diff --git a/ctl/integral_constant.h b/ctl/integral_constant.h
index df5a0a688..047b27354 100644
--- a/ctl/integral_constant.h
+++ b/ctl/integral_constant.h
@@ -11,10 +11,12 @@ struct integral_constant
     static constexpr T value = v;
     typedef T value_type;
     typedef integral_constant type;
+
     constexpr operator value_type() const noexcept
     {
         return value;
     }
+
     constexpr value_type operator()() const noexcept
     {
         return value;
diff --git a/ctl/is_abstract.h b/ctl/is_abstract.h
new file mode 100644
index 000000000..ccd26c123
--- /dev/null
+++ b/ctl/is_abstract.h
@@ -0,0 +1,18 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_ABSTRACT_H_
+#define CTL_IS_ABSTRACT_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<typename T>
+struct is_abstract : public integral_constant<bool, __is_abstract(T)>
+{};
+
+template<typename T>
+inline constexpr bool is_abstract_v = __is_abstract(T);
+
+} // namespace ctl
+
+#endif // CTL_IS_ABSTRACT_H_
diff --git a/ctl/is_base_of.h b/ctl/is_base_of.h
new file mode 100644
index 000000000..a37456f26
--- /dev/null
+++ b/ctl/is_base_of.h
@@ -0,0 +1,18 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_BASE_OF_H_
+#define CTL_IS_BASE_OF_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<typename Base, typename Derived>
+struct is_base_of : public integral_constant<bool, __is_base_of(Base, Derived)>
+{};
+
+template<typename Base, typename Derived>
+inline constexpr bool is_base_of_v = __is_base_of(Base, Derived);
+
+} // namespace ctl
+
+#endif // CTL_IS_BASE_OF_H_
diff --git a/ctl/is_class.h b/ctl/is_class.h
new file mode 100644
index 000000000..3c958bd17
--- /dev/null
+++ b/ctl/is_class.h
@@ -0,0 +1,18 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_CLASS_H_
+#define CTL_IS_CLASS_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<typename T>
+struct is_class : public integral_constant<bool, __is_class(T)>
+{};
+
+template<typename T>
+inline constexpr bool is_class_v = __is_class(T);
+
+} // namespace ctl
+
+#endif // CTL_IS_CLASS_H_
diff --git a/ctl/is_constructible.h b/ctl/is_constructible.h
new file mode 100644
index 000000000..4d202bdc5
--- /dev/null
+++ b/ctl/is_constructible.h
@@ -0,0 +1,19 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_CONSTRUCTIBLE_H_
+#define CTL_IS_CONSTRUCTIBLE_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<class _Tp, class... _Args>
+struct is_constructible
+  : public integral_constant<bool, __is_constructible(_Tp, _Args...)>
+{};
+
+template<class _Tp, class... _Args>
+inline constexpr bool is_constructible_v = __is_constructible(_Tp, _Args...);
+
+} // namespace ctl
+
+#endif // CTL_IS_CONSTRUCTIBLE_H_
diff --git a/ctl/is_empty.h b/ctl/is_empty.h
new file mode 100644
index 000000000..a1cf31675
--- /dev/null
+++ b/ctl/is_empty.h
@@ -0,0 +1,18 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_EMPTY_H_
+#define CTL_IS_EMPTY_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<typename T>
+struct is_empty : public integral_constant<bool, __is_empty(T)>
+{};
+
+template<typename T>
+inline constexpr bool is_empty_v = __is_empty(T);
+
+} // namespace ctl
+
+#endif // CTL_IS_EMPTY_H_
diff --git a/ctl/is_enum.h b/ctl/is_enum.h
new file mode 100644
index 000000000..7d2cd5b78
--- /dev/null
+++ b/ctl/is_enum.h
@@ -0,0 +1,18 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_ENUM_H_
+#define CTL_IS_ENUM_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<typename T>
+struct is_enum : public integral_constant<bool, __is_enum(T)>
+{};
+
+template<typename T>
+inline constexpr bool is_enum_v = __is_enum(T);
+
+} // namespace ctl
+
+#endif // CTL_IS_ENUM_H_
diff --git a/ctl/is_polymorphic.h b/ctl/is_polymorphic.h
new file mode 100644
index 000000000..152b7af0b
--- /dev/null
+++ b/ctl/is_polymorphic.h
@@ -0,0 +1,18 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_POLYMORPHIC_H_
+#define CTL_IS_POLYMORPHIC_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<typename T>
+struct is_polymorphic : public integral_constant<bool, __is_polymorphic(T)>
+{};
+
+template<typename T>
+inline constexpr bool is_polymorphic_v = __is_polymorphic(T);
+
+} // namespace ctl
+
