diff --git a/.travis.yml b/.travis.yml
index 2c000ad..72127a2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,6 +9,14 @@ matrix:
       dist: trusty
       addons: { apt: { sources: ubuntu-toolchain-r-test, packages: ["xorg-dev", "g++-8"] } }
       env: MATRIX_EVAL="CC=gcc-8 && CXX=g++-8"
+    - os: linux
+      dist: trusty
+      addons: { apt: { sources: ["ubuntu-toolchain-r-test", "llvm-toolchain-trusty-5.0"], packages: ["xorg-dev", "clang-5.0", "g++-7"] } }
+      env: MATRIX_EVAL="CC=clang-5.0 && CXX=clang++-5.0"
+    - os: linux
+      dist: trusty
+      addons: { apt: { sources: ["ubuntu-toolchain-r-test", "llvm-toolchain-trusty-6.0"], packages: ["xorg-dev", "clang-6.0", "g++-7"] } }
+      env: MATRIX_EVAL="CC=clang-6.0 && CXX=clang++-6.0"
     - os: linux
       dist: trusty
       addons: { apt: { sources: ["ubuntu-toolchain-r-test", "llvm-toolchain-trusty-7"], packages: ["xorg-dev", "clang-7", "g++-7"] } }
diff --git a/README.md b/README.md
index 2d6d68e..6dee0d1 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@
 ## Requirements
 
 - [gcc](https://www.gnu.org/software/gcc/) **>= 7**
-- [clang](https://clang.llvm.org/) **>= 7.0**
+- [clang](https://clang.llvm.org/) **>= 5.0**
 - [msvc](https://visualstudio.microsoft.com/) **>= 2017**
 
 ## Installation
@@ -63,38 +63,7 @@ enum debug_level : int {
 };
 
 struct debug_level_traits {
-    using underlying_type = int;
-    static constexpr std::size_t size = 3;
-
-    static constexpr const debug_level values[] = {
-        level_info,
-        level_warning,
-        level_warning
-    };
-
-    static constexpr const std::string_view names[] = {
-        "level_info",
-        "level_warning",
-        "level_warning"
-    };
-
-    static constexpr underlying_type to_underlying(debug_level e) noexcept;
-
-    static constexpr std::optional<std::string_view> to_string(debug_level e) noexcept;
-    static constexpr std::string_view to_string_or_empty(Enum e) noexcept;
-    static std::string_view to_string_or_throw(Enum e);
-
-    static constexpr std::optional<debug_level> from_string(std::string_view name) noexcept;
-    static constexpr debug_level from_string_or_default(std::string_view name, debug_level def) noexcept;
-    static debug_level from_string_or_throw(std::string_view name);
-
-    static constexpr std::optional<std::size_t> to_index(debug_level e) noexcept;
-    static constexpr std::size_t to_index_or_invalid(debug_level e) noexcept;
-    static std::size_t to_index_or_throw(debug_level e);
-
-    static constexpr std::optional<debug_level> from_index(std::size_t index) noexcept;
-    static constexpr debug_level from_index_or_default(std::size_t index, debug_level def) noexcept;
-    static debug_level from_index_or_throw(std::size_t index);
+    /*...*/
 };
 ```
 
@@ -115,40 +84,7 @@ enum class color : unsigned {
 };
 
 struct color_traits {
-    using underlying_type = unsigned;
-    static constexpr std::size_t size = 4;
-
-    static constexpr const color values[] = {
-        color::red,
-        color::green,
-        color::blue,
-        color::white
-    };
-
-    static constexpr const std::string_view names[] = {
-        "red",
-        "green",
-        "blue",
-        "white"
-    };
-
-    static constexpr underlying_type to_underlying(color e) noexcept;
-
-    static constexpr std::optional<std::string_view> to_string(color e) noexcept;
