.. _cpp-dimacs_graph_io:

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

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

.. cpp:namespace:: graph_canon

.. function:: template<typename Graph> \
              void write_dimacs_graph(std::ostream &s, const Graph &g)

    Write the given graph in DIMACS format (see :cpp:func:`read_dimacs_format`).

    The vertices must have indices, i.e., the expression `get(boost::verex_index_t(), g)` must be valid.
    Currently the expression `get(boost::vertex_name_t(), g)` must also be valid and return a property map with integer values
    If any vertex have non-zero vertex name, then the graph is considered vertex labelled and the vertex names are written.
.. function:: template<typename Graph, typename ParallelHandler, typename LoopHandler> \
              bool read_dimacs_graph(std::istream &s, Graph &graph, std::ostream &err, ParallelHandler parHandler, LoopHandler loopHandler)

    Parse a graph in DIMACS format from `s` and store it in `graph`.
    Reading errors are written to `err`.

    The unary predicate `loopHandler` is called with vertex indices where a loop edge has been parsed.
    The edge is added to the graph only if the handler returns `true`.
    The binary predicate `parHandler` must similarly evaluated parallel edges, if present.

    The format is line-based. Empty lines and lines starting with ``c`` are ignored.
    The first non-ignored line must be on the form ``p edge <n> <m>`` where
    ``<n>`` is the number of vertices in edge graph and
    ``<m>`` is the number of edges.
    Afterwards there must be exactly ``<m>`` lines on the form
    ``e <src> <tar>`` where ``<src>`` and ``<tar>`` are vertex IDs in the range 1 to :math:`n`,
    representing and edge.

    In addition there may be any number of lines on the form ``n <id> <label>``
    where ``<id>`` is a vertex ID in the range 1 to :math:`n`,
    and ``<label>`` is a non-negative number that will be assigned as the label of the vertex.