...one of the most highly
regarded and expertly designed C++ library projects in the
world.

— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards

`hawick_circuits`

```
template <typename Graph, typename Visitor, typename VertexIndexMap>
void hawick_circuits(Graph const& graph, Visitor visitor, VertexIndexMap const& vim = get(vertex_index, graph));
template <typename Graph, typename Visitor, typename VertexIndexMap>
void hawick_unique_circuits(Graph const& graph, Visitor visitor, VertexIndexMap const& vim = get(vertex_index, graph));
```

Enumerate all the elementary circuits 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.

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

**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`

.