L2.h

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//
// Copyright (c) 2009, Markus Rickert
// All rights reserved.
//
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// modification, are permitted provided that the following conditions are met:
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//   this list of conditions and the following disclaimer.
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#ifndef RL_MATH_METRICS_L2_H
#define RL_MATH_METRICS_L2_H
 
namespace rl
{
    namespace math
    {
        namespace metrics
        {
            template<typename T>
            struct L2
            {
                typedef typename T::value_type Distance;
                
                typedef typename T::size_type Size;
                
                typedef T Value;
                
                Distance operator()(const Value& lhs, const Value& rhs) const
                {
                    using ::std::begin;
                    using ::std::end;
                    
                    auto first1 = begin(lhs);
                    auto last1 = end(lhs);
                    auto first2 = begin(rhs);
                    
                    Distance distance = Distance();
                    
                    while (first1 != last1)
                    {
                        Distance tmp = *first1 - *first2;
                        distance += tmp * tmp;
                        ++first1;
                        ++first2;
                    }
                    
                    return ::std::sqrt(distance);
                }
                
                Distance operator()(const Distance& lhs, const Distance& rhs, const Size& index) const
                {
                    return ::std::abs(lhs - rhs);
                }
            };
            
            template<typename Scalar, int Rows, int Options, int MaxRows, int MaxCols>
            struct L2< ::Eigen::Matrix<Scalar, Rows, 1, Options, MaxRows, MaxCols>>
            {
                typedef Scalar Distance;
                
                typedef int Size;
                
                typedef ::Eigen::Matrix<Scalar, Rows, 1, Options, MaxRows, MaxCols> Value;
                
                Distance operator()(const Value& lhs, const Value& rhs) const
                {
                    return (lhs - rhs).norm();
                }
                
                Distance operator()(const Distance& lhs, const Distance& rhs, const Size& index) const
                {
                    return ::std::abs(lhs - rhs);
                }
            };
            
            template<typename Scalar, int Rows, int Options, int MaxRows, int MaxCols>
            struct L2< ::Eigen::Matrix<Scalar, Rows, 1, Options, MaxRows, MaxCols>*>
            {
                typedef Scalar Distance;
                
                typedef int Size;
                
                typedef ::Eigen::Matrix<Scalar, Rows, 1, Options, MaxRows, MaxCols>* Value;
                
                Distance operator()(const Value& lhs, const Value& rhs) const
                {
                    return (*lhs - *rhs).norm();
                }
                
                Distance operator()(const Distance& lhs, const Distance& rhs, const Size& index) const
                {
                    return ::std::abs(lhs - rhs);
                }
            };
            
            template<typename Scalar, int Rows, int Options, int MaxRows, int MaxCols>
            struct L2<const ::Eigen::Matrix<Scalar, Rows, 1, Options, MaxRows, MaxCols>*>
            {
                typedef Scalar Distance;
                
                typedef int Size;
                
                typedef const ::Eigen::Matrix<Scalar, Rows, 1, Options, MaxRows, MaxCols>* Value;
                
                Distance operator()(const Value& lhs, const Value& rhs) const
                {
                    return (*lhs - *rhs).norm();
                }
                
                Distance operator()(const Distance& lhs, const Distance& rhs, const Size& index) const
                {
                    return ::std::abs(lhs - rhs);
                }
            };
        }
    }
}
 
#endif // RL_MATH_METRICS_L2_H