Golang Rat.Sign方法代码示例

func (r BigRat) floatString(verb byte, prec int) string {
	switch verb {
	case 'f', 'F':
		return r.Rat.FloatString(prec)
	case 'e', 'E':
		// The exponent will alway be >= 0.
		sign := ""
		var x, t big.Rat
		x.Set(r.Rat)
		if x.Sign() < 0 {
			sign = "-"
			x.Neg(&x)
		}
		t.Set(&x)
		exp := ratExponent(&x)
		ratScale(&t, exp)
		str := t.FloatString(prec + 1) // +1 because first digit might be zero.
		// Drop the decimal.
		if str[0] == '0' {
			str = str[2:]
			exp--
		} else if len(str) > 1 && str[1] == '.' {
			str = str[0:1] + str[2:]
		}
		return eFormat(verb, prec, sign, str, exp)
	case 'g', 'G':
		var x big.Rat
		x.Set(r.Rat)
		exp := ratExponent(&x)
		// Exponent could be positive or negative
		if exp < -4 || prec <= exp {
			// Use e format.
			verb -= 2 // g becomes e.
			return trimEZeros(verb, r.floatString(verb, prec-1))
		}
		// Use f format.
		// If it's got zeros right of the decimal, they count as digits in the precision.
		// If it's got digits left of the decimal, they count as digits in the precision.
		// Both are handled by adjusting prec by exp.
		str := r.floatString(verb-1, prec-exp-1) // -1 for the one digit left of the decimal.
		// Trim trailing decimals.
		point := strings.IndexByte(str, '.')
		if point > 0 {
			n := len(str)
			for str[n-1] == '0' {
				n--
			}
			str = str[:n]
			if str[n-1] == '.' {
				str = str[:n-1]
			}
		}
		return str
	default:
		Errorf("can't handle verb %c for rational", verb)
	}
	return ""
}

// MulRat returns a new Currency value c = x * y, where y is a big.Rat.
func (x Currency) MulRat(y *big.Rat) (c Currency) {
	if y.Sign() < 0 {
		build.Critical(ErrNegativeCurrency)
	} else {
		c.i.Mul(&x.i, y.Num())
		c.i.Div(&c.i, y.Denom())
	}
	return
}

// MulRat returns a new Currency value c = x * y, where y is a big.Rat.
func (x Currency) MulRat(y *big.Rat) (c Currency) {
	if y.Sign() < 0 {
		if build.DEBUG {
			panic(ErrNegativeCurrency)
		}
	} else {
		c.i.Mul(&x.i, y.Num())
		c.i.Div(&c.i, y.Denom())
	}
	return
}

// Takes a transaction and balances it. This is mainly to fill in the empty part
// with the remaining balance.
func balanceTransaction(input *Transaction) error {
	balance := new(big.Rat)
	var emptyAccPtr *Account
	var emptyAccIndex int
	for accIndex, accChange := range input.AccountChanges {
		if accChange.Balance == nil {
			if emptyAccPtr != nil {
				return fmt.Errorf("More than one account change empty!")
			}
			emptyAccPtr = &accChange
			emptyAccIndex = accIndex
		} else {
			balance = balance.Add(balance, accChange.Balance)
		}
	}
	if balance.Sign() != 0 {
		if emptyAccPtr == nil {
			return fmt.Errorf("No empty account change to place extra balance!")
		}
		input.AccountChanges[emptyAccIndex].Balance = balance.Neg(balance)
	}
	return nil
}

// ratExponent returns the power of ten that x would display in scientific notation.
func ratExponent(x *big.Rat) int {
	if x.Sign() < 0 {
		x.Neg(x)
	}
	e := 0
	invert := false
	if x.Num().Cmp(x.Denom()) < 0 {
		invert = true
		x.Inv(x)
		e++
	}
	for x.Cmp(bigRatBillion) >= 0 {
		e += 9
		x.Quo(x, bigRatBillion)
	}
	for x.Cmp(bigRatTen) > 0 {
		e++
		x.Quo(x, bigRatTen)
	}
	if invert {
		return -e
	}
	return e
}

// newComplex returns the smallest constant representation
// for the specific value re + im*i; either an int64, *big.Int,
// *big.Rat, or complex value.
//
func newComplex(re, im *big.Rat) interface{} {
	if im.Sign() == 0 {
		return normalizeRatConst(re)
	}
	return Complex{re, im}
}

func normComplex(re, im *big.Rat) Value {
	if im.Sign() == 0 {
		return normFloat(re)
	}
	return complexVal{re, im}
}