diff --git a/include/bit_op.h b/include/bit_op.h
deleted file mode 100644
index 6f70f09..0000000
--- a/include/bit_op.h
+++ /dev/null
@@ -1 +0,0 @@
-#pragma once
diff --git a/include/operator.h b/include/operator.h
new file mode 100644
index 0000000..3014e80
--- /dev/null
+++ b/include/operator.h
@@ -0,0 +1,75 @@
+#pragma once
+#include "bit.h"
+
+namespace dark {
+
+using dark::concepts::bit_type;
+using dark::concepts::int_type;
+using dark::concepts::bit_match;
+
+template <typename _Tp>
+constexpr auto cast(const _Tp& value) {
+    return static_cast <max_size_t> (value);
+}
+
+template <typename _Tp, typename _Up>
+consteval auto get_common_length() -> std::size_t {
+    static_assert(bit_match <_Tp, _Up>);
+    if constexpr (bit_type <_Tp>) {
+        return _Tp::_Bit_Len;
+    } else {
+        static_assert(bit_type <_Up>, "Invalid common length");
+        return _Up::_Bit_Len;
+    }
+}
+
+template <typename _Tp, typename _Up>
+requires bit_match <_Tp, _Up>
+constexpr auto operator + (const _Tp &lhs, const _Up &rhs) {
+    constexpr auto _Len = get_common_length <_Tp, _Up>();
+    return Bit <_Len> (cast(lhs) + cast(rhs));
+}
+
+template <typename _Tp, typename _Up>
+requires bit_match <_Tp, _Up>
+constexpr auto operator - (const _Tp &lhs, const _Up &rhs) {
+    constexpr auto _Len = get_common_length <_Tp, _Up>();
+    return Bit <_Len> (cast(lhs) + cast(rhs));
+}
+
+template <typename _Tp, typename _Up>
+requires bit_match <_Tp, _Up>
+constexpr auto operator * (const _Tp &lhs, const _Up &rhs) {
+    constexpr auto _Len = get_common_length <_Tp, _Up>();
+    return Bit <_Len> (cast(lhs) + cast(rhs));
+}
+
+template <typename _Tp, typename _Up>
+requires bit_match <_Tp, _Up>
+constexpr auto operator / (const _Tp &lhs, const _Up &rhs) {
+    constexpr auto _Len = get_common_length <_Tp, _Up>();
+    return Bit <_Len> (cast(lhs) + cast(rhs));
+}
+
+template <typename _Tp, typename _Up>
+requires bit_match <_Tp, _Up>
+constexpr auto operator & (const _Tp &lhs, const _Up &rhs) {
+    constexpr auto _Len = get_common_length <_Tp, _Up>();
+    return Bit <_Len> (cast(lhs) + cast(rhs));
+}
+
+template <typename _Tp, typename _Up>
+requires bit_match <_Tp, _Up>
+constexpr auto operator | (const _Tp &lhs, const _Up &rhs) {
+    constexpr auto _Len = get_common_length <_Tp, _Up>();
+    return Bit <_Len> (cast(lhs) + cast(rhs));
+}
+
+template <typename _Tp, typename _Up>
+requires bit_match <_Tp, _Up>
+constexpr auto operator ^ (const _Tp &lhs, const _Up &rhs) {
+    constexpr auto _Len = get_common_length <_Tp, _Up>();
+    return Bit <_Len> (cast(lhs) + cast(rhs));
+}
+
+} // namespace dark