Floating point exponent `pow` returns NaN for integer exponents

[Patrick Pijnappel]

Feel free to close if this is intentional, but currently the floating-point version of pow returns NaN for e.g. Double.pow(-1, 2.0), even though that's not complex. Shouldn't we be checking for Int(exactly: y) != nil? This appears to be the behavior of Darwin.pow(-1, 2.0).

public static func pow(_ x: Double, _ y: Double) -> Double {
    guard x >= 0 else { return .nan }
    return libm_pow(x, y)
}

[Xiaodi Wu]

This behavior is deliberate. See these links:

• https://forums.swift.org/t/rejection-of-negative-bases-bug-or-deliberate-design/32082
• https://github.com/apple/swift-evolution/blob/master/proposals/0246-mathable.md
• #82

[Patrick Pijnappel]

@xwu Ah great that's what I was looking for. Makes sense, thank you.