.. _cpp-compare:

**********************************************************
compare.hpp
**********************************************************

Full path: ``graph_canon/compare.hpp``

.. default-domain:: cpp
.. default-role:: cpp:expr

.. cpp:namespace:: graph_canon

.. function:: template<typename GraphL, typename IndexMapL, bool WithInEdgesL, \
                 typename GraphR, typename IndexMapR, bool WithInEdgesR, \
                 typename VertexEqual, typename EdgeEqual, \
                 typename Visitor> \
              bool ordered_graph_equal( \
                 const ordered_graph<GraphL, IndexMapL, WithInEdgesL> &g_left, \
                 const ordered_graph<GraphR, IndexMapR, WithInEdgesR> &g_right, \
                 VertexEqual vertex_equal, EdgeEqual edge_equal, Visitor &&visitor)

    Compare two ordered graphs for equality.
    For labelled graphs the two binary predicates `vertex_equal` and `edge_equal`,
    can be used to compare labels.
    If the two graphs are not equal the reason is indicated by calling a corresponding
    member function on `visitor`.
    See `graph_compare_null_visitor` for the list of member functions that must exist.

.. function:: template<typename GraphL, typename IndexMapL, bool WithInEdgesL, \
                 typename GraphR, typename IndexMapR, bool WithInEdgesR, \
                 typename VertexLess, typename EdgeLess, \
                 typename VertexEqual, typename EdgeEqual> \
              bool ordered_graph_less( \
                 const ordered_graph<GraphL, IndexMapL, WithInEdgesL> &g_left, \
                 const ordered_graph<GraphR, IndexMapR, WithInEdgesR> &g_right, \
                 VertexLess vertex_less, EdgeLess edge_less, \
                 VertexEqual vertex_equal, EdgeEqual edge_equal)

    Compare two ordered graphs and return `true` when `g_left` is considered smaller than `g_right`.
    For labelled graphs the binary predicates `vertex_less`, `edge_less`, `vertex_equal`, and `edge_equal`,
    can be used to compare labels. The ``_equal`` and ``_less`` versions must be consistent with each other.

.. class:: graph_compare_null_visitor

    A visitor class that can be used for `ordered_graph_equal`.

    .. function:: void at_num_vertices() const

        Called when the two graphs have different number of vertices.
    .. function:: template<typename VertexL, typename VertexR> \
                  void at_vertex_compare(VertexL, VertexR) const 

        Called when the user-defined vertex predicate returns `false` for two vertices with the same index.
    .. function:: template<typename VertexL, typename VertexR> \
                  void at_out_degree(VertexL, VertexR) const 

        Called when two verices with the same index have different out-degrees.
    .. function:: template<typename EdgeL, typename EdgeR> \
                  void at_out_edge(EdgeL, EdgeR) const

        Called when two edges :math:`(u_l, v_l)`, :math:`(u_r, v_r)` from the two graphs, with :math:`u_l` and :math:`u_r` have the same index,
        the edges are in the same position in their respective out-edge lists, but :math:`v_l` and :math:`v_r` have different index.
    .. function:: template<typename EdgeL, typename EdgeR> \
                  void at_edge_compare(EdgeL, EdgeR) const

        Called when two edges :math:`(u_l, v_l)`, :math:`(u_r, v_r)` from the two graphs, with :math:`u_l` and :math:`u_r` have the same index,
        the edges are in the same position in their respective out-edge lists, :math:`v_l` and :math:`v_r` have the same index,
        but the user-defined predicate returns `false`.