-    static constexpr std::string_view to_string_or_empty(Enum e) noexcept;
-    static std::string_view to_string_or_throw(Enum e);
-
-    static constexpr std::optional<color> from_string(std::string_view name) noexcept;
-    static constexpr color from_string_or_default(std::string_view name, color def) noexcept;
-    static color from_string_or_throw(std::string_view name);
-
-    static constexpr std::optional<std::size_t> to_index(color e) noexcept;
-    static constexpr std::size_t to_index_or_invalid(color e) noexcept;
-    static std::size_t to_index_or_throw(color e);
-
-    static constexpr std::optional<color> from_index(std::size_t index) noexcept;
-    static constexpr color from_index_or_default(std::size_t index, color def) noexcept;
-    static color from_index_or_throw(std::size_t index);
+    /*...*/
 };
 ```
 
@@ -196,6 +132,180 @@ int main() {
 }
 ```
 
+### Generic context
+
+```cpp
+namespace some_namespace
+{
+    ENUM_HPP_CLASS_DECL(color, unsigned,
+        (red = 0xFF0000)
+        (green = 0x00FF00)
+        (blue = 0x0000FF)
+        (white = red | green | blue))
+}
+
+// register traits in global namespace to generic access
+ENUM_HPP_REGISTER_TRAITS(color)
+
+int main() {
+    using color = some_namespace::color;
+
+    // to string
+    static_assert(enum_hpp::to_string(color::red) == "red");
+
+    // from string
+    static_assert(enum_hpp::from_string<color>("red") == color::red);
+
+    return 0;
+}
+```
+
+### Adapting external enums
+
+```cpp
+namespace external_ns
+{
+    enum class external_enum : unsigned short {
+        a = 10,
+        b,
+        c = a + b
+    };
+
+    // should be in the same namespace
+    ENUM_HPP_TRAITS_DECL(external_enum,
+        (a)
+        (b)
+        (c))
+}
+
+ENUM_HPP_REGISTER_TRAITS(external_ns::external_enum)
+
+int main() {
+    using ee = external_ns::external_enum;
+    static_assert(enum_hpp::to_string(ee::a) == "a");
+    static_assert(enum_hpp::from_string<ee>("c") == ee::c);
+    return 0;
+}
+```
+
+## API
+
+### Enum traits
+
+```cpp
+// declare enum
+ENUM_HPP_DECL(
+    /*enum_name*/,
+    /*underlying_type*/,
+    /*fields*/)
+
+// declare enum class
+ENUM_HPP_CLASS_DECL(
+    /*enum_name*/,
+    /*underlying_type*/,
+    /*fields*/)
+
+// declare only traits
+ENUM_HPP_TRAITS_DECL(
+    /*enum_name*/,
+    /*fields*/)
+
+struct /*enum_name*/_traits {
+    using underlying_type = /*underlying_type*/;
+    static constexpr std::size_t size = /*field_count*/;
+
+    static constexpr const std::array</*enum_name*/, /*field_count*/ > values = {
+        /*enum values*/
+    };
+
+    static constexpr const std::array<std::string_view, /*field_count*/> names = {
+        /*enum names*/
+    };
+
+    static constexpr /*underlying_type*/ to_underlying(/*enum_name*/ e) noexcept;
+
+    static constexpr std::optional<std::string_view> to_string(/*enum_name*/ e) noexcept;
+    static constexpr std::string_view to_string_or_empty(/*enum_name*/ e) noexcept;
+    static std::string_view to_string_or_throw(/*enum_name*/ e);
+
+    static constexpr std::optional</*enum_name*/> from_string(std::string_view name) noexcept;
+    static constexpr /*enum_name*/ from_string_or_default(std::string_view name, /*enum_name*/ def) noexcept;
+    static /*enum_name*/ from_string_or_throw(std::string_view name);
+
