forked from boostorg/algorithm
51 lines
1.1 KiB
C++
51 lines
1.1 KiB
C++
/*
|
|
Copyright (c) Marshall Clow 2014.
|
|
|
|
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
|
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
|
|
|
|
Revision history:
|
|
2 Dec 2014 mtc First version; power
|
|
|
|
*/
|
|
|
|
/// \file algorithm.hpp
|
|
/// \brief Misc Algorithms
|
|
/// \author Marshall Clow
|
|
///
|
|
|
|
#ifndef BOOST_ALGORITHM_HPP
|
|
#define BOOST_ALGORITHM_HPP
|
|
|
|
#include <boost/utility/enable_if.hpp> // for boost::disable_if
|
|
|
|
namespace boost { namespace algorithm {
|
|
|
|
/// \fn power ( T x, Integer n )
|
|
/// \return the value "x" raised to the power "n"
|
|
///
|
|
/// \param x The value to be exponentiated
|
|
/// \param n The exponent
|
|
///
|
|
// \remark Taken from Knuth, The Art of Computer Programming, Volume 2:
|
|
// Seminumerical Algorithms, Section 4.6.3
|
|
template <typename T, typename Integer>
|
|
T power (T x, Integer n) {
|
|
T y = 1; // Should be "T y{1};"
|
|
if (n == 0) return y;
|
|
while (true) {
|
|
if (n % 2 == 1) {
|
|
y = x * y;
|
|
if (n == 1)
|
|
return y;
|
|
}
|
|
n = n / 2;
|
|
x = x * x;
|
|
}
|
|
return y;
|
|
}
|
|
|
|
}}
|
|
|
|
#endif // BOOST_ALGORITHM_HPP
|