norm.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_NORM_HPP
#define SIG_UTIL_NORM_HPP

#include "comparable_check.hpp"
#include "../calculation/binary_operation.hpp"

#include <numeric>
#undef max
#undef min

namespace sig
{

template <size_t P>
struct Norm
{
    template <class C>
    double operator()(C const& vec) const
    {
        using T = typename impl::container_traits<C>::value_type;

        return std::pow(
            std::accumulate(std::begin(vec), std::end(vec), static_cast<T>(0), [&](T sum, T val){ return sum + std::pow(std::abs(val), P); }),
            1.0 / P
        );
    }
    
    template <class C1, class C2>
    double operator()(C1 const& vec1, C2 const& vec2) const
    {
        assert(is_comparable(vec1, vec2, impl::NumericVectorTag()));
        return this->operator()(minus(vec1, vec2));
    }
};


const Norm<1> norm_L1;


const Norm<2> norm_L2;


struct MaxNorm
{
    template <class C>
    double operator()(C const& vec) const
    {
        using T = typename impl::container_traits<C>::value_type;

        T max = *std::begin(vec);
        for(auto e : vec){
            if(std::abs(e) > max) max = std::abs(e);
        }
        return max;
    }

    template <class C1, class C2>
    double operator()(C1 const& vec1, C2 const& vec2) const
    {
        assert(is_comparable(vec1, vec2, impl::NumericVectorTag()));
        return this->operator()(minus(vec1, vec2));
    }
};


const MaxNorm norm_max;
}
#endif