math.go

package main

import "github.com/cockroachdb/apd/v2"

type Dec struct {
	dec apd.Decimal
}

var dec128Context = apd.Context{
	Precision:   34,
	MaxExponent: apd.MaxExponent,
	MinExponent: apd.MinExponent,
	Traps:       apd.DefaultTraps,
}

func NewDecFromString(s string) (Dec, error) {
	d, _, err := apd.NewFromString(s)
	if err != nil {
		return Dec{}, err
	}
	return Dec{*d}, nil
}

func NewDecFromInt64(x int64) Dec {
	var res Dec
	res.dec.SetInt64(x)
	return res
}

func (x Dec) Add(y Dec) (Dec, error) {
	var z Dec
	_, err := apd.BaseContext.Add(&z.dec, &x.dec, &y.dec)
	return z, err
}

func (x Dec) Sub(y Dec) (Dec, error) {
	var z Dec
	_, err := apd.BaseContext.Sub(&z.dec, &x.dec, &y.dec)
	return z, err
}

func (x Dec) Quo(y Dec) (Dec, error) {
	var z Dec
	_, err := dec128Context.Quo(&z.dec, &x.dec, &y.dec)
	return z, err
}

func (x Dec) QuoInteger(y Dec) (Dec, error) {
	var z Dec
	_, err := dec128Context.QuoInteger(&z.dec, &x.dec, &y.dec)
	return z, err
}

func (x Dec) Rem(y Dec) (Dec, error) {
	var z Dec
	_, err := dec128Context.Rem(&z.dec, &x.dec, &y.dec)
	return z, err
}

func (x Dec) Mul(y Dec) (Dec, error) {
	var z Dec
	_, err := dec128Context.Mul(&z.dec, &x.dec, &y.dec)
	return z, err
}

func (x Dec) Int64() (int64, error) {
	return x.dec.Int64()
}

func (x Dec) String() string {
	return x.dec.Text('f')
}

func (x Dec) IsEqual(y Dec) bool {
	return x.dec.Cmp(&y.dec) == 0
}

func (x Dec) IsZero() bool {
	return x.dec.IsZero()
}

func (x Dec) IsPositive() bool {
	return !x.dec.Negative && !x.dec.IsZero()
}

func (x Dec) IsNegative() bool {
	return x.dec.Negative && !x.dec.IsZero()
}