diff --git a/headers/kari.hpp/kari.hpp b/headers/kari.hpp/kari.hpp
index 2d9047a..55805da 100644
--- a/headers/kari.hpp/kari.hpp
+++ b/headers/kari.hpp/kari.hpp
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <functional>
 #include <tuple>
 #include <type_traits>
 #include <utility>
@@ -109,3 +110,196 @@ namespace kari_hpp
         return curry(std::forward<F>(f))(std::forward<A>(a), std::forward<As>(as)...);
     }
 }
+
+namespace kari_hpp::ext
+{
+    //
+    // fid
+    //
+
+    struct fid_t {
+        template < typename A >
+        constexpr auto operator()(A&& a) const {
+            return std::forward<A>(a);
+        }
+    };
+    inline constexpr auto fid = curry(fid_t{});
+
+    //
+    // fconst
+    //
+
+    struct fconst_t {
+        template < typename A, typename B >
+        constexpr auto operator()(A&& a, [[maybe_unused]] B&& b) const {
+            return std::forward<A>(a);
+        }
+    };
+    inline constexpr auto fconst = curry(fconst_t{});
+
+    //
+    // fflip
+    //
+
+    struct fflip_t {
+        template < typename F, typename A, typename B >
+        constexpr auto operator()(F&& f, A&& a, B&& b) const {
+            return curry(std::forward<F>(f), std::forward<B>(b), std::forward<A>(a));
+        }
+    };
+    inline constexpr auto fflip = curry(fflip_t{});
+
+    //
+    // fpipe
+    //
+
+    struct fpipe_t {
+        template < typename G, typename F, typename A >
+        constexpr auto operator()(G&& g, F&& f, A&& a) const {
+            return curry(
+                std::forward<F>(f),
+                curry(std::forward<G>(g), std::forward<A>(a)));
+        }
+    };
+    inline constexpr auto fpipe = curry(fpipe_t{});
+
+    //
+    // fcompose
+    //
+
+    struct fcompose_t {
+        template < typename G, typename F, typename A >
+        constexpr auto operator()(G&& g, F&& f, A&& a) const {
+            return curry(
+                std::forward<G>(g),
+                curry(std::forward<F>(f), std::forward<A>(a)));
+        }
+    };
+    inline constexpr auto fcompose = curry(fcompose_t{});
+
+    //
+    // fpipe operators
+    //
+
+    template < typename G, typename F
+             , std::enable_if_t<std::disjunction_v<
+                is_curried<std::decay_t<G>>,
+                is_curried<std::decay_t<F>>>, int> = 0 >
+    constexpr auto operator|(G&& g, F&& f) {
+        constexpr bool gc = is_curried_v<std::decay_t<G>>;
+        constexpr bool fc = is_curried_v<std::decay_t<F>>;
+
+        if constexpr ( gc && fc ) {
+            return fpipe(std::forward<G>(g), std::forward<F>(f));
+        }
+
+        if constexpr ( gc && !fc) {
+            return std::forward<G>(g)(std::forward<F>(f));
+        }
+
+        if constexpr ( !gc && fc) {
+            return std::forward<F>(f)(std::forward<G>(g));
+        }
+
+        static_assert(gc || fc, "F or G or both arguments should be curried");
+    }
+
+    //
+    // fcompose operators
+    //
+
+    template < typename G, typename F
+             , std::enable_if_t<std::disjunction_v<
+                is_curried<std::decay_t<G>>,
+                is_curried<std::decay_t<F>>>, int> = 0 >
+    constexpr auto operator*(G&& g, F&& f) {
+        constexpr bool gc = is_curried_v<std::decay_t<G>>;
+        constexpr bool fc = is_curried_v<std::decay_t<F>>;
+
+        if constexpr ( gc && fc ) {
+            return fcompose(std::forward<G>(g), std::forward<F>(f));
+        }
+
+        if constexpr ( gc && !fc) {
+            return std::forward<G>(g)(std::forward<F>(f));
+        }
+
+        if constexpr ( !gc && fc) {
+            return std::forward<F>(f)(std::forward<G>(g));
+        }
+
+        static_assert(gc || fc, "F or G or both arguments should be curried");
+    }
+}
+
+namespace kari_hpp::ext::underscore
+{
+    struct us_t {};
+    inline constexpr us_t _{};
+
+    //
+    // is_underscore, is_underscore_v
+    //
+
+    template < typename T >
+    struct is_underscore
+    : std::bool_constant<std::is_same_v<us_t, std::remove_cv_t<T>>> {};
+
+    template < typename T >
+    inline constexpr bool is_underscore_v = is_underscore<T>::value;
+
+    //
+    // unary operators
+    //
+
+    #define KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP(op, func)\
+        constexpr auto operator op (us_t) {\
+            return curry(func);\
+        }
+
+        KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP(-, std::negate<>())
+        KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP(~, std::bit_not<>())
+        KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP(!, std::logical_not<>())
+    #undef KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP
+
+    //
+    // binary operators
+    //
+
+    #define KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(op, func)\
+        constexpr auto operator op (us_t, us_t) {\
+            return curry(func);\
+        }\
+        \
+        template < typename A, std::enable_if_t<!is_underscore_v<std::decay_t<A>>, int> = 0 >\
+        constexpr auto operator op (A&& a, us_t) {\
+            return curry(func, std::forward<A>(a));\
+        }\
+        \
+        template < typename B, std::enable_if_t<!is_underscore_v<std::decay_t<B>>, int> = 0 >\
+        constexpr auto operator op (us_t, B&& b) {\
+            return fflip(func, std::forward<B>(b));\
+        }
+
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(+ , std::plus<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(- , std::minus<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(* , std::multiplies<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(/ , std::divides<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(% , std::modulus<>())
+
