diff --git a/sl/src/lib.rs b/sl/src/lib.rs
index 4b1d45b..a31b2ad 100644
--- a/sl/src/lib.rs
+++ b/sl/src/lib.rs
@@ -26,6 +26,8 @@ pub enum Prim {
     Add,
     Sub,
     Mul,
+    Div,
+    Mod,
     Eq,
     Cons,
     Car,
@@ -136,6 +138,8 @@ impl Env {
                 ("+", Rc::new(Form::Prim(Prim::Add))),
                 ("-", Rc::new(Form::Prim(Prim::Sub))),
                 ("*", Rc::new(Form::Prim(Prim::Mul))),
+                ("/", Rc::new(Form::Prim(Prim::Div))),
+                ("%", Rc::new(Form::Prim(Prim::Mod))),
                 ("cons", Rc::new(Form::Prim(Prim::Cons))),
                 ("cdr", Rc::new(Form::Prim(Prim::Cdr))),
                 ("car", Rc::new(Form::Prim(Prim::Car))),
@@ -250,6 +254,8 @@ pub fn tree_walker_eval(f: Rc<Form>, e: Rc<RefCell<Env>>) -> Result<Rc<Form>> {
                                         Prim::Add => Form::new_int(a.int()? + b.int()?),
                                         Prim::Sub => Form::new_int(a.int()? - b.int()?),
                                         Prim::Mul => Form::new_int(a.int()? * b.int()?),
+                                        Prim::Div => Form::new_int(a.int()? / b.int()?),
+                                        Prim::Mod => Form::new_int(a.int()? % b.int()?),
                                         Prim::Cons => Form::new_pair(a, b),
                                         Prim::Eq  => Form::new_bool(a.my_eq(&b)),
                                         _ => unreachable!(),
@@ -314,6 +320,8 @@ impl fmt::Display for Form {
                     Prim::Add => write!(f, "+"),
                     Prim::Sub => write!(f, "-"),
                     Prim::Mul => write!(f, "*"),
+                    Prim::Div => write!(f, "/"),
+                    Prim::Mod => write!(f, "%"),
                     Prim::Cons => write!(f, "cons"),
                     Prim::Car => write!(f, "car"),
                     Prim::Cdr => write!(f, "cdr"),