+    static constexpr std::optional<std::size_t> to_index(/*enum_name*/ e) noexcept;
+    static constexpr std::size_t to_index_or_invalid(/*enum_name*/ e) noexcept;
+    static std::size_t to_index_or_throw(/*enum_name*/ e);
+
+    static constexpr std::optional</*enum_name*/> from_index(std::size_t index) noexcept;
+    static constexpr /*enum_name*/ from_index_or_default(std::size_t index, /*enum_name*/ def) noexcept;
+    static /*enum_name*/ from_index_or_throw(std::size_t index);
+};
+```
+
+### Generic functions
+
+```cpp
+// should be in global namespace
+ENUM_HPP_REGISTER_TRAITS(/*declared_enum_name*/)
+
+namespace enum_hpp
+{
+    template < typename Enum >
+    using traits_t = typename traits<Enum>::type;
+
+    template < typename Enum >
+    using underlying_type = typename traits_t<Enum>::underlying_type;
+
+    template < typename Enum >
+    constexpr std::size_t size() noexcept;
+
+    template < typename Enum >
+    constexpr const std::array<Enum, size<Enum>()>& values() noexcept;
+
+    template < typename Enum >
+    constexpr const std::array<std::string_view, size<Enum>()>& names() noexcept;
+
+    template < typename Enum >
+    constexpr typename traits_t<Enum>::underlying_type to_underlying(Enum e) noexcept;
+
+    template < typename Enum >
+    constexpr std::optional<std::string_view> to_string(Enum e) noexcept;
+
+    template < typename Enum >
+    constexpr std::string_view to_string_or_empty(Enum e) noexcept;
+
+    template < typename Enum >
+    std::string_view to_string_or_throw(Enum e);
+
+    template < typename Enum >
+    constexpr std::optional<Enum> from_string(std::string_view name) noexcept;
+
+    template < typename Enum >
+    constexpr Enum from_string_or_default(std::string_view name, Enum def) noexcept;
+
+    template < typename Enum >
+    Enum from_string_or_throw(std::string_view name);
+
+    template < typename Enum >
+    constexpr std::optional<std::size_t> to_index(Enum e) noexcept;
+
+    template < typename Enum >
+    constexpr std::size_t to_index_or_invalid(Enum e) noexcept;
+
+    template < typename Enum >
+    std::size_t to_index_or_throw(Enum e);
+
+    template < typename Enum >
+    constexpr std::optional<Enum> from_index(std::size_t index) noexcept;
+
+    template < typename Enum >
+    constexpr Enum from_index_or_default(std::size_t index, Enum def) noexcept;
+
+    template < typename Enum >
+    Enum from_index_or_throw(std::size_t index);
+}
+```
+
 ## Alternatives
 
 [Better Enums](https://github.com/aantron/better-enums)
diff --git a/headers/enum.hpp/enum.hpp b/headers/enum.hpp/enum.hpp
index c3318e1..a2d460e 100644
--- a/headers/enum.hpp/enum.hpp
+++ b/headers/enum.hpp/enum.hpp
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <array>
 #include <optional>
 #include <stdexcept>
 #include <string_view>
@@ -23,6 +24,98 @@ namespace enum_hpp
     };
 }
 
+namespace enum_hpp
+{
+    template < typename Enum >
+    struct traits;
+
+    template < typename Enum >
+    using traits_t = typename traits<Enum>::type;
+
+    template < typename Enum >
+    using underlying_type = typename traits_t<Enum>::underlying_type;
+
+    template < typename Enum >
+    constexpr std::size_t size() noexcept {
+        return traits_t<Enum>::size;
+    }
+
+    template < typename Enum >
+    constexpr const std::array<Enum, size<Enum>()>& values() noexcept {
+        return traits_t<Enum>::values;
+    }
