func (d Dec) Sign() int {
	return d.coef.Sign()
}
Sign returns:

-1 if d <  0
0 if d == 0
+1 if d >  0
package decimal
import (
	"bytes"
	"database/sql/driver"
	"errors"
	"io"
	"math"
	"strconv"
	"strings"
)
type Dec struct {
	coef  Int128
	scale uint8
}
func New(n int64) *Dec {
	d := new(Dec)
	d.SetInt64(n)
	return d
}
var decOne = New(1)
func (d *Dec) Set(x *Dec) *Dec {
	if d != x {
		d.coef = x.coef
		d.scale = x.scale
	}
	return d
}
func (d *Dec) SetInt128(x *Int128) *Dec {
	d.scale = 0
	d.coef = *x
	return d
}