distance_concept.h

// Description: Distance concept
// Documentation: distances.txt

#ifndef PASTELMATH_DISTANCE_CONCEPT_H
#define PASTELMATH_DISTANCE_CONCEPT_H

#include "pastel/sys/mytypes.h"

namespace Pastel
{

    struct Distance_Native {};

    template <typename T>
    concept Distance_Concept_ =
        requires(T t, typename T::Real_ s) {
            //! Constructs a zero distance.
            T();

            //! Copy-constructs from a given distance.
            T(addConst(t));

            //! Move-constructs from a given distance.
            T(std::move(t));

            //! Assigns from another distance.
            t = addConst(t);

            //! Constructs a distance with the given value.
            /*!
           There may be many distances which correspond to
           the same value; this will pick one of them. 
           An example of multiple equal distances is the 
           product-distance.
           */
            T(s);

            //! Returns the distance.
            (typename T::Real_)addConst(t);

            //! Multiplies the distance by the given value.
            {t *= s} -> std::same_as<T&>;

            //! Divides the distance by the given value.
            /*!
           Deriving from DistanceBase implements this automatically.
           */
            {t /= s} -> std::same_as<T&>;

            //! Distances comparisons.
            /*!
           Deriving from DistanceBase implements these automatically.
           */
            {t < t && t <= t && t > t && t >= t && t == t && t != t} -> std::convertible_to<bool>;

            //! Replace distance along some standard basis axis.
            /*!
           axis:
           The index of the axis to replace.

           from:
           The current distance along the axis.

           to:
           The next distance along the axis.
           */
            {t.replace(
                // axis
                (integer)0,
                // from
                s,
                // to
                s
            )} -> std::same_as<T&>;
        };

    template <typename T>
    concept Distance_Concept =
        Distance_Concept_<RemoveCvRef<T>>;

}

#include "pastel/math/distance/distance_archetype.h"

#endif