (Decimal) RoundCash 

func (d Decimal) RoundCash(interval uint8) Decimal

RoundCash aka Cash/Penny/öre rounding rounds decimal to a specific interval. The amount payable for a cash transaction is rounded to the nearest multiple of the minimum currency unit available. The following intervals are available: 5, 10, 25, 50 and 100; any other number throws a panic. 

  5:   5 cent rounding 3.43 => 3.45
 10:  10 cent rounding 3.45 => 3.50 (5 gets rounded up)
 25:  25 cent rounding 3.41 => 3.50
 50:  50 cent rounding 3.75 => 4.00
100: 100 cent rounding 3.50 => 4.00

For more details: https://en.wikipedia.org/wiki/Cash_rounding

func (Decimal) RoundCeil added in v1.3.0 

func (d Decimal) RoundCeil(places int32) Decimal

RoundCeil rounds the decimal towards +infinity.

Example: 

NewFromFloat(545).RoundCeil(-2).String()   // output: "600"
NewFromFloat(500).RoundCeil(-2).String()   // output: "500"
NewFromFloat(1.1001).RoundCeil(2).String() // output: "1.11"
NewFromFloat(-1.454).RoundCeil(1).String() // output: "-1.4"

func (Decimal) RoundDown added in v1.3.0 

func (d Decimal) RoundDown(places int32) Decimal

RoundDown rounds the decimal towards zero.

Example: 

NewFromFloat(545).RoundDown(-2).String()   // output: "500"
NewFromFloat(-500).RoundDown(-2).String()   // output: "-500"
NewFromFloat(1.1001).RoundDown(2).String() // output: "1.1"
NewFromFloat(-1.454).RoundDown(1).String() // output: "-1.4"

func (Decimal) RoundFloor added in v1.3.0 

func (d Decimal) RoundFloor(places int32) Decimal

RoundFloor rounds the decimal towards -infinity.

Example: 

NewFromFloat(545).RoundFloor(-2).String()   // output: "500"
NewFromFloat(-500).RoundFloor(-2).String()   // output: "-500"
NewFromFloat(1.1001).RoundFloor(2).String() // output: "1.1"
NewFromFloat(-1.454).RoundFloor(1).String() // output: "-1.5"

func (Decimal) RoundUp added in v1.3.0 

func (d Decimal) RoundUp(places int32) Decimal

RoundUp rounds the decimal away from zero.

Example: 

NewFromFloat(545).RoundUp(-2).String()   // output: "600"
NewFromFloat(500).RoundUp(-2).String()   // output: "500"
NewFromFloat(1.1001).RoundUp(2).String() // output: "1.11"
NewFromFloat(-1.454).RoundUp(1).String() // output: "-1.5"

func (*Decimal) Scan 

func (d *Decimal) Scan(value interface{}) error

Scan implements the sql.Scanner interface for database deserialization.

func (Decimal) Shift added in v1.1.0 

func (d Decimal) Shift(shift int32) Decimal

Shift shifts the decimal in base 10. It shifts left when shift is positive and right if shift is negative. In simpler terms, the given value for shift is added to the exponent of the decimal.

func (Decimal) Sign 

func (d Decimal) Sign() int

Sign returns: 

-1 if d <  0
 0 if d == 0
+1 if d >  0

func (Decimal) Sin added in v1.1.0 

func (d Decimal) Sin() Decimal

Sin returns the sine of the radian argument x.

func (Decimal) String 

func (d Decimal) String() string

String returns the string representation of the decimal with the fixed point.

Example: 

d := New(-12345, -3)
println(d.String())

Output: 

-12.345

func (Decimal) StringFixed 

func (d Decimal) StringFixed(places int32) string

StringFixed returns a rounded fixed-point string with places digits after the decimal point.