+
+    template < typename Enum >
+    constexpr const std::array<std::string_view, size<Enum>()>& names() noexcept {
+        return traits_t<Enum>::names;
+    }
+
+    template < typename Enum >
+    constexpr typename traits_t<Enum>::underlying_type to_underlying(Enum e) noexcept {
+        return traits_t<Enum>::to_underlying(e);
+    }
+
+    template < typename Enum >
+    constexpr std::optional<std::string_view> to_string(Enum e) noexcept {
+        return traits_t<Enum>::to_string(e);
+    }
+
+    template < typename Enum >
+    constexpr std::string_view to_string_or_empty(Enum e) noexcept {
+        return traits_t<Enum>::to_string_or_empty(e);
+    }
+
+    template < typename Enum >
+    std::string_view to_string_or_throw(Enum e) {
+        return traits_t<Enum>::to_string_or_throw(e);
+    }
+
+    template < typename Enum >
+    constexpr std::optional<Enum> from_string(std::string_view name) noexcept {
+        return traits_t<Enum>::from_string(name);
+    }
+
+    template < typename Enum >
+    constexpr Enum from_string_or_default(std::string_view name, Enum def) noexcept {
+        return traits_t<Enum>::from_string_or_default(name, def);
+    }
+
+    template < typename Enum >
+    Enum from_string_or_throw(std::string_view name) {
+        return traits_t<Enum>::from_string_or_throw(name);
+    }
+
+    template < typename Enum >
+    constexpr std::optional<std::size_t> to_index(Enum e) noexcept {
+        return traits_t<Enum>::to_index(e);
+    }
+
+    template < typename Enum >
+    constexpr std::size_t to_index_or_invalid(Enum e) noexcept {
+        return traits_t<Enum>::to_index_or_invalid(e);
+    }
+
+    template < typename Enum >
+    std::size_t to_index_or_throw(Enum e) {
+        return traits_t<Enum>::to_index_or_throw(e);
+    }
+
+    template < typename Enum >
+    constexpr std::optional<Enum> from_index(std::size_t index) noexcept {
+        return traits_t<Enum>::from_index(index);
+    }
+
+    template < typename Enum >
+    constexpr Enum from_index_or_default(std::size_t index, Enum def) noexcept {
+        return traits_t<Enum>::from_index_or_default(index, def);
+    }
+
+    template < typename Enum >
+    Enum from_index_or_throw(std::size_t index) {
+        return traits_t<Enum>::from_index_or_throw(index);
+    }
+}
+
 namespace enum_hpp::detail
 {
     template < typename Enum >
@@ -118,12 +211,20 @@ namespace enum_hpp::detail
 #define ENUM_HPP_TRAITS_DECL(Enum, Fields)\
     struct Enum##_traits {\
     private:\
-        enum enum_names_for_this_score_ { ENUM_HPP_GENERATE_ENUM_FIELDS(Fields) };\
+        enum enum_names_for_this_score_ {\
+            ENUM_HPP_GENERATE_ENUM_FIELDS(Fields)\
+        };\
     public:\
         using underlying_type = std::underlying_type_t<Enum>;\
         static constexpr std::size_t size = ENUM_HPP_PP_SEQ_SIZE(Fields);\
-        static constexpr const Enum values[] = { ENUM_HPP_GENERATE_VALUES(Enum, Fields) };\
-        static constexpr const std::string_view names[] = { ENUM_HPP_GENERATE_NAMES(Fields) };\
+        \
+        static constexpr const std::array<Enum, size> values = {\
+            ENUM_HPP_GENERATE_VALUES(Enum, Fields)\
+        };\
+        \
+        static constexpr const std::array<std::string_view, size> names = {\
+            ENUM_HPP_GENERATE_NAMES(Fields)\
+        };\
     public:\
