PkXwmpgN/snape

C++ design

Snape

Contents

• Acyclic visitor

Acyclic visitor

An implementation of the acyclic visitor pattern without RTTI

Usage

// class hierarchy

struct entity : snape::visitable<entity>
{
public:

    SNAPE_VISITABLE(entity);

    // something
};

struct geometry : entity
{
public:

    SNAPE_VISITABLE(geometry);

    // something      
};

struct model : entity
{
public:

    SNAPE_VISITABLE(model);

    // something      
};

// visitor
template<typename _Visitor>
using visitor_entities = snape::visitor<_Visitor, snape::visitor_traits<entity>>;

struct visitor : visitor_entities<visitor>
{
public:

    SNAPE_VISIT(entity, geometry, model);

public:

    void visit(const entity & obj)
    {
        // something
    }

    void visit(const geometry & obj)
    {
        // something
    }

    void visit(const model & obj)
    {
        // something
    }
};

// usage
std::vector<entity*> entities =
{
    new entity,
    new model,
    new entity,
    new geometry,
    new entity,
    new model
};

visitor test_visitor;
for(const auto & obj : entities)
    test_visitor(*obj);

Performance

Iterate of three million items

Pattern	Performance(ms)
Cyclic visitor	11.3
Acyclic visitor(RTTI)	220.4
Snape's acyclic visitor	23.2

Acknowledgments

Thanks a lot to Manu Sánchez, for the CTTI