+#endif // CTL_IS_POLYMORPHIC_H_
diff --git a/ctl/is_standard_layout.h b/ctl/is_standard_layout.h
new file mode 100644
index 000000000..59ae380c8
--- /dev/null
+++ b/ctl/is_standard_layout.h
@@ -0,0 +1,19 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_STANDARD_LAYOUT_H_
+#define CTL_IS_STANDARD_LAYOUT_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<typename T>
+struct is_standard_layout
+  : public integral_constant<bool, __is_standard_layout(T)>
+{};
+
+template<typename T>
+inline constexpr bool is_standard_layout_v = __is_standard_layout(T);
+
+} // namespace ctl
+
+#endif // CTL_IS_STANDARD_LAYOUT_H_
diff --git a/ctl/is_trivial.h b/ctl/is_trivial.h
new file mode 100644
index 000000000..c69c18f08
--- /dev/null
+++ b/ctl/is_trivial.h
@@ -0,0 +1,18 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_TRIVIAL_H_
+#define CTL_IS_TRIVIAL_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<typename T>
+struct is_trivial : public integral_constant<bool, __is_trivial(T)>
+{};
+
+template<typename T>
+inline constexpr bool is_trivial_v = __is_trivial(T);
+
+} // namespace ctl
+
+#endif // CTL_IS_TRIVIAL_H_
diff --git a/ctl/is_union.h b/ctl/is_union.h
new file mode 100644
index 000000000..773c52e3b
--- /dev/null
+++ b/ctl/is_union.h
@@ -0,0 +1,18 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_UNION_H_
+#define CTL_IS_UNION_H_
+#include "integral_constant.h"
+
+namespace ctl {
+
+template<typename T>
+struct is_union : public integral_constant<bool, __is_union(T)>
+{};
+
+template<typename T>
+inline constexpr bool is_union_v = __is_union(T);
+
+} // namespace ctl
+
+#endif // CTL_IS_UNION_H_
diff --git a/test/ctl/is_base_of_test.cc b/test/ctl/is_base_of_test.cc
new file mode 100644
index 000000000..8e64a75af
--- /dev/null
+++ b/test/ctl/is_base_of_test.cc
@@ -0,0 +1,102 @@
+// -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+//
+// Copyright 2024 Justine Alexandra Roberts Tunney
+//
+// Permission to use, copy, modify, and/or distribute this software for
+// any purpose with or without fee is hereby granted, provided that the
+// above copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+// WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
+// AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+// DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+// PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+// TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+#include "ctl/is_base_of.h"
+
+// #include <type_traits>
+// #define ctl std
+
+// Test classes
+class A
+{};
+class B : public A
+{};
+class C : public B
+{};
+class D
+{};
+
+struct Empty
+{};
+
+template<typename T>
+class TemplateClass
+{};
+
+class VirtualBase
+{};
+class VirtualDerived : virtual public VirtualBase
+{};
+
+int
+main()
+{
+    // Test basic inheritance
+    if (!ctl::is_base_of_v<A, B>)
+        return 1;
+    if (!ctl::is_base_of_v<A, C>)
+        return 2;
+    if (ctl::is_base_of_v<B, A>)
+        return 3;
+    if (ctl::is_base_of_v<C, A>)
+        return 4;
+    if (ctl::is_base_of_v<A, D>)
+        return 5;
+
+    // Test with same type
+    if (!ctl::is_base_of_v<A, A>)
+        return 6;
+    if (!ctl::is_base_of_v<B, B>)
+        return 7;
+
+    // Test with void
+    if (ctl::is_base_of_v<void, void>)
+        return 8;
+    if (ctl::is_base_of_v<A, void>)
+        return 9;
+    if (ctl::is_base_of_v<void, A>)
+        return 10;
+
+    // Test with fundamental types
+    if (ctl::is_base_of_v<int, int>)
+        return 11;
+    if (ctl::is_base_of_v<int, double>)
+        return 12;
+    if (ctl::is_base_of_v<double, int>)
+        return 13;
+
+    // Test with empty class
+    if (ctl::is_base_of_v<Empty, A>)
+        return 14;
+    if (ctl::is_base_of_v<A, Empty>)
+        return 15;
+
+    // Test with template class
+    if (ctl::is_base_of_v<TemplateClass<int>, A>)
+        return 16;
+    if (ctl::is_base_of_v<A, TemplateClass<int>>)
+        return 17;
+
+    // Test with virtual inheritance
+    if (!ctl::is_base_of_v<VirtualBase, VirtualDerived>)
+        return 18;
+    if (ctl::is_base_of_v<VirtualDerived, VirtualBase>)
+        return 19;
+
+    return 0; // All tests passed
+}