         static constexpr underlying_type to_underlying(Enum e) noexcept {\
             return static_cast<underlying_type>(e);\
@@ -213,6 +314,16 @@ namespace enum_hpp::detail
         }\
     };
 
+//
+// ENUM_HPP_REGISTER_TRAITS
+//
+
+#define ENUM_HPP_REGISTER_TRAITS(Enum)\
+    template <>\
+    struct enum_hpp::traits<Enum> {\
+        using type = Enum##_traits;\
+    };
+
 // -----------------------------------------------------------------------------
 //
 // ENUM_HPP_PP
diff --git a/untests/enum_examples.cpp b/untests/enum_examples.cpp
index e260e3f..e49598d 100644
--- a/untests/enum_examples.cpp
+++ b/untests/enum_examples.cpp
@@ -21,6 +21,8 @@ namespace
         (white = red | green | blue))
 }
 
+ENUM_HPP_REGISTER_TRAITS(color)
+
 TEST_CASE("examples") {
     SECTION("traits_using") {
         // size
@@ -50,4 +52,12 @@ TEST_CASE("examples") {
             std::cout << n << ",";
         } // stdout: red,green,blue,
     }
+
+    SECTION("generic_context") {
+        // to string
+        static_assert(enum_hpp::to_string(color::red) == "red");
+
+        // from string
+        static_assert(enum_hpp::from_string<color>("red") == color::red);
+    }
 }
diff --git a/untests/enum_tests.cpp b/untests/enum_tests.cpp
index d3756bf..bd67a75 100644
--- a/untests/enum_tests.cpp
+++ b/untests/enum_tests.cpp
@@ -53,8 +53,26 @@ namespace some_namespace
         (_181)(_182)(_183)(_184)(_185)(_186)(_187)(_188)(_189)(_190)(_191)(_192)(_193)(_194)(_195)(_196)(_197)(_198)(_199)(_200)
         (_201)(_202)(_203)(_204)(_205)(_206)(_207)(_208)(_209)(_210)(_211)(_212)(_213)(_214)(_215)(_216)(_217)(_218)(_219)(_220)
         (_221)(_222)(_223)(_224)(_225)(_226)(_227)(_228)(_229)(_230)(_231)(_232)(_233)(_234)(_235)(_236)(_237)(_238)(_239)(_240))
+
+    namespace exns
+    {
+        enum class external_enum : unsigned short {
+            a = 10,
+            b,
+            c = a + b
+        };
+
+        ENUM_HPP_TRAITS_DECL(external_enum,
+            (a)
+            (b)
+            (c))
+    }
 }
 
+ENUM_HPP_REGISTER_TRAITS(some_namespace::color)
+ENUM_HPP_REGISTER_TRAITS(some_namespace::numbers)
+ENUM_HPP_REGISTER_TRAITS(some_namespace::exns::external_enum)
+
 TEST_CASE("enum") {
     namespace sn = some_namespace;
 
@@ -64,6 +82,14 @@ TEST_CASE("enum") {
                 std::underlying_type_t<sn::color>,
                 unsigned>);
 
+            STATIC_REQUIRE(std::is_same_v<
+                sn::color_traits::underlying_type,
+                enum_hpp::underlying_type<sn::color>>);
+
+            STATIC_REQUIRE(std::is_same_v<
+                sn::color_traits,
+                enum_hpp::traits_t<sn::color>>);
+
             REQUIRE(enum_to_underlying(sn::color::red) == 2u);
             REQUIRE(enum_to_underlying(sn::color::green) == 3u);
             REQUIRE(enum_to_underlying(sn::color::blue) == 6u);
@@ -83,6 +109,14 @@ TEST_CASE("enum") {
                 std::underlying_type_t<sn::numbers>,
                 int>);
 
+            STATIC_REQUIRE(std::is_same_v<
+                sn::numbers_traits::underlying_type,
+                enum_hpp::underlying_type<sn::numbers>>);
+
+            STATIC_REQUIRE(std::is_same_v<
+                sn::numbers_traits,
+                enum_hpp::traits_t<sn::numbers>>);
+
             REQUIRE(enum_to_underlying(sn::_0) == 0);
             REQUIRE(enum_to_underlying(sn::_100) == 100);
