C++ Boost

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Concepts

All constructs in GIL are models of GIL concepts. A concept is a set of requirements that a type (or a set of related types) must fulfill to be used correctly in generic algorithms. The requirements include syntactic and algorithmic guarantees. For example, GIL class pixel is a model of GIL PixelConcept. The user may substitute the pixel class with one of their own, and, as long as it satisfies the requirements of PixelConcept, all other GIL classes and algorithms can be used with it. See more about concepts at Generic Programming in ConceptC++

In this document we will use a syntax for defining concepts that is described in the C++ standard proposal paper [N2081] Concepts.

Here are some common concepts that will be used in GIL. Most of them are defined at the ConceptC++ Concept Web:

auto concept DefaultConstructible<typename T>
{
    T::T();
};

auto concept CopyConstructible<typename T>
{
    T::T(T);
    T::~T();
};

auto concept Assignable<typename T, typename U = T>
{
    typename result_type;
    result_type operator=(T&, U);
};

auto concept EqualityComparable<typename T, typename U = T>
{
    bool operator==(T x, U y);
    bool operator!=(T x, U y) { return !(x==y); }
};

concept SameType<typename T, typename U> { /* unspecified */ };
template<typename T> concept_map SameType<T, T> { /* unspecified */ };

auto concept Swappable<typename T>
{
    void swap(T& t, T& u);
};

Here are some additional basic concepts that GIL needs:

auto concept Regular<typename T> :
    DefaultConstructible<T>,
    CopyConstructible<T>,
    EqualityComparable<T>,
    Assignable<T>,
    Swappable<T>
{};

auto concept Metafunction<typename T>
{
    typename type;
};
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