canberra_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_CANBERRA_DISTANCE_HPP
#define SIG_UTIL_CANBERRA_DISTANCE_HPP

#include "../functional/high_order.hpp"
#include "comparable_check.hpp"

namespace sig
{

struct CanberraDistance
{
    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()));
        auto tmp = sig::zipWith([](T val1, T val2){ return static_cast<T>(std::abs(val1 - val2)) / (std::abs(val1) + std::abs(val2)); }, vec1, vec2);

        return std::accumulate(std::begin(tmp), std::end(tmp), T(), std::plus<T>());
    }
};


const CanberraDistance canberra_distance;

}
#endif