             REQUIRE(enum_to_underlying(sn::_240) == 240);
@@ -91,19 +125,29 @@ TEST_CASE("enum") {
 
     SECTION("size") {
         {
-            REQUIRE(sn::color_traits::size == 3u);
-            REQUIRE(sn::color_traits::size == std::size(sn::color_traits::names));
-            REQUIRE(sn::color_traits::size == std::size(sn::color_traits::values));
+            STATIC_REQUIRE(sn::color_traits::size == 3u);
+            STATIC_REQUIRE(sn::color_traits::size == std::size(sn::color_traits::names));
+            STATIC_REQUIRE(sn::color_traits::size == std::size(sn::color_traits::values));
+
+            STATIC_REQUIRE(enum_hpp::size<sn::color>() == 3u);
+            STATIC_REQUIRE(enum_hpp::traits_t<sn::color>::size == 3u);
+            STATIC_REQUIRE(std::size(enum_hpp::names<sn::color>()) == 3u);
+            STATIC_REQUIRE(std::size(enum_hpp::values<sn::color>()) == 3u);
         }
         {
-            REQUIRE(sn::render::mask_traits::size == 4u);
-            REQUIRE(sn::render::mask_traits::size == std::size(sn::render::mask_traits::names));
-            REQUIRE(sn::render::mask_traits::size == std::size(sn::render::mask_traits::values));
+            STATIC_REQUIRE(sn::render::mask_traits::size == 4u);
+            STATIC_REQUIRE(sn::render::mask_traits::size == std::size(sn::render::mask_traits::names));
+            STATIC_REQUIRE(sn::render::mask_traits::size == std::size(sn::render::mask_traits::values));
         }
         {
-            REQUIRE(sn::numbers_traits::size == 241u);
-            REQUIRE(sn::numbers_traits::size == std::size(sn::numbers_traits::names));
-            REQUIRE(sn::numbers_traits::size == std::size(sn::numbers_traits::values));
+            STATIC_REQUIRE(sn::numbers_traits::size == 241u);
+            STATIC_REQUIRE(sn::numbers_traits::size == std::size(sn::numbers_traits::names));
+            STATIC_REQUIRE(sn::numbers_traits::size == std::size(sn::numbers_traits::values));
+
+            STATIC_REQUIRE(enum_hpp::size<sn::numbers>() == 241u);
+            STATIC_REQUIRE(enum_hpp::traits_t<sn::numbers>::size == 241u);
+            STATIC_REQUIRE(std::size(enum_hpp::names<sn::numbers>()) == 241u);
+            STATIC_REQUIRE(std::size(enum_hpp::values<sn::numbers>()) == 241u);
         }
     }
 
@@ -113,6 +157,11 @@ TEST_CASE("enum") {
             STATIC_REQUIRE(sn::color_traits::to_underlying(sn::color::green) == enum_to_underlying(sn::color::green));
             STATIC_REQUIRE(sn::color_traits::to_underlying(sn::color::blue) == enum_to_underlying(sn::color::blue));
             STATIC_REQUIRE(sn::color_traits::to_underlying(sn::color(42)) == 42);
+
+            STATIC_REQUIRE(enum_hpp::to_underlying(sn::color::red) == enum_to_underlying(sn::color::red));
+            STATIC_REQUIRE(enum_hpp::to_underlying(sn::color::green) == enum_to_underlying(sn::color::green));
+            STATIC_REQUIRE(enum_hpp::to_underlying(sn::color::blue) == enum_to_underlying(sn::color::blue));
+            STATIC_REQUIRE(enum_hpp::to_underlying(sn::color(42)) == 42);
         }
         {
             STATIC_REQUIRE(sn::render::mask_traits::to_underlying(sn::render::mask::none) == enum_to_underlying(sn::render::mask::none));
@@ -125,6 +174,11 @@ TEST_CASE("enum") {
             STATIC_REQUIRE(sn::numbers_traits::to_underlying(sn::_180) == enum_to_underlying(sn::_180));
             STATIC_REQUIRE(sn::numbers_traits::to_underlying(sn::_240) == enum_to_underlying(sn::_240));
