206 lines
6.2 KiB
Go
206 lines
6.2 KiB
Go
package types
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import (
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"math/big"
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"strconv"
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"strings"
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)
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// "that's one big rat!"
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// ______
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// / / /\ \____oo
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// __ /___...._____ _\o
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// __| |_ |_
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// Rat - extend big.Rat
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type Rat struct {
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*big.Rat `json:"rat"`
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}
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// Rational - big Rat with additional functionality
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type Rational interface {
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GetRat() *big.Rat
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Num() int64
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Denom() int64
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GT(Rational) bool
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LT(Rational) bool
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Equal(Rational) bool
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IsZero() bool
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Inv() Rational
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Mul(Rational) Rational
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Quo(Rational) Rational
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Add(Rational) Rational
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Sub(Rational) Rational
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Round(int64) Rational
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Evaluate() int64
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}
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var _ Rational = Rat{} // enforce at compile time
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// nolint - common values
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var (
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ZeroRat = Rat{big.NewRat(0, 1)}
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OneRat = Rat{big.NewRat(1, 1)}
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)
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// New - create a new Rat from integers
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func NewRat(Numerator int64, Denominator ...int64) Rat {
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switch len(Denominator) {
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case 0:
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return Rat{big.NewRat(Numerator, 1)}
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case 1:
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return Rat{big.NewRat(Numerator, Denominator[0])}
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default:
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panic("improper use of New, can only have one denominator")
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}
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}
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//NewFromDecimal - create a rational from decimal string or integer string
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func NewRatFromDecimal(decimalStr string) (f Rat, err Error) {
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// first extract any negative symbol
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neg := false
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if string(decimalStr[0]) == "-" {
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neg = true
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decimalStr = decimalStr[1:]
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}
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str := strings.Split(decimalStr, ".")
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var numStr string
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var denom int64 = 1
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switch len(str) {
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case 1:
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if len(str[0]) == 0 {
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return f, NewError(CodeUnknownRequest, "not a decimal string")
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}
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numStr = str[0]
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case 2:
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if len(str[0]) == 0 || len(str[1]) == 0 {
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return f, NewError(CodeUnknownRequest, "not a decimal string")
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}
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numStr = str[0] + str[1]
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len := int64(len(str[1]))
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denom = new(big.Int).Exp(big.NewInt(10), big.NewInt(len), nil).Int64()
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default:
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return f, NewError(CodeUnknownRequest, "not a decimal string")
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}
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num, errConv := strconv.Atoi(numStr)
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if errConv != nil {
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return f, NewError(CodeUnknownRequest, errConv.Error())
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}
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if neg {
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num *= -1
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}
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return Rat{big.NewRat(int64(num), denom)}, nil
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}
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//nolint
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func (r Rat) GetRat() *big.Rat { return r.Rat } // GetRat - get big.Rat
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func (r Rat) Num() int64 { return r.Rat.Num().Int64() } // Num - return the numerator
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func (r Rat) Denom() int64 { return r.Rat.Denom().Int64() } // Denom - return the denominator
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func (r Rat) IsZero() bool { return r.Num() == 0 } // IsZero - Is the Rat equal to zero
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func (r Rat) Equal(r2 Rational) bool { return r.Rat.Cmp(r2.GetRat()) == 0 } // Equal - rationals are equal
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func (r Rat) GT(r2 Rational) bool { return r.Rat.Cmp(r2.GetRat()) == 1 } // GT - greater than
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func (r Rat) LT(r2 Rational) bool { return r.Rat.Cmp(r2.GetRat()) == -1 } // LT - less than
