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#![warn(missing_docs)]
//! This file implements a data type that implements the trait
//! [`Graph`][super::Graph]. This data type represents graphs using
//! adjacency sets internally.
//!
//! I need this because the derivatives languages should not allow
//! duplications of languages, so it is more convenient if the
//! underlying graph type **cannot** represent duplicate edges.
use super::{ExtGraph, Graph};
use crate::error::Error;
// If one wants to use another implementation for a set, import that
// as Set, and nothing else needs to be changed, ideally.
use std::collections::{hash_set::Iter, HashSet as Set};
#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
struct ASEdge {
to: usize,
}
impl ASEdge {
fn new(to: usize) -> Self {
Self { to }
}
}
#[derive(Debug, Clone, Default)]
struct ASNode {
children: Set<ASEdge>,
}
impl ASNode {
fn new(children: Set<ASEdge>) -> Self {
Self { children }
}
}
/// The graph implemented using adjacency sets.
#[derive(Debug, Clone, Default)]
pub struct ASGraph {
nodes: Vec<ASNode>,
}
/// A delegation of iterators.
///
/// This is here to avoid using a boxed pointer, in order to save some
/// allocations.
pub struct ASIter<'a> {
iter: Iter<'a, ASEdge>,
}
impl<'a> Iterator for ASIter<'a> {
type Item = usize;
fn next(&mut self) -> Option<Self::Item> {
self.iter.next().map(|edge| edge.to)
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
impl<'a> ExactSizeIterator for ASIter<'a> {
fn len(&self) -> usize {
self.iter.len()
}
}
impl Graph for ASGraph {
type Iter<'a> = ASIter<'a>;
#[inline]
fn is_empty(&self) -> bool {
self.nodes.is_empty()
}
#[inline]
fn nodes_len(&self) -> usize {
self.nodes.len()
}
fn children_of(&self, node_id: usize) -> Result<Self::Iter<'_>, Error> {
match self.nodes.get(node_id) {
Some(node) => {
let iter = node.children.iter();
Ok(Self::Iter { iter })
}
None => Err(Error::IndexOutOfBounds(node_id, self.nodes_len())),
}
}
#[inline]
fn degree(&self, node_id: usize) -> Result<usize, Error> {
match self.nodes.get(node_id) {
Some(node) => Ok(node.children.len()),
None => Err(Error::IndexOutOfBounds(node_id, self.nodes_len())),
}
}
#[inline]
fn is_empty_node(&self, node_id: usize) -> Result<bool, Error> {
match self.nodes.get(node_id) {
Some(node) => Ok(node.children.is_empty()),
None => Err(Error::IndexOutOfBounds(node_id, self.nodes_len())),
}
}
#[inline]
fn has_edge(&self, source: usize, target: usize) -> Result<bool, Error> {
if !self.has_node(source) {
Err(Error::IndexOutOfBounds(source, self.nodes_len()))
} else if !self.has_node(target) {
Err(Error::IndexOutOfBounds(target, self.nodes_len()))
} else {
Ok(self
.nodes
.get(source)
.unwrap()
.children
.contains(&ASEdge::new(target)))
}
}
}
impl ExtGraph for ASGraph {
fn extend(&mut self, edges: impl IntoIterator<Item = usize>) -> Result<usize, Error> {
let mut new_node_children = Set::default();
for edge_to in edges.into_iter() {
if !self.has_node(edge_to) {
return Err(Error::IndexOutOfBounds(edge_to, self.nodes_len()));
}
new_node_children.insert(ASEdge::new(edge_to));
}
let new_node = ASNode::new(new_node_children);
self.nodes.push(new_node);
Ok(self.nodes.len() - 1)
}
}
#[cfg(test)]
mod asgraph_test {
use super::*;
#[test]
fn test_graph_apis() -> Result<(), Error> {
let mut graph = ASGraph::default();
assert!(graph.is_empty());
graph.extend(std::iter::empty())?;
graph.extend([0].iter().copied())?;
graph.extend([0, 1].iter().copied())?;
graph.extend([0, 2].iter().copied())?;
graph.extend([1, 2].iter().copied())?;
graph.extend([1, 2, 3].iter().copied())?;
let graph = graph;
assert_eq!(graph.nodes_len(), 6);
assert_eq!(graph.children_of(5)?.collect::<Set<_>>(), {
let mut set = Set::default();
set.insert(1);
set.insert(3);
set.insert(2);
set
});
assert_eq!(graph.degree(4)?, 2);
assert!(graph.is_empty_node(0)?);
assert!(!graph.is_empty_node(1)?);
assert!(graph.has_edge(3, 2)?);
assert!(!graph.has_edge(3, 1)?);
assert_eq!(graph.has_edge(3, 6), Err(Error::IndexOutOfBounds(6, 6)));
Ok(())
}
#[test]
fn test_extending_algraph_normal() -> Result<(), Error> {
let mut graph = ASGraph::default();
let new = graph.extend(std::iter::empty())?;
println!("new index = {new}");
println!("new graph = {graph:?}");
let new = graph.extend([0].iter().copied())?;
println!("new index = {new}");
println!("new graph = {graph:?}");
let new = graph.extend([0, 1].iter().copied())?;
println!("new index = {new}");
println!("new graph = {graph:?}");
Ok(())
}
#[test]
fn test_extending_algraph_error() -> Result<(), Error> {
let mut graph = ASGraph::default();
graph.extend(std::iter::empty())?;
graph.extend([0].iter().copied())?;
assert_eq!(
graph.extend([2].iter().copied()),
Err(Error::IndexOutOfBounds(2, 2))
);
Ok(())
}
}
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