Example: 

NewFromFloat(0).StringFixed(2) // output: "0.00"
NewFromFloat(0).StringFixed(0) // output: "0"
NewFromFloat(5.45).StringFixed(0) // output: "5"
NewFromFloat(5.45).StringFixed(1) // output: "5.5"
NewFromFloat(5.45).StringFixed(2) // output: "5.45"
NewFromFloat(5.45).StringFixed(3) // output: "5.450"
NewFromFloat(545).StringFixed(-1) // output: "550"

func (Decimal) StringFixedBank 

func (d Decimal) StringFixedBank(places int32) string

StringFixedBank returns a banker rounded fixed-point string with places digits after the decimal point.

Example: 

NewFromFloat(0).StringFixedBank(2) // output: "0.00"
NewFromFloat(0).StringFixedBank(0) // output: "0"
NewFromFloat(5.45).StringFixedBank(0) // output: "5"
NewFromFloat(5.45).StringFixedBank(1) // output: "5.4"
NewFromFloat(5.45).StringFixedBank(2) // output: "5.45"
NewFromFloat(5.45).StringFixedBank(3) // output: "5.450"
NewFromFloat(545).StringFixedBank(-1) // output: "540"

func (Decimal) StringFixedCash 

func (d Decimal) StringFixedCash(interval uint8) string

StringFixedCash returns a Swedish/Cash rounded fixed-point string. For more details see the documentation at function RoundCash.

func (Decimal) StringScaled deprecated 

func (d Decimal) StringScaled(exp int32) string

StringScaled first scales the decimal then calls .String() on it.

Deprecated: buggy and unintuitive. Use StringFixed instead.

func (Decimal) Sub 

func (d Decimal) Sub(d2 Decimal) Decimal

Sub returns d - d2.

func (Decimal) Tan added in v1.1.0 

func (d Decimal) Tan() Decimal

Tan returns the tangent of the radian argument x.

func (Decimal) Truncate 

func (d Decimal) Truncate(precision int32) Decimal

Truncate truncates off digits from the number, without rounding.

NOTE: precision is the last digit that will not be truncated (must be >= 0).

Example: 

decimal.NewFromString("123.456").Truncate(2).String() // "123.45"

func (*Decimal) UnmarshalBinary 

func (d *Decimal) UnmarshalBinary(data []byte) error

UnmarshalBinary implements the encoding.BinaryUnmarshaler interface. As a string representation is already used when encoding to text, this method stores that string as []byte

func (*Decimal) UnmarshalJSON 

func (d *Decimal) UnmarshalJSON(decimalBytes []byte) error

UnmarshalJSON implements the json.Unmarshaler interface.

func (*Decimal) UnmarshalText 

func (d *Decimal) UnmarshalText(text []byte) error

UnmarshalText implements the encoding.TextUnmarshaler interface for XML deserialization.

func (Decimal) Value 

func (d Decimal) Value() (driver.Value, error)

Value implements the driver.Valuer interface for database serialization.

type NullDecimal 

type NullDecimal struct {
	Decimal Decimal
	Valid   bool
}

NullDecimal represents a nullable decimal with compatibility for scanning null values from the database.

func NewNullDecimal added in v1.3.0 

func NewNullDecimal(d Decimal) NullDecimal

func (NullDecimal) MarshalJSON 

func (d NullDecimal) MarshalJSON() ([]byte, error)

MarshalJSON implements the json.Marshaler interface.

func (NullDecimal) MarshalText added in v1.3.0 

func (d NullDecimal) MarshalText() (text []byte, err error)

MarshalText implements the encoding.TextMarshaler interface for XML serialization.

func (*NullDecimal) Scan 

func (d *NullDecimal) Scan(value interface{}) error

Scan implements the sql.Scanner interface for database deserialization.

func (*NullDecimal) UnmarshalJSON 

func (d *NullDecimal) UnmarshalJSON(decimalBytes []byte) error

UnmarshalJSON implements the json.Unmarshaler interface.

func (*NullDecimal) UnmarshalText added in v1.3.0 

func (d *NullDecimal) UnmarshalText(text []byte) error

UnmarshalText implements the encoding.TextUnmarshaler interface for XML deserialization

func (NullDecimal) Value 

func (d NullDecimal) Value() (driver.Value, error)

Value implements the driver.Valuer interface for database serialization.

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