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func (r Rat) Inv() Rational { return Rat{new(big.Rat).Inv(r.Rat)} } // Inv - inverse
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func (r Rat) Mul(r2 Rational) Rational { return Rat{new(big.Rat).Mul(r.Rat, r2.GetRat())} } // Mul - multiplication
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func (r Rat) Quo(r2 Rational) Rational { return Rat{new(big.Rat).Quo(r.Rat, r2.GetRat())} } // Quo - quotient
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func (r Rat) Add(r2 Rational) Rational { return Rat{new(big.Rat).Add(r.Rat, r2.GetRat())} } // Add - addition
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func (r Rat) Sub(r2 Rational) Rational { return Rat{new(big.Rat).Sub(r.Rat, r2.GetRat())} } // Sub - subtraction
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var zero = big.NewInt(0)
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var one = big.NewInt(1)
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var two = big.NewInt(2)
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var five = big.NewInt(5)
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var nFive = big.NewInt(-5)
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var ten = big.NewInt(10)
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// EvaluateBig - evaluate the rational using bankers rounding
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func (r Rat) EvaluateBig() *big.Int {
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num := r.Rat.Num()
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denom := r.Rat.Denom()
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d, rem := new(big.Int), new(big.Int)
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d.QuoRem(num, denom, rem)
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if rem.Cmp(zero) == 0 { // is the remainder zero
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return d
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}
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// evaluate the remainder using bankers rounding
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tenNum := new(big.Int).Mul(num, ten)
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tenD := new(big.Int).Mul(d, ten)
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remainderDigit := new(big.Int).Sub(new(big.Int).Quo(tenNum, denom), tenD) // get the first remainder digit
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isFinalDigit := (new(big.Int).Rem(tenNum, denom).Cmp(zero) == 0) // is this the final digit in the remainder?
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switch {
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case isFinalDigit && (remainderDigit.Cmp(five) == 0 || remainderDigit.Cmp(nFive) == 0):
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dRem2 := new(big.Int).Rem(d, two)
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return new(big.Int).Add(d, dRem2) // always rounds to the even number
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case remainderDigit.Cmp(five) != -1: //remainderDigit >= 5:
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d.Add(d, one)
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case remainderDigit.Cmp(nFive) != 1: //remainderDigit <= -5:
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d.Sub(d, one)
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}
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return d
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}
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// Evaluate - evaluate the rational using bankers rounding
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func (r Rat) Evaluate() int64 {
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return r.EvaluateBig().Int64()
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}
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// Round - round Rat with the provided precisionFactor
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func (r Rat) Round(precisionFactor int64) Rational {
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rTen := Rat{new(big.Rat).Mul(r.Rat, big.NewRat(precisionFactor, 1))}
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return Rat{big.NewRat(rTen.Evaluate(), precisionFactor)}
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}
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//___________________________________________________________________________________
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//var ratCdc = RegisterWire(wire.NewCodec())
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//// add rational codec elements to provided codec
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//func RegisterWire(cdc *wire.Codec) *wire.Codec {
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//cdc.RegisterInterface((*Rational)(nil), nil)
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//cdc.RegisterConcrete(Rat{}, "rat", nil)
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//return cdc
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//}
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//TODO there has got to be a better way using native MarshalText and UnmarshalText
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// RatMarshal - Marshable Rat Struct
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//type RatMarshal struct {
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//Numerator int64 `json:"numerator"`
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//Denominator int64 `json:"denominator"`
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//}
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//// MarshalJSON - custom implementation of JSON Marshal
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//func (r Rat) MarshalJSON() ([]byte, error) {
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//return ratCdc.MarshalJSON(RatMarshal{r.Num(), r.Denom()})
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//}
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//// UnmarshalJSON - custom implementation of JSON Unmarshal
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//func (r *Rat) UnmarshalJSON(data []byte) (err error) {
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//defer func() {
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//if rcv := recover(); rcv != nil {
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//err = fmt.Errorf("Panic during UnmarshalJSON: %v", rcv)
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//}
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//}()
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//ratMar := new(RatMarshal)
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//if err := ratCdc.UnmarshalJSON(data, ratMar); err != nil {
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//return err
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//}
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//r.Rat = big.NewRat(ratMar.Numerator, ratMar.Denominator)
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//return nil
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//}
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//nolint
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func (r Rat) MarshalJSON() ([]byte, error) { return r.MarshalText() }
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func (r *Rat) UnmarshalJSON(data []byte) (err error) { return r.UnmarshalText(data) }
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