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fix: support negative base with integer exponent in Pow #40

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fix: support negative base with integer exponent in Pow #40

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17 changes: 15 additions & 2 deletions pow.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,11 +3,24 @@ package bigfloat
import "math/big"

// Pow returns a big.Float representation of z**w. Precision is the same as the one
// of the first argument. The function panics when z is negative.
// of the first argument. The function panics when z is negative and w is
// not an integer.
func Pow(z *big.Float, w *big.Float) *big.Float {

if z.Sign() < 0 {
panic("Pow: negative base")
// For negative base, handle integer exponents: (-z)^n = (-1)^n * z^n
if w.IsInt() {
// Compute |z|^w
abs := new(big.Float).Abs(z)
result := Pow(abs, w)
// If exponent is odd, negate the result
wInt, _ := w.Int(nil)
if wInt.Bit(0) == 1 { // odd
result.Neg(result)
}
return result
}
panic("Pow: negative base with non-integer exponent")
}

// Pow(z, 0) = 1.0
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