1 files changed, 120 insertions, 0 deletions
diff --git a/nfa/src/default/nfa.rs b/nfa/src/default/nfa.rs
new file mode 100644
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+++ b/nfa/src/default/nfa.rs
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+//! This file provides a default implementation of NFA.
+
+// TODO: Store the regular expression in the NFA as well.
+//
+// The current focus of the project is to understand the growth rate
+// of the algorithm, to know whether I made a mistake in the previous
+// iteration of the implementation, or the algorithm is not as fast as
+// the author estimated, which is not quite likely, of course.
+//
+// Thus I shall establish a friendly interface that allows me to view
+// and debug the atomic languages and the languages, transparently.
+
+use graph::{error::Error as GError, DLGraph, Graph, GraphLabel, LabelGraph};
+
+use crate::{error::Error, Nfa, Regex};
+
+use std::fmt::Display;
+
+#[non_exhaustive]
+#[derive(Debug)]
+/// Default NFA implementation.
+pub struct DefaultNFA<T: GraphLabel + Display> {
+    graph: DLGraph<T>,
+}
+
+impl<T: GraphLabel + Display> Default for DefaultNFA<T> {
+    fn default() -> Self {
+        Self {
+            graph: Default::default(),
+        }
+    }
+}
+
+impl<T: GraphLabel + Display> Graph for DefaultNFA<T> {
+    type Iter<'a> = <DLGraph<T> as Graph>::Iter<'a> where T: 'a;
+
+    #[inline]
+    fn is_empty(&self) -> bool {
+        self.graph.is_empty()
+    }
+
+    #[inline]
+    fn nodes_len(&self) -> usize {
+        self.graph.nodes_len()
+    }
+
+    #[inline]
+    fn children_of(&self, node_id: usize) -> Result<Self::Iter<'_>, GError> {
+        self.graph.children_of(node_id)
+    }
+
+    #[inline]
+    fn degree(&self, node_id: usize) -> Result<usize, GError> {
+        self.graph.degree(node_id)
+    }
+
+    #[inline]
+    fn is_empty_node(&self, node_id: usize) -> Result<bool, GError> {
+        self.graph.is_empty_node(node_id)
+    }
+
+    #[inline]
+    fn has_edge(&self, source: usize, target: usize) -> Result<bool, GError> {
+        self.graph.has_edge(source, target)
+    }
+}
+
+impl<T: GraphLabel + Display> LabelGraph<T> for DefaultNFA<T> {
+    type Iter<'a> = <DLGraph<T> as LabelGraph<T>>::Iter<'a> where T: 'a;
+
+    type LabelIter<'a> = <DLGraph<T> as LabelGraph<T>>::LabelIter<'a> where T: 'a;
+
+    // TODO: Return the label from the contained regular language.
+    #[inline]
+    fn vertex_label(&self, node_id: usize) -> Result<Option<T>, GError> {
+        if self.has_node(node_id) {
+            todo!()
+        } else {
+            Err(GError::IndexOutOfBounds(node_id, self.nodes_len()))
+        }
+    }
+
+    #[inline]
+    fn edge_label(&self, source: usize, target: usize) -> Result<Vec<T>, GError> {
+        self.graph.edge_label(source, target)
+    }
+
+    #[inline]
+    fn find_children_with_label(
+        &self,
+        node_id: usize,
+        label: &T,
+    ) -> Result<<Self as LabelGraph<T>>::Iter<'_>, GError> {
+        self.graph.find_children_with_label(node_id, label)
+    }
+
+    #[inline]
+    fn labels_of(&self, node_id: usize) -> Result<Self::LabelIter<'_>, GError> {
+        self.graph.labels_of(node_id)
+    }
+}
+
+impl<T: GraphLabel + Display> Nfa<T> for DefaultNFA<T> {
+    #[allow(unused)]
+    fn to_nfa(regex: impl Regex<T>) -> Self {
+        todo!()
+    }
+
+    fn remove_epsilon(&mut self) -> Result<(), Error> {
+        todo!()
+    }
+
+    fn remove_dead(&mut self) -> Result<(), Error> {
+        todo!()
+    }
+
+    fn nulling(&mut self) -> Result<(), Error> {
+        todo!()
+    }
+}