// Copyright (C) 2010  Davis E. King (davis@dlib.net)
#undef DLIB_MR_FUNCTION_ObJECTS_ABSTRACT_Hh_
#ifdef DLIB_MR_FUNCTION_ObJECTS_ABSTRACT_Hh_

#include "../matrix.h"
#include <cmath>
#include "../svm/sparse_vector_abstract.h"

namespace dlib
{

// ----------------------------------------------------------------------------------------

struct squared_euclidean_distance
{
/*!
WHAT THIS OBJECT REPRESENTS
This is a simple function object that computes squared euclidean distance
between two dlib::matrix objects.

This object has no mutable members.  Therefore, it is safe to call
operator() on a single instance of this object simultaneously from multiple
!*/

squared_euclidean_distance (
);
/*!
ensures
- #lower == 0
- #upper == std::numeric_limits<double>::infinity()
!*/

squared_euclidean_distance (
const double l,
const double u
);
/*!
ensures
- #lower == l
- #upper == u
!*/

const double lower;
const double upper;

template <typename sample_type>
double operator() (
const sample_type& a,
const sample_type& b
) const;
/*!
requires
- sample_type should be a kind of dlib::matrix
ensures
- let LEN = length_squared(a-b)
- if (lower <= LEN <= upper) then
- returns LEN
- else
- returns std::numeric_limits<double>::infinity()
!*/
};

// ----------------------------------------------------------------------------------------

struct cosine_distance
{
/*!
WHAT THIS OBJECT REPRESENTS
This is a simple function object that computes the cosine of the angle
between two vectors and returns 1 - this quantity.   Moreover, this object
works for both sparse and dense vectors.

This object has no mutable members.  Therefore, it is safe to call
operator() on a single instance of this object simultaneously from multiple
!*/

template <typename sample_type>
double operator() (
const sample_type& a,
const sample_type& b
) const;
/*!
requires
- sample_type is a dense vector (e.g. a dlib::matrix) or a sparse
vector as defined at the top of dlib/svm/sparse_vector_abstract.h
ensures
- let theta = the angle between a and b.
- returns 1 - cos(theta)
(e.g. this function returns 0 when a and b have an angle of 0 between
each other, 1 if they have a 90 degree angle, and a maximum of 2 if the
vectors have a 180 degree angle between each other).
- zero length vectors are considered to have angles of 0 between all other
vectors.
!*/
};

// ----------------------------------------------------------------------------------------

struct negative_dot_product_distance
{
/*!
WHAT THIS OBJECT REPRESENTS
This is a simple function object that computes the dot product between two
vectors and returns the negation of this value.  Moreover, this object
works for both sparse and dense vectors.

This object has no mutable members.  Therefore, it is safe to call
operator() on a single instance of this object simultaneously from multiple
!*/

template <typename sample_type>
double operator() (
const sample_type& a,
const sample_type& b
) const;
/*!
requires
- sample_type is a dense vector (e.g. a dlib::matrix) or a sparse
vector as defined at the top of dlib/svm/sparse_vector_abstract.h
ensures
- returns -dot(a,b)
!*/
};

// ----------------------------------------------------------------------------------------

struct use_weights_of_one
{
/*!
WHAT THIS OBJECT REPRESENTS
This is a simple function object that takes a single argument
and always returns 1

This object has no mutable members.  Therefore, it is safe to call
operator() on a single instance of this object simultaneously from multiple
!*/

template <typename edge_type>
double operator() (
const edge_type&
) const;
/*!
ensures
- returns 1
!*/
};

// ----------------------------------------------------------------------------------------

struct use_gaussian_weights
{
/*!
WHAT THIS OBJECT REPRESENTS
This is a simple function object that takes a single argument
which should be an object similar to dlib::sample_pair.

This object has no mutable members.  Therefore, it is safe to call
operator() on a single instance of this object simultaneously from multiple
!*/

use_gaussian_weights (
);
/*!
ensures
- #gamma == 0.1
!*/

use_gaussian_weights (
double g
);
/*!
ensures
- #gamma == g
!*/

double gamma;

template <typename edge_type>
double operator() (
const edge_type& e
) const;
/*!
requires
- e.distance() must be a valid expression that returns a number
(e.g. edge_type might be dlib::sample_pair)
ensures
- returns std::exp(-gamma*e.distance());
!*/
};

// ----------------------------------------------------------------------------------------

}

#endif // DLIB_MR_FUNCTION_ObJECTS_ABSTRACT_Hh_