diff --git a/src/parser.rs b/src/parser.rs
index 07b8088..7cadac4 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -66,7 +66,7 @@ fn stream_of_lexer<'a>(
 mod tests {
     use super::*;
 
-    fn assert_parse(src: &str, expected: &[Value]) {
+    fn assert_parse<'a>(src: &'a str, expected: &'a [Value<'a>]) {
         assert_eq!(read(src).unwrap(), expected)
     }
 
diff --git a/src/value.rs b/src/value.rs
index c1fdd2c..eff25b2 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -3,7 +3,7 @@ use ordered_float::OrderedFloat;
 use std::{
     borrow::Cow,
     collections::BTreeMap,
-    fmt::{Display, Write},
+    fmt::{Debug, Display, Write},
     rc::Rc,
 };
 
@@ -15,6 +15,8 @@ pub enum Value<'a> {
     Map(BTreeMap<Self, Self>),
     Module(Module<'a>),
     Function(Function<'a>),
+    InternalFn(fn(&'a List<'a>) -> Value<'a>),
+    Macro(/* TODO: Bytecode */),
     Symbol(Symbol<'a>),
     Keyword(Cow<'a, str>),
     Bool(bool),
@@ -83,7 +85,9 @@ impl<'a> Display for Value<'a> {
             Value::Module(_) => write!(f, "#module#"),
             Value::Symbol(sym) => write!(f, "{sym}"),
             Value::Keyword(kw) => write!(f, ":{kw}"),
-            Value::Function { .. } => write!(f, "fn"),
+            Value::Function { .. } => write!(f, "#fn#"),
+            Value::InternalFn(function) => write!(f, "#internal-fn@{function:p}"),
+            Value::Macro() => write!(f, "#macro#"),
             Value::Bool(b) => write!(f, "{b}"),
             Value::Number(n) => write!(f, "{n}"),
             Value::String(s) => write!(f, "\"{s}\""),