Python-style exponentiation with the ** operator.

Exponentiation.swift

infix operator **: MultiplicationPrecedence

public func **<T: UnsignedInteger>(base: T, exponent: T) -> T {
  return pow(base, exponent)
}

/// Implements pow() for integers using exponentiation by squaring
public func pow<T: BinaryInteger, U: UnsignedInteger>(_ base: T, _ exponent: U) -> T {
  var result: T = 1

  // copy the parameters using .init(T) in case either happens to use a reference type
  var base = T(base)
  var exponent = U(exponent)

  while true {
    if exponent % 2 == 1 {
      result *= base
    }
    exponent >>= 1
    if exponent == 0 { break }
    base *= base
  }
  return result
}

#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)

import Darwin

public func **(base: Double, exponent: Double) -> Double {
  return pow(base, exponent)
}

public func **(base: Float, exponent: Float) -> Float {
  return powf(base, exponent)
}

#endif

Would this work for both cases?

func **<T>(lhs: T, rhs: T) -> T {
    return pow(lhs, rhs)
}

pow is a C function provided by Darwin that's only implemented for double