3 files changed, 4 insertions, 26 deletions
diff --git a/nfa/Cargo.toml b/nfa/Cargo.toml
index 7f48760..9eac932 100644
--- a/nfa/Cargo.toml
+++ b/nfa/Cargo.toml
@@ -7,8 +7,9 @@ edition = "2021"
 
 [dependencies]
 graph = { path = "../graph", optional = true }
-receme = { path = "../receme" }
+receme = { path = "../receme", optional = true }
 
 [features]
 default = ["default-graph"]
 default-graph = ["dep:graph"]
+recursion = ["dep:receme"]
diff --git a/nfa/src/default/regex.rs b/nfa/src/default/regex.rs
index 5e0d53b..1c22687 100644
--- a/nfa/src/default/regex.rs
+++ b/nfa/src/default/regex.rs
@@ -4,6 +4,7 @@ use graph::{error::Error as GError, ALGraph, ExtGraph, Graph, GraphLabel};
 
 use crate::{desrec::DesRec, error::Error, Regex};
 
+#[cfg(feature = "recursion")]
 use receme::{algebra::Algebra, catana::Cata};
 
 use std::{
@@ -193,7 +194,7 @@ impl<T: GraphLabel> DefaultRegex<T> {
     }
 }
 
-// REVIEW: This may not be needed.
+#[cfg(feature = "recursion")]
 impl<S: GraphLabel, T, A> Cata<T, Vec<T>, A> for &DefaultRegex<S>
 where
     A: Algebra<T, Vec<T>>,
diff --git a/nfa/src/lib.rs b/nfa/src/lib.rs
index 07bbd5a..de71f25 100644
--- a/nfa/src/lib.rs
+++ b/nfa/src/lib.rs
@@ -210,17 +210,6 @@ pub trait Nfa<T: GraphLabel>: LabelExtGraph<T> {
     /// different type for the result type.
     type FromRegex<S: GraphLabel + Display + Default>;
 
-    // FIXME: This should not be needed.
-    /// Remove all empty transitions from the nondeterministic finite
-    /// automaton.
-    #[inline]
-    fn remove_epsilon<F>(&mut self, _f: F) -> Result<(), Error>
-    where
-        F: FnMut(T) -> bool,
-    {
-        unimplemented!("deprecated")
-    }
-
     /// Return a state-minimal NFA equivalent with the original one.
     ///
     /// This is not required.  It is just to allow me to experiment
@@ -299,19 +288,6 @@ pub trait Nfa<T: GraphLabel>: LabelExtGraph<T> {
     /// edges.  We can call this "a poor man's removal of nodes".
     fn remove_dead(&mut self, reserve: impl FnMut(usize) -> bool) -> Result<(), Error>;
 
-    // FIXME: This should not be needed.
-    /// For each edge from A to B whose edge is considered nullable by
-    /// a function `f`, and for every edge from B to C, add an edge
-    /// from A to C.
-    ///
-    /// This is needed specifically by the algorithm to produce a set
-    /// of atomic languages that represent "null-closed" derived
-    /// languages.
-    #[inline]
-    fn nulling(&mut self, _f: impl FnMut(T) -> bool) -> Result<(), Error> {
-        unimplemented!("deprecated")
-    }
-
     /// Return the *closure* of the nondeterministic finite automaton.
     ///
     /// # Definition