Add From and FromGraph implementations for Graph and AppendGraph

src/models.rs

@@ -1,5 +1,8 @@
 //! Concrete graph topology models.
 
+use crate::maps::ElementMap;
+use crate::traits::{GraphTopology, GraphTopologyAddition};
+
 pub mod append_graph;
 pub mod frozen_graph;
 pub mod graph;
@@ -11,3 +14,35 @@ pub use frozen_graph::{
     FrozenGraph, FrozenGraphEdgeMap, FrozenGraphIncidence, FrozenGraphVertexMap,
 };
 pub use graph::{Graph, GraphEdgeMap, GraphIncidence, GraphVertexMap};
+
+/// Builds a new graph isomorphic to `source`.
+///
+/// The resulting graph type `G` must implement [`GraphTopologyAddition`] which is used to add
+/// vertices and edges. `on_edge` is called for each edge in `source` together with the
+/// corresponding new edge of the new graph, which callers can use to construct an edge mapping.
+///
+/// Used by the [`GraphTopologyAddition`] models' `From<&H>` and [`FromGraph`] implementations.
+///
+/// [`FromGraph`]: crate::traits::FromGraph
+pub(crate) fn build_from_topology<G: GraphTopologyAddition, H: GraphTopology>(
+    source: &H,
+    vertex_default: G::Vertex,
+    mut on_edge: impl FnMut(H::Edge, G::Edge),
+) -> (G, ElementMap<H::Vertex, G::Vertex>) {
+    let mut result = G::default();
+    result.reserve_vertices(source.vertex_count());
+    result.reserve_edges(source.edge_count());
+
+    let mut vertex_map = source.vertex_map(vertex_default);
+    for v in source.vertices() {
+        vertex_map[v] = result.add_vertex();
+    }
+
+    for e in source.edges() {
+        let (u, v) = source.incident_vertices(e);
+        let new_edge = result.add_edge(vertex_map[u], vertex_map[v]);
+        on_edge(e, new_edge);
+    }
+
+    (result, vertex_map)
+}

src/models/append_graph.rs

@@ -3,7 +3,8 @@
 use std::num::NonZeroUsize;
 
 use crate::maps::ElementMap;
-use crate::traits::{GraphTopology, GraphTopologyAddition, Incidence, IncidenceCursor};
+use crate::models;
+use crate::traits::{FromGraph, GraphTopology, GraphTopologyAddition, Incidence, IncidenceCursor};
 
 /// An opaque handle identifying a vertex in an [`AppendGraph`].
 ///
@@ -259,14 +260,38 @@ impl GraphTopologyAddition for AppendGraph {
     }
 }
 
+impl<H: GraphTopology> From<&H> for AppendGraph {
+    fn from(source: &H) -> Self {
+        models::build_from_topology::<Self, _>(source, Vertex(usize::MAX), |_, _| {}).0
+    }
+}
+
+impl FromGraph for AppendGraph {
+    fn from_graph<H: GraphTopology>(
+        source: &H,
+    ) -> (
+        Self,
+        ElementMap<H::Vertex, Vertex>,
+        ElementMap<H::Edge, Edge>,
+    ) {
+        let mut edge_map = source.edge_map(Edge(NonZeroUsize::MAX));
+        let (result, vertex_map) =
+            models::build_from_topology(source, Vertex(usize::MAX), |e, new_e| edge_map[e] = new_e);
+        (result, vertex_map, edge_map)
+    }
+}
+
 #[cfg(test)]
 mod trait_tests {
     use super::AppendGraph;
+    use crate::models::Graph;
 
     crate::graph_topology_tests!(AppendGraph);
     crate::graph_topology_addition_tests!(AppendGraph);
     crate::graph_topology_clone_tests!(AppendGraph);
     crate::graph_topology_addition_clone_tests!(AppendGraph);
+    crate::graph_topology_from_graph_tests!(AppendGraph, Graph);
+    crate::graph_topology_addition_from_graph_tests!(AppendGraph, Graph);
 }
 
 #[cfg(test)]

src/models/graph.rs

@@ -4,8 +4,10 @@ use std::num::NonZeroUsize;
 use typed_generational_arena::{Arena, Index};
 
 use crate::maps::ElementMap;
+use crate::models;
 use crate::traits::{
-    GraphTopology, GraphTopologyAddition, GraphTopologyDeletion, Incidence, IncidenceCursor,
+    FromGraph, GraphTopology, GraphTopologyAddition, GraphTopologyDeletion, Incidence,
+    IncidenceCursor,
 };
 
 /// An opaque handle identifying a vertex in a [`Graph`].
@@ -398,9 +400,38 @@ impl GraphTopologyDeletion for Graph {
     }
 }
 
+impl<H: GraphTopology> From<&H> for Graph {
+    fn from(source: &H) -> Self {
+        models::build_from_topology::<Self, _>(
+            source,
+            Vertex::new(usize::MAX, usize::MAX),
+            |_, _| {},
+        )
+        .0
+    }
+}
+
+impl FromGraph for Graph {
+    fn from_graph<H: GraphTopology>(
+        source: &H,
+    ) -> (
+        Self,
+        ElementMap<H::Vertex, Vertex>,
+        ElementMap<H::Edge, Edge>,
+    ) {
+        let mut edge_map = source.edge_map(Edge::new(usize::MAX, usize::MAX));
+        let (result, vertex_map) =
+            models::build_from_topology(source, Vertex::new(usize::MAX, usize::MAX), |e, new_e| {
+                edge_map[e] = new_e
+            });
+        (result, vertex_map, edge_map)
+    }
+}
+
 #[cfg(test)]
 mod trait_tests {
     use super::Graph;
+    use crate::models::AppendGraph;
 
     crate::graph_topology_tests!(Graph);
     crate::graph_topology_addition_tests!(Graph);
@@ -408,6 +439,8 @@ mod trait_tests {
     crate::graph_topology_addition_deletion_tests!(Graph);
     crate::graph_topology_clone_tests!(Graph);
     crate::graph_topology_addition_clone_tests!(Graph);
+    crate::graph_topology_from_graph_tests!(Graph, AppendGraph);
+    crate::graph_topology_addition_from_graph_tests!(Graph, AppendGraph);
 }
 
 #[cfg(test)]