Pow returns d to the power of d2. When exponent is negative the returned decimal will have maximum precision of PowPrecisionNegativeExponent places after decimal point. Pow returns 0 (zero-value of Decimal) instead of error for power operation edge cases, to handle those edge cases use PowWithPreci
(d2 Decimal)
| 696 | // res2 := d3.Pow(d4) |
| 697 | // res2.String() // output: "10118.08037125" |
| 698 | func (d Decimal) Pow(d2 Decimal) Decimal { |
| 699 | baseSign := d.Sign() |
| 700 | expSign := d2.Sign() |
| 701 | |
| 702 | if baseSign == 0 { |
| 703 | if expSign == 0 { |
| 704 | return Decimal{} |
| 705 | } |
| 706 | if expSign == 1 { |
| 707 | return Decimal{zeroInt, 0} |
| 708 | } |
| 709 | if expSign == -1 { |
| 710 | return Decimal{} |
| 711 | } |
| 712 | } |
| 713 | |
| 714 | if expSign == 0 { |
| 715 | return Decimal{oneInt, 0} |
| 716 | } |
| 717 | |
| 718 | // TODO: optimize extraction of fractional part |
| 719 | one := Decimal{oneInt, 0} |
| 720 | expIntPart, expFracPart := d2.QuoRem(one, 0) |
| 721 | |
| 722 | if baseSign == -1 && !expFracPart.IsZero() { |
| 723 | return Decimal{} |
| 724 | } |
| 725 | |
| 726 | intPartPow, _ := d.PowBigInt(expIntPart.value) |
| 727 | |
| 728 | // if exponent is an integer we don't need to calculate d1**frac(d2) |
| 729 | if expFracPart.value.Sign() == 0 { |
| 730 | return intPartPow |
| 731 | } |
| 732 | |
| 733 | // TODO: optimize NumDigits for more performant precision adjustment |
| 734 | digitsBase := d.NumDigits() |
| 735 | digitsExponent := d2.NumDigits() |
| 736 | |
| 737 | precision := digitsBase |
| 738 | |
| 739 | if digitsExponent > precision { |
| 740 | precision += digitsExponent |
| 741 | } |
| 742 | |
| 743 | precision += 6 |
| 744 | |
| 745 | // Calculate x ** frac(y), where |
| 746 | // x ** frac(y) = exp(ln(x ** frac(y)) = exp(ln(x) * frac(y)) |
| 747 | fracPartPow, err := d.Abs().Ln(-d.exp + int32(precision)) |
| 748 | if err != nil { |
| 749 | return Decimal{} |
| 750 | } |
| 751 | |
| 752 | fracPartPow = fracPartPow.Mul(expFracPart) |
| 753 | |
| 754 | fracPartPow, err = fracPartPow.ExpTaylor(-d.exp + int32(precision)) |
| 755 | if err != nil { |