WIP: working on test graph traits and stuck on lifetimes

.gitignore

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+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "graph-rs"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "graph-rs"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

src/edge.rs

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+pub trait Edge {}

src/graph.rs

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+use crate::edge::Edge;
+use crate::vertex::Vertex;
+
+/// operations you might want to do on a graph or on nodes in a graph
+pub trait Graph<V: Vertex, E: Edge> {
+    // Connect two nodes, and return the edge
+    // TODO: figure out a way to modify self? is that even needed?
+    // same for `disconnect()`
+    fn connect(vertex_1: &V, vertex_2: &V) -> E;
+
+    // disconnect two nodes, and return the old edge
+    fn disconnect(vertex_1: &V, vertex_2: &V) -> E;
+
+    // get the degree of a given vertex - possibly put this in a GraphUtil trait?
+    fn degree(vertex: V) -> usize;
+}

src/lib.rs

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+mod edge;
+mod graph;
+mod vertex;
+
+#[cfg(test)]
+mod test;

src/test.rs

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+use std::marker::PhantomData;
+
+use crate::{edge::Edge, graph::Graph, vertex::Vertex};
+
+struct TestEdge<'a> {
+    v1: &'a TestVertex<'a>,
+    v2: &'a TestVertex<'a>,
+}
+
+impl<'a> Edge for TestEdge<'a> {}
+
+struct TestVertex<'a> {
+    _phantom: PhantomData<&'a Self>,
+}
+
+impl<'a> Vertex for TestVertex<'a> {}
+
+struct TestGraph<'a> {
+    vertices: Vec<TestVertex<'a>>,
+    edges: Vec<TestEdge<'a>>,
+}
+
+impl<'a> TestGraph<'a> {
+    pub fn get_vertex(&self, index: usize) -> &TestVertex {
+        assert!(index < self.vertices.len());
+        &self.vertices[index]
+    }
+}
+
+impl<'a> Graph<TestVertex<'a>, TestEdge<'a>> for TestGraph<'a> {
+    fn connect(vertex_1: &TestVertex<'a>, vertex_2: &TestVertex<'a>) -> TestEdge<'a> {
+        TestEdge {
+            v1: vertex_1,
+            v2: vertex_2,
+        }
+    }
+
+    fn disconnect(vertex_1: &TestVertex, vertex_2: &TestVertex) -> TestEdge<'a> {
+        todo!();
+    }
+
+    fn degree(vertex: TestVertex) -> usize {
+        todo!();
+    }
+}
+
+#[test]
+fn it_works() {}
+
+#[test]
+fn test_connect() {
+    let v1 = TestVertex {};
+    let v2 = TestVertex {};
+    let mut g = TestGraph {
+        vertices: vec![v1, v2],
+        edges: Vec::new(),
+    };
+
+    let v1 = g.get_vertex(0);
+    let v2 = g.get_vertex(1);
+    // TODO: because g is immutable borrowed above, the trait can't have a &mut self here, which leads to this
+    // not so great syntax. but maybe that's OK because since this is a trait library, we don't care about the
+    // overall implementation, and the graph class might not store the edge... but it does still feel like
+    // the graph has changed... but idk.
+    let e: TestEdge = TestGraph::connect(v1, v2);
+}
+
+#[test]
+fn test_disconnect() {
+    todo!();
+}
+
+#[test]
+fn test_degree() {
+    todo!()
+}

src/vertex.rs

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+pub trait Vertex {}