             STATIC_REQUIRE(sn::numbers_traits::to_underlying(sn::numbers(100500)) == 100500);
+
+            STATIC_REQUIRE(enum_hpp::to_underlying(sn::_0) == enum_to_underlying(sn::_0));
+            STATIC_REQUIRE(enum_hpp::to_underlying(sn::_180) == enum_to_underlying(sn::_180));
+            STATIC_REQUIRE(enum_hpp::to_underlying(sn::_240) == enum_to_underlying(sn::_240));
+            STATIC_REQUIRE(enum_hpp::to_underlying(sn::numbers(100500)) == 100500);
         }
     }
 
@@ -145,6 +199,11 @@ TEST_CASE("enum") {
             STATIC_REQUIRE_FALSE(sn::color_traits::to_string(sn::color(42)));
             STATIC_REQUIRE(sn::color_traits::to_string_or_empty(sn::color(42)) == "");
             REQUIRE_THROWS_AS(sn::color_traits::to_string_or_throw(sn::color(42)), enum_hpp::exception);
+
+            STATIC_REQUIRE(enum_hpp::to_string(sn::color::green) == "green");
+            STATIC_REQUIRE(enum_hpp::to_string_or_empty(sn::color::green) == "green");
+            REQUIRE(enum_hpp::to_string_or_throw(sn::color::green) == "green");
+            REQUIRE_THROWS_AS(enum_hpp::to_string_or_throw(sn::color(42)), enum_hpp::exception);
         }
         {
             STATIC_REQUIRE(sn::render::mask_traits::to_string(sn::render::mask::none) == "none");
@@ -178,6 +237,11 @@ TEST_CASE("enum") {
             STATIC_REQUIRE_FALSE(sn::numbers_traits::to_string(sn::numbers(100500)));
             STATIC_REQUIRE(sn::numbers_traits::to_string_or_empty(sn::numbers(100500)) == "");
             REQUIRE_THROWS_AS(sn::numbers_traits::to_string_or_throw(sn::numbers(100500)), enum_hpp::exception);
+
+            STATIC_REQUIRE(enum_hpp::to_string(sn::_180) == "_180");
+            STATIC_REQUIRE(enum_hpp::to_string_or_empty(sn::_180) == "_180");
+            REQUIRE(enum_hpp::to_string_or_throw(sn::_180) == "_180");
+            REQUIRE_THROWS_AS(enum_hpp::to_string_or_throw(sn::numbers(100500)), enum_hpp::exception);
         }
     }
 
@@ -198,6 +262,11 @@ TEST_CASE("enum") {
             STATIC_REQUIRE_FALSE(sn::color_traits::from_string("42"));
             STATIC_REQUIRE(sn::color_traits::from_string_or_default("42", sn::color::red) == sn::color::red);
             REQUIRE_THROWS_AS(sn::color_traits::from_string_or_throw("42"), enum_hpp::exception);
+
+            STATIC_REQUIRE(enum_hpp::from_string<sn::color>("green") == sn::color::green);
+            STATIC_REQUIRE(enum_hpp::from_string_or_default("green", sn::color::red) == sn::color::green);
+            REQUIRE(enum_hpp::from_string_or_throw<sn::color>("green") == sn::color::green);
+            REQUIRE_THROWS_AS(enum_hpp::from_string_or_throw<sn::color>("42"), enum_hpp::exception);
         }
         {
             STATIC_REQUIRE(sn::render::mask_traits::from_string("none") == sn::render::mask::none);
@@ -210,6 +279,10 @@ TEST_CASE("enum") {
             STATIC_REQUIRE(sn::numbers_traits::from_string("_10") == sn::_10);
             STATIC_REQUIRE(sn::numbers_traits::from_string("_240") == sn::_240);
             STATIC_REQUIRE_FALSE(sn::numbers_traits::from_string("error"));
+
+            STATIC_REQUIRE(enum_hpp::from_string<sn::numbers>("_10") == sn::_10);
+            STATIC_REQUIRE(enum_hpp::from_string<sn::numbers>("_240") == sn::_240);
+            STATIC_REQUIRE_FALSE(enum_hpp::from_string<sn::numbers>("error"));
         }
