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rational.go
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rational.go
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package types
import (
"fmt"
"math/big"
"strconv"
"strings"
)
// "that's one big rat!"
// ______
// / / /\ \____oo
// __ /___...._____ _\o
// __| |_ |_
// NOTE: never use new(Rat) or else
// we will panic unmarshalling into the
// nil embedded big.Rat
type Rat struct {
big.Rat `json:"rat"`
}
// nolint - common values
func ZeroRat() Rat { return Rat{*big.NewRat(0, 1)} }
func OneRat() Rat { return Rat{*big.NewRat(1, 1)} }
// New - create a new Rat from integers
func NewRat(Numerator int64, Denominator ...int64) Rat {
switch len(Denominator) {
case 0:
return Rat{*big.NewRat(Numerator, 1)}
case 1:
return Rat{*big.NewRat(Numerator, Denominator[0])}
default:
panic("improper use of New, can only have one denominator")
}
}
// create a rational from decimal string or integer string
func NewRatFromDecimal(decimalStr string) (f Rat, err Error) {
// first extract any negative symbol
neg := false
if string(decimalStr[0]) == "-" {
neg = true
decimalStr = decimalStr[1:]
}
str := strings.Split(decimalStr, ".")
var numStr string
var denom int64 = 1
switch len(str) {
case 1:
if len(str[0]) == 0 {
return f, ErrUnknownRequest("not a decimal string")
}
numStr = str[0]
case 2:
if len(str[0]) == 0 || len(str[1]) == 0 {
return f, ErrUnknownRequest("not a decimal string")
}
numStr = str[0] + str[1]
len := int64(len(str[1]))
denom = new(big.Int).Exp(big.NewInt(10), big.NewInt(len), nil).Int64()
default:
return f, ErrUnknownRequest("not a decimal string")
}
num, errConv := strconv.Atoi(numStr)
if errConv != nil {
return f, ErrUnknownRequest(errConv.Error())
}
if neg {
num *= -1
}
return NewRat(int64(num), denom), nil
}
//nolint
func (r Rat) Num() int64 { return r.Rat.Num().Int64() } // Num - return the numerator
func (r Rat) Denom() int64 { return r.Rat.Denom().Int64() } // Denom - return the denominator
func (r Rat) IsZero() bool { return r.Num() == 0 } // IsZero - Is the Rat equal to zero
func (r Rat) Equal(r2 Rat) bool { return (&(r.Rat)).Cmp(&(r2.Rat)) == 0 } // Equal - rationals are equal
func (r Rat) GT(r2 Rat) bool { return (&(r.Rat)).Cmp(&(r2.Rat)) == 1 } // Equal - rationals are equal
func (r Rat) LT(r2 Rat) bool { return (&(r.Rat)).Cmp(&(r2.Rat)) == -1 } // Equal - rationals are equal
func (r Rat) Mul(r2 Rat) Rat { return Rat{*new(big.Rat).Mul(&(r.Rat), &(r2.Rat))} } // Mul - multiplication
func (r Rat) Quo(r2 Rat) Rat { return Rat{*new(big.Rat).Quo(&(r.Rat), &(r2.Rat))} } // Quo - quotient
func (r Rat) Add(r2 Rat) Rat { return Rat{*new(big.Rat).Add(&(r.Rat), &(r2.Rat))} } // Add - addition
func (r Rat) Sub(r2 Rat) Rat { return Rat{*new(big.Rat).Sub(&(r.Rat), &(r2.Rat))} } // Sub - subtraction
func (r Rat) String() string { return fmt.Sprintf("%v/%v", r.Num(), r.Denom()) } // Sub - subtraction
var (
zero = big.NewInt(0)
one = big.NewInt(1)
two = big.NewInt(2)
five = big.NewInt(5)
nFive = big.NewInt(-5)
ten = big.NewInt(10)
)
// evaluate the rational using bankers rounding
func (r Rat) EvaluateBig() *big.Int {
num := r.Rat.Num()
denom := r.Rat.Denom()
d, rem := new(big.Int), new(big.Int)
d.QuoRem(num, denom, rem)
if rem.Cmp(zero) == 0 { // is the remainder zero
return d
}
// evaluate the remainder using bankers rounding
tenNum := new(big.Int).Mul(num, ten)
tenD := new(big.Int).Mul(d, ten)
remainderDigit := new(big.Int).Sub(new(big.Int).Quo(tenNum, denom), tenD) // get the first remainder digit
isFinalDigit := (new(big.Int).Rem(tenNum, denom).Cmp(zero) == 0) // is this the final digit in the remainder?
switch {
case isFinalDigit && (remainderDigit.Cmp(five) == 0 || remainderDigit.Cmp(nFive) == 0):
dRem2 := new(big.Int).Rem(d, two)
return new(big.Int).Add(d, dRem2) // always rounds to the even number
case remainderDigit.Cmp(five) != -1: //remainderDigit >= 5:
d.Add(d, one)
case remainderDigit.Cmp(nFive) != 1: //remainderDigit <= -5:
d.Sub(d, one)
}
return d
}
// evaluate the rational using bankers rounding
func (r Rat) Evaluate() int64 {
return r.EvaluateBig().Int64()
}
// round Rat with the provided precisionFactor
func (r Rat) Round(precisionFactor int64) Rat {
rTen := Rat{*new(big.Rat).Mul(&(r.Rat), big.NewRat(precisionFactor, 1))}
return Rat{*big.NewRat(rTen.Evaluate(), precisionFactor)}
}
// TODO panic if negative or if totalDigits < len(initStr)???
// evaluate as an integer and return left padded string
func (r Rat) ToLeftPadded(totalDigits int8) string {
intStr := r.EvaluateBig().String()
fcode := `%0` + strconv.Itoa(int(totalDigits)) + `s`
return fmt.Sprintf(fcode, intStr)
}
//___________________________________________________________________________________
//Wraps r.MarshalText().
func (r Rat) MarshalAmino() (string, error) {
bz, err := (&(r.Rat)).MarshalText()
return string(bz), err
}
// Requires a valid JSON string - strings quotes and calls UnmarshalText
func (r *Rat) UnmarshalAmino(text string) (err error) {
tempRat := big.NewRat(0, 1)
err = tempRat.UnmarshalText([]byte(text))
if err != nil {
return err
}
r.Rat = *tempRat
return nil
}