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(< , std::less<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(> , std::greater<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(<=, std::less_equal<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(>=, std::greater_equal<>())
+
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(==, std::equal_to<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(!=, std::not_equal_to<>())
+
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(| , std::bit_or<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(& , std::bit_and<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(^ , std::bit_xor<>())
+
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(||, std::logical_or<>())
+        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(&&, std::logical_and<>())
+    #undef KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP
+}
diff --git a/headers/kari.hpp/kari_ext.hpp b/headers/kari.hpp/kari_ext.hpp
deleted file mode 100644
index 8415a3e..0000000
--- a/headers/kari.hpp/kari_ext.hpp
+++ /dev/null
@@ -1,206 +0,0 @@
-/*******************************************************************************
- * This file is part of the "https://github.com/BlackMATov/kari.hpp"
- * For conditions of distribution and use, see copyright notice in LICENSE.md
- * Copyright (C) 2017-2020, by Matvey Cherevko (blackmatov@gmail.com)
- ******************************************************************************/
-
-#pragma once
-
-#include "kari.hpp"
-
-#include <functional>
-#include <type_traits>
-#include <utility>
-
-namespace kari_hpp
-{
-    //
-    // fid
-    //
-
-    struct fid_t {
-        template < typename A >
-        constexpr auto operator()(A&& a) const {
-            return std::forward<A>(a);
-        }
-    };
-    inline constexpr auto fid = curry(fid_t{});
-
-    //
-    // fconst
-    //
-
-    struct fconst_t {
-        template < typename A, typename B >
-        constexpr auto operator()(A&& a, [[maybe_unused]] B&& b) const {
-            return std::forward<A>(a);
-        }
-    };
-    inline constexpr auto fconst = curry(fconst_t{});
-
-    //
-    // fflip
-    //
-
-    struct fflip_t {
-        template < typename F, typename A, typename B >
-        constexpr auto operator()(F&& f, A&& a, B&& b) const {
-            return curry(std::forward<F>(f), std::forward<B>(b), std::forward<A>(a));
-        }
-    };
-    inline constexpr auto fflip = curry(fflip_t{});
-
-    //
-    // fpipe
-    //
-
-    struct fpipe_t {
-        template < typename G, typename F, typename A >
-        constexpr auto operator()(G&& g, F&& f, A&& a) const {
-            return curry(
-                std::forward<F>(f),
-                curry(std::forward<G>(g), std::forward<A>(a)));
-        }
-    };
-    inline constexpr auto fpipe = curry(fpipe_t{});
-
-    //
-    // fcompose
-    //
-
-    struct fcompose_t {
-        template < typename G, typename F, typename A >
-        constexpr auto operator()(G&& g, F&& f, A&& a) const {
-            return curry(
-                std::forward<G>(g),
-                curry(std::forward<F>(f), std::forward<A>(a)));
-        }
-    };
-    inline constexpr auto fcompose = curry(fcompose_t{});
-
-    //
-    // fpipe operators
-    //
-
-    template < typename G, typename F
-             , std::enable_if_t<std::disjunction_v<
-                is_curried<std::decay_t<G>>,
-                is_curried<std::decay_t<F>>>, int> = 0 >
-    constexpr auto operator|(G&& g, F&& f) {
-        constexpr bool gc = is_curried_v<std::decay_t<G>>;
-        constexpr bool fc = is_curried_v<std::decay_t<F>>;
-
-        if constexpr ( gc && fc ) {
-            return fpipe(std::forward<G>(g), std::forward<F>(f));
-        }
-
-        if constexpr ( gc && !fc) {
-            return std::forward<G>(g)(std::forward<F>(f));
-        }
-
-        if constexpr ( !gc && fc) {
-            return std::forward<F>(f)(std::forward<G>(g));
-        }
-
-        static_assert(gc || fc, "F or G or both arguments should be curried");
-    }
-
-    //
-    // fcompose operators
-    //
-
-    template < typename G, typename F
-             , std::enable_if_t<std::disjunction_v<
-                is_curried<std::decay_t<G>>,
-                is_curried<std::decay_t<F>>>, int> = 0 >
-    constexpr auto operator*(G&& g, F&& f) {
-        constexpr bool gc = is_curried_v<std::decay_t<G>>;
-        constexpr bool fc = is_curried_v<std::decay_t<F>>;
-
-        if constexpr ( gc && fc ) {
-            return fcompose(std::forward<G>(g), std::forward<F>(f));
-        }
-
-        if constexpr ( gc && !fc) {
-            return std::forward<G>(g)(std::forward<F>(f));
-        }
-
-        if constexpr ( !gc && fc) {
-            return std::forward<F>(f)(std::forward<G>(g));
-        }
-
-        static_assert(gc || fc, "F or G or both arguments should be curried");
-    }
-}
-
-namespace kari_hpp::underscore
-{
-    struct us_t {};
-    inline constexpr us_t _{};
-
-    //
-    // is_underscore, is_underscore_v
-    //
-
-    template < typename T >
-    struct is_underscore
-    : std::bool_constant<std::is_same_v<us_t, std::remove_cv_t<T>>> {};
-
-    template < typename T >
-    inline constexpr bool is_underscore_v = is_underscore<T>::value;
-
-    //
-    // unary operators
-    //
-
-    #define KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP(op, func)\
-        constexpr auto operator op (us_t) {\
-            return curry(func);\
-        }
-
-        KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP(-, std::negate<>())
-        KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP(~, std::bit_not<>())
-        KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP(!, std::logical_not<>())
-    #undef KARI_HPP_DEFINE_UNDERSCORE_UNARY_OