diff --git a/Cargo.toml b/Cargo.toml
index 2c83773..7c11125 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "purrchance"
-version = "0.3.0"
+version = "0.4.0"
 authors = ["xenofem <xenofem@xeno.science>"]
 description = "An unofficial Rust implementation of the Perchance grammar engine"
 repository = "https://git.xeno.science/xenofem/purrchance"
diff --git a/src/lib.rs b/src/lib.rs
index 9dd40a6..36bb7ec 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -10,7 +10,7 @@ pub trait Purrchance {
     fn eval(&self, g: &Grammar) -> Option<String>;
 }
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub enum Symbol {
     Terminal(String),
     NonTerminal(String),
@@ -25,7 +25,7 @@ impl Purrchance for Symbol {
     }
 }
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct Expr(Vec<Symbol>);
 
 impl Purrchance for Expr {
@@ -34,7 +34,7 @@ impl Purrchance for Expr {
     }
 }
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct List(Vec<(Expr, f64)>);
 
 impl Purrchance for List {
@@ -43,7 +43,7 @@ impl Purrchance for List {
     }
 }
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct Grammar(HashMap<String,List>);
 
 #[cfg(test)]