minkowski_distance.hpp

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/*
Copyright© 2014 Akihiro Nishimura

This software is released under the MIT License.
http://opensource.org/licenses/mit-license.php
*/

#ifndef SIG_UTIL_MINKOWSKI_DISTANCE_HPP
#define SIG_UTIL_MINKOWSKI_DISTANCE_HPP

#include "comparable_check.hpp"

namespace sig
{

template <size_t P>
struct MinkowskiDistance
{
    template <class C1, class C2>
    double operator()(C1 const& vec1, C2 const& vec2) const
    {
        using T = typename std::common_type<typename impl::container_traits<C1>::value_type, typename impl::container_traits<C2>::value_type>::type;
        
        assert(is_comparable(vec1, vec2, impl::NumericVectorTag()));

        return std::pow(
            std::inner_product(std::begin(vec1), std::end(vec1), std::begin(vec2), 0.0, std::plus<double>(), [&](T v1, T v2){ return std::pow(std::abs(v1 - v2), P); }),
            1.0 / P
        );
    }
};

using ManhattanDistance = MinkowskiDistance<1>;


const ManhattanDistance manhattan_distance;


using EuclideanDistance = MinkowskiDistance<2>;

const EuclideanDistance euclidean_distance;

}
#endif