diff --git a/crates/erg_compiler/context/initialize/classes.rs b/crates/erg_compiler/context/initialize/classes.rs
index 7e4617c5f..63a394c3d 100644
--- a/crates/erg_compiler/context/initialize/classes.rs
+++ b/crates/erg_compiler/context/initialize/classes.rs
@@ -569,6 +569,27 @@ impl Context {
             ValueObj::builtin_class(Int),
         );
         int.register_trait(Int, int_floordiv);
+        // needed for implementing `%` operator
+        let mut int_div = Self::builtin_methods(Some(poly(DIV, vec![ty_tp(Int)])), 2);
+        int_div.register_builtin_erg_impl(
+            OP_DIV,
+            fn1_met(Int, Int, Float),
+            Const,
+            Visibility::BUILTIN_PUBLIC,
+        );
+        int_div.register_builtin_const(
+            OUTPUT,
+            Visibility::BUILTIN_PUBLIC,
+            None,
+            ValueObj::builtin_class(Float),
+        );
+        int_div.register_builtin_const(
+            MOD_OUTPUT,
+            Visibility::BUILTIN_PUBLIC,
+            None,
+            ValueObj::builtin_class(Int),
+        );
+        int.register_trait(Int, int_div);
         let mut int_pos = Self::builtin_methods(Some(mono(POS)), 2);
         int_pos.register_builtin_const(
             OUTPUT,
@@ -708,6 +729,27 @@ impl Context {
             ValueObj::builtin_class(Nat),
         );
         nat.register_trait(Nat, nat_floordiv);
+        // needed for implementing `%` operator
+        let mut nat_div = Self::builtin_methods(Some(poly(DIV, vec![ty_tp(Nat)])), 2);
+        nat_div.register_builtin_erg_impl(
+            OP_DIV,
+            fn1_met(Nat, Nat, Float),
+            Const,
+            Visibility::BUILTIN_PUBLIC,
+        );
+        nat_div.register_builtin_const(
+            OUTPUT,
+            Visibility::BUILTIN_PUBLIC,
+            None,
+            ValueObj::builtin_class(Float),
+        );
+        nat_div.register_builtin_const(
+            MOD_OUTPUT,
+            Visibility::BUILTIN_PUBLIC,
+            None,
+            ValueObj::builtin_class(Nat),
+        );
+        nat.register_trait(Nat, nat_div);
         let mut nat_mutizable = Self::builtin_methods(Some(mono(MUTIZABLE)), 2);
         nat_mutizable.register_builtin_const(
             MUTABLE_MUT_TYPE,
diff --git a/crates/erg_compiler/ty/free.rs b/crates/erg_compiler/ty/free.rs
index d440c5ba4..a0f18b6b5 100644
--- a/crates/erg_compiler/ty/free.rs
+++ b/crates/erg_compiler/ty/free.rs
@@ -215,6 +215,7 @@ impl Constraint {
         }
     }
 
+    /// :> Sub, <: Sup
     pub fn get_sub_sup(&self) -> Option<(&Type, &Type)> {
         match self {
             Self::Sandwiched { sub, sup, .. } => Some((sub, sup)),
@@ -1075,6 +1076,7 @@ impl<T: CanbeFree + Send + Clone> Free<T> {
         self.constraint().and_then(|c| c.get_sub().cloned())
     }
 
+    /// :> Sub, <: Super
     pub fn get_subsup(&self) -> Option<(Type, Type)> {
         self.constraint()
             .and_then(|c| c.get_sub_sup().map(|(sub, sup)| (sub.clone(), sup.clone())))
diff --git a/tests/should_ok/operators.er b/tests/should_ok/operators.er
index e941db3a9..db4ec398b 100644
--- a/tests/should_ok/operators.er
+++ b/tests/should_ok/operators.er
@@ -1,3 +1,10 @@
+assert 1 + 1 == 2
+assert 1 - 1 == 0
+assert 1 * 1 == 1
+assert nat(1 / 1) == 1
+assert 1 % 1 == 0
+assert 1 ** 1 == 1
+
 assert 1 in [1, 2]
 assert 1 in (1, 2)
 assert 1 in {1, 2}