#ifndef __PCSVM_KERNEL__
#define __PCSVM_KERNEL__

#include <cmath>
#include "Vector.hpp"

class KernelI
{
    public:
        virtual float operator()(const Vector&, const Vector&) const = 0;
        virtual float operator()(const SparseVector&, const SparseVector& ) const = 0;
        virtual bool isLinear() const = 0;
};


class LinearKernel: public KernelI
{
    public:
        virtual float operator() (const Vector &v1, const Vector &v2) const {return v1*v2; } 
        virtual float operator() (const SparseVector &v1, const SparseVector &v2) const {return v1*v2; } 
        virtual bool isLinear() const { return true; }
};

class PolynomialKernel: public KernelI
{
    float c_;
    int   d_;

    public:
        PolynomialKernel(float c=1.0f, int d=2): c_(c), d_(d) { };
        virtual float operator()(const Vector &v1, const Vector &v2) const  {return std::pow(1.0 + c_* v1*v2, d_);}
        virtual float operator()(const SparseVector &v1, const SparseVector &v2) const  {return std::pow(1.0 + c_* v1*v2, d_);}
        virtual bool isLinear() const { return false; }
};

template <class V>
class RadialKernel // : public KernelI
{
    float gamma_;

    public:
        RadialKernel(float gamma): gamma_(gamma) { };
        virtual float operator()(const V &v1, const V &v2) {return std::exp(-gamma_* euk_distance(v1,v2)); }
        virtual bool isLinear() const { return false; }
};


#endif