1 files changed, 8 insertions, 3 deletions

diff --git a/src/lisp/expr.rs b/src/lisp/expr.rs
index 94e778f..4676a3e 100644
--- a/src/lisp/expr.rs
+++ b/src/lisp/expr.rs
@@ -1,14 +1,17 @@
 use std::fmt;
 
-use crate::lisp::number::LispNumber;
+use crate::app::AppState;
+use crate::lisp::{error::LispError, number::LispNumber};
 
-#[derive(Debug, PartialEq, Clone)]
+#[derive(Clone)]
 pub enum LispExpr {
+    Unit,
     Number(LispNumber),
     List(Vec<LispExpr>),
     StringLit(String),
     BoolLit(bool),
     Ident(String),
+    PrimitiveFunc(fn(&[LispExpr], Option<&mut AppState>) -> Result<LispExpr, LispError>),
     Function(LispFunction),
 
     // none of these depths should be zero
@@ -56,6 +59,7 @@ impl LispExpr {
 impl fmt::Display for LispExpr {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
+            LispExpr::Unit => write!(f, "()")?,
             LispExpr::Number(n) => write!(f, "{}", n)?,
             LispExpr::List(l) => {
                 for expr in l.iter() {
@@ -71,6 +75,7 @@ impl fmt::Display for LispExpr {
                 }
             }
             LispExpr::Ident(s) => write!(f, "{}", s)?,
+            LispExpr::PrimitiveFunc(_) => write!(f, "<#primitive>")?,
             LispExpr::Function(_) => write!(f, "<#procedure>")?,
             LispExpr::Quasiquote(val, depth) => {
                 write!(f, "{}{}", "`".repeat(*depth as usize), val)?
@@ -84,4 +89,4 @@ impl fmt::Display for LispExpr {
 }
 
 #[derive(Debug, PartialEq, Clone)]
-struct LispFunction {}
+enum LispFunction {}