     }
 
@@ -230,6 +303,11 @@ TEST_CASE("enum") {
             STATIC_REQUIRE_FALSE(sn::color_traits::to_index(sn::color(42)));
             STATIC_REQUIRE(sn::color_traits::to_index_or_invalid(sn::color(42)) == enum_hpp::invalid_index);
             REQUIRE_THROWS_AS(sn::color_traits::to_index_or_throw(sn::color(42)), enum_hpp::exception);
+
+            STATIC_REQUIRE(enum_hpp::to_index(sn::color::green) == 1u);
+            STATIC_REQUIRE(enum_hpp::to_index_or_invalid(sn::color::green) == 1u);
+            REQUIRE(enum_hpp::to_index_or_throw(sn::color::green) == 1u);
+            REQUIRE_THROWS_AS(enum_hpp::to_index_or_throw(sn::color(42)), enum_hpp::exception);
         }
         {
             STATIC_REQUIRE(sn::render::mask_traits::to_index(sn::render::mask::none) == 0u);
@@ -263,6 +341,11 @@ TEST_CASE("enum") {
             STATIC_REQUIRE_FALSE(sn::numbers_traits::to_index(sn::numbers(100500)));
             STATIC_REQUIRE(sn::numbers_traits::to_index_or_invalid(sn::numbers(100500)) == enum_hpp::invalid_index);
             REQUIRE_THROWS_AS(sn::numbers_traits::to_index_or_throw(sn::numbers(100500)), enum_hpp::exception);
+
+            STATIC_REQUIRE(enum_hpp::to_index(sn::_180) == 180u);
+            STATIC_REQUIRE(enum_hpp::to_index_or_invalid(sn::_180) == 180u);
+            REQUIRE(enum_hpp::to_index_or_throw(sn::_180) == 180u);
+            REQUIRE_THROWS_AS(enum_hpp::to_index_or_throw(sn::numbers(100500)), enum_hpp::exception);
         }
     }
 
@@ -283,6 +366,11 @@ TEST_CASE("enum") {
             STATIC_REQUIRE_FALSE(sn::color_traits::from_index(42));
             STATIC_REQUIRE(sn::color_traits::from_index_or_default(42, sn::color::red) == sn::color::red);
             REQUIRE_THROWS_AS(sn::color_traits::from_index_or_throw(42), enum_hpp::exception);
+
+            STATIC_REQUIRE(enum_hpp::from_index<sn::color>(1) == sn::color::green);
+            STATIC_REQUIRE(enum_hpp::from_index_or_default(1, sn::color::red) == sn::color::green);
+            REQUIRE(enum_hpp::from_index_or_throw<sn::color>(1) == sn::color::green);
+            REQUIRE_THROWS_AS(enum_hpp::from_index_or_throw<sn::color>(42), enum_hpp::exception);
         }
         {
             STATIC_REQUIRE(sn::render::mask_traits::from_index(0) == sn::render::mask::none);
@@ -295,6 +383,25 @@ TEST_CASE("enum") {
             STATIC_REQUIRE(sn::numbers_traits::from_index(10) == sn::_10);
             STATIC_REQUIRE(sn::numbers_traits::from_index(240) == sn::_240);
             STATIC_REQUIRE_FALSE(sn::numbers_traits::from_index(100500));
+
+            STATIC_REQUIRE(enum_hpp::from_index<sn::numbers>(10) == sn::_10);
+            STATIC_REQUIRE(enum_hpp::from_index<sn::numbers>(240) == sn::_240);
+            STATIC_REQUIRE_FALSE(enum_hpp::from_index<sn::numbers>(100500));
         }
     }
 }
+
+TEST_CASE("external_enum") {
+    using ee = some_namespace::exns::external_enum;
+    STATIC_REQUIRE(std::is_same_v<enum_hpp::underlying_type<ee>, unsigned short>);
+    STATIC_REQUIRE(enum_hpp::size<ee>() == 3);
+
+    STATIC_REQUIRE(enum_hpp::names<ee>()[0] == "a");
+    STATIC_REQUIRE(enum_hpp::names<ee>()[2] == "c");
+
+    STATIC_REQUIRE(enum_hpp::values<ee>()[0] == ee::a);
+    STATIC_REQUIRE(enum_hpp::values<ee>()[2] == ee::c);
+
+    STATIC_REQUIRE(enum_hpp::to_string(ee::c) == "c");
+    STATIC_REQUIRE(enum_hpp::from_string<ee>("b") == ee::b);
+}