delphi - 如何在 Delphi 中将数字提高到幂？

Question

如何在 Delphi 中将数字提高到幂？

Answer 1

在 Delphi 4 及更高版本中，使用数学单元中的 Power 函数。在早期版本中，使用下面给出的 Pow 函数。

{** A power function from Jack Lyle. Said to be more powerful than the
Pow function that comes with Delphi. }
function Power2(Base, Exponent : Double) : Double;
{ raises the base to the exponent }
CONST
cTiny = 1e-15;

VAR
Power : Double; { Value before sign correction }

BEGIN
Power := 0;
{ Deal with the near zero special cases }
IF (Abs(Base) < cTiny) THEN BEGIN
  Base := 0.0;
END; { IF }
IF (Abs(Exponent) < cTiny) THEN BEGIN
  Exponent := 0.0;
END; { IF }

{ Deal with the exactly zero cases }
IF (Base = 0.0) THEN BEGIN
  Power := 0.0;
END; { IF }
IF (Exponent = 0.0) THEN BEGIN
  Power := 1.0;
END; { IF }

{ Cover everything else }
IF ((Base < 0) AND (Exponent < 0)) THEN
    Power := 1/Exp(-Exponent*Ln(-Base))
ELSE IF ((Base < 0) AND (Exponent >= 0)) THEN
    Power := Exp(Exponent*Ln(-Base))
ELSE IF ((Base > 0) AND (Exponent < 0)) THEN
    Power := 1/Exp(-Exponent*Ln(Base))
ELSE IF ((Base > 0) AND (Exponent >= 0)) THEN
    Power := Exp(Exponent*Ln(Base));

{ Correct the sign }
IF ((Base < 0) AND (Frac(Exponent/2.0) <> 0.0)) THEN
  Result := -Power
ELSE
  Result := Power;
END; { FUNCTION Pow }

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