Add crate doc front-page, and update readme

src/lib.rs

@@ -1,3 +1,132 @@
+//! Graph models and algorithms.
+//!
+//! This crate provides data structures to model graphs and to perform algorithms on these data
+//! structures. The functionality presented is designed to be easy to use, flexible, and performant.
+//!
+//! Currently supported are:
+//!
+//! * Undirected graph types [`Graph`] and [`AppendGraph`] built on a flat, index-based adjacency
+//! list,
+//! * [`VertexMap`] and [`EdgeMap`] to freely associate custom data with vertices and edges,
+//! * Connectivity and pathing algorithms: [Dijkstra's algorithm], [DFS], and [BFS] in different
+//! variants,
+//! * Exposed traits to implement custom graph data structures or algorithms.
+//!
+//! # Usage example
+//!
+//! This example demonstrates some of this library's features.
+//!
+//! ```
+//! // Brings commonly used traits into scope.
+//! use grapherity::prelude::*;
+//! use grapherity::models::Graph;
+//! use grapherity::algorithms;
+//!
+//! let mut graph = Graph::new();
+//! // Creates a map for edge weights with a default weight.
+//! let mut weights = graph.edge_map(1);
+//! // Adds three vertices and two edges.
+//! let v1 = graph.add_vertex();
+//! let v2 = graph.add_vertex();
+//! let v3 = graph.add_vertex();
+//! graph.add_edge(v1, v2);
+//! let e = graph.add_edge(v2, v3);
+//! // Sets a non-default weight for the second edge.
+//! weights[e] = 5;
+//!
+//! // Checks the number of vertices.
+//! assert_eq!(graph.vertex_count(), 3);
+//! // Checks the number of edges.
+//! assert_eq!(graph.edge_count(), 2);
+//! // Checks that v1 and v2 are adjacent.
+//! assert!(graph.are_adjacent(v1, v2));
+//! // Checks that v1 and v3 are not adjacent.
+//! assert!(!graph.are_adjacent(v1, v3));
+//! // Checks the sum of all vertex degrees.
+//! let sum: usize = graph.vertices().map(|v| graph.degree(v)).sum();
+//! assert_eq!(sum, 1 + 2 + 1);
+//!
+//! // Calls Dijkstra's algorithm using the edge weights to find the shortest path from v1 to v3.
+//! let result = algorithms::dijkstra(&graph, v1, |e| weights[e]);
+//! assert_eq!(result.distances[v3], Some(1 + 5));
+//! assert_eq!(result.predecessors[v3], Some(v2));
+//!
+//! // Deletes the middle vertex and its incident edges.
+//! graph.delete_vertex(v2);
+//!
+//! // Calls Dijkstra's algorithm again on the now disconnected graph.
+//! let result = algorithms::dijkstra(&graph, v1, |e| weights[e]);
+//! assert_eq!(result.distances[v3], None);
+//! assert_eq!(result.predecessors[v3], None);
+//! ```
+//!
+//! # Graph types
+//!
+//! [`Graph`] and [`AppendGraph`] both implement [`GraphTopology`] using a flat, index-based adjacency
+//! list to store edges, which means that vertex and edge insertions happen in `O(1)`. Degree
+//! lookups are also `O(1)`.
+//!
+//! [`Graph`] additionally implements [`GraphTopologyDeletion`], thereby supporting deletion of
+//! vertices and edges.
+//!
+//! [`AppendGraph`] does not support deletion, vertices and edges can only be added, allowing it to
+//! be smaller and more performant compared to [`Graph`] by not requiring the per-element generation
+//! tracking needed for stable handles after deletion.
+//!
+//! # Vertices and edges
+//!
+//! Graphs in this library use stable indices [`GraphTopology::Vertex`] and [`GraphTopology::Edge`]
+//! to denote vertices and edges. This means that vertices and edges returned by graph functions
+//! never change, even if the underlying graph data structure is mutated. However, vertices and
+//! edges can become invalid when the denoted element is deleted. Code using an invalid vertex or
+//! edge in a graph method will panic.
+//!
+//! ```should_panic
+//! # use grapherity::prelude::*;
+//! # use grapherity::models::Graph;
+//! let mut graph = Graph::new();
+//! let v = graph.add_vertex();
+//! graph.delete_vertex(v);
+//! // This will panic because 'v' was deleted and is not valid anymore.
+//! graph.degree(v);
+//! ```
+//!
+//! [`VertexMap`] and [`EdgeMap`] are not required to panic if provided with an invalid
+//! vertex or edge.
+//!
+//! Vertices and edges are provided by the graph and not intended to be generated by users.
+//!
+//! # Loops and multi-edges
+//!
+//! Loops and multi edges are supported as well. In the following example, `v1` will have two loops
+//! and two edges to `v2`.
+//!
+//! ```
+//! # use grapherity::prelude::*;
+//! # use grapherity::models::Graph;
+//! let mut graph = Graph::new();
+//! let v1 = graph.add_vertex();
+//! let v2 = graph.add_vertex();
+//! for _ in 0..2 {
+//!     graph.add_edge(v1, v1);
+//!     graph.add_edge(v1, v2);
+//! }
+//! assert_eq!(graph.edge_count(), 4);
+//! assert_eq!(graph.degree(v1), 6);
+//! ```
+//!
+//! [BFS]: crate::algorithms::bfs
+//! [Dijkstra's algorithm]: crate::algorithms::dijkstra
+//! [DFS]: crate::algorithms::dfs
+//! [`EdgeMap`]: crate::maps::EdgeMap
+//! [`VertexMap`]: crate::maps::VertexMap
+//! [`AppendGraph`]: crate::models::AppendGraph
+//! [`Graph`]: crate::models::Graph
+//! [`GraphTopology`]: crate::traits::GraphTopology
+//! [`GraphTopology::Edge`]: crate::traits::GraphTopology::Edge
+//! [`GraphTopology::Vertex`]: crate::traits::GraphTopology::Vertex
+//! [`GraphTopologyDeletion`]: crate::traits::GraphTopologyDeletion
+
 #![warn(missing_docs)]
 
 pub mod algorithms;