# `hawick_circuits`

    template <typename Graph, typename Visitor, typename VertexIndexMap>
    void hawick_circuits(Graph const& graph, Visitor visitor, VertexIndexMap const& vim = get(vertex_index, graph), unsigned int max_length = 0);

    template <typename Graph, typename Visitor, typename VertexIndexMap>
    void hawick_unique_circuits(Graph const& graph, Visitor visitor, VertexIndexMap const& vim = get(vertex_index, graph), unsigned int max_length = 0);

Enumerate all the elementary circuits (of length ≤ `max_length`, if nonzero) in a directed multigraph. Specifically, self-loops and redundant circuits caused by parallel edges are enumerated too. `hawick_unique_circuits` may be used if redundant circuits caused by parallel edges are not desired.

The algorithm is described in detail in https://www.researchgate.net/publication/221440635_Enumerating_Circuits_and_Loops_in_Graphs_with_Self-Arcs_and_Multiple-Arcs.

### Where defined

`#include <boost/graph/hawick_circuits.hpp>`

### Parameters

IN: `Graph const& graph`

> The graph on which the algorithm is to be performed. It must be a model of the `VertexListGraph` and `AdjacencyGraph` concepts.

IN: `Visitor visitor`

> The visitor that will be notified on each circuit found by the algorithm. The `visitor.cycle(circuit, graph)` expression must be valid, with `circuit` being a `const`-reference to a random access sequence of `vertex_descriptor`s.

> For example, if a circuit `u -> v -> w -> u` exists in the graph, the visitor will be called with a sequence consisting of `(u, v, w)`.

IN: `VertexIndexMap const& vim = get(vertex_index, graph)`

> A model of the `ReadablePropertyMap` concept mapping each `vertex_descriptor` to an integer in the range `[0, num_vertices(graph))`. It defaults to using the vertex index map provided by the `graph`.

IN: `unsigned int max_length = 0`

> The maximum circuit length to consider. Beyond this it truncates the depth-first search, reducing the computation time by ignoring longer circuits. The default value of `max_length = 0` implies no maximum.