fix: support negative base with integer exponent in Pow#40
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Pow(-2, 3) previously panicked with "Pow: negative base", even though (-2)^3 = -8 is well-defined. This matches the behavior of math.Pow from the standard library. Now handles negative base when the exponent is an integer by computing |z|^w and negating the result for odd exponents. Still panics for negative base with non-integer exponent (which would require complex numbers). Fixes ALTree#35
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Fixes #35
Problem
Pow(z, w)panics for any negativez, even whenwis an integer — a case where the result is well-defined:This is inconsistent with
math.Pow(-2, 3) == -8from the standard library.Fix
For negative base with integer exponent, compute
|z|^wand negate the result for odd exponents:Still panics for negative base with non-integer exponent (which would require complex numbers).
All existing tests pass.