mapgraph 0.9.0

A directed graph that can also be used as an arbitrary map.
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# mapgraph

[![crate](https://img.shields.io/crates/v/mapgraph.svg)](https://crates.io/crates/mapgraph)
[![documentation](https://docs.rs/mapgraph/badge.svg)](https://docs.rs/mapgraph)

A powerful library for directed adjacency list graphs.

Graph is a complex data structure where relations between nodes may often be cyclic which
doesn't go well with the Rust's type system. A typical approach to this is to refer to nodes and
edges in a graph using node and edge indices (sometimes called IDs or keys) which are **mapped**
to the actual nodes, edges and their weights instead of using references or pointers. Since
we're **mapping** indices anyway why not make the **maps** we use generic and allow custom
indices?

`mapgraph` provides the generic `Graph` type that is based on two maps: one for nodes and
one for edges. By using the rich system of traits from the `map` submodule the `Graph` type
may borrow some capabilities of the maps it's based on. For example, using a `HashMap` as a
node map for a `Graph` makes it accept external indices for nodes, effectively making the
graph an index for its own nodes.

```rust
use mapgraph::aliases::{SlotMapGraph, HashSlotMapGraph};

// Using a graph with a SlotMap backing its nodes. The node's index is produced internally.
let mut first_graph = SlotMapGraph::<String, ()>::default();
let node_index = first_graph.add_node("foo".to_string());
assert_eq!(first_graph.node_weight(node_index).unwrap(), "foo");

// Using a graph with a HashMap backing its nodes. The node's index is supplied externally.
let mut second_graph = HashSlotMapGraph::<&str, (), &str>::default();
second_graph.try_add_node_at_index("foo", "bar")?;
assert_eq!(second_graph.node_weight("foo").unwrap(), &"bar");
```

See the crate's [documentation](https://docs.rs/mapgraph) for more info.

## License

Licensed under either of

* Apache License, Version 2.0
  ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
* MIT license
  ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)

at your option.

## Contribution

Contributions are welcome and should be submitted as merge requests to this repository.

Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
dual licensed as above, without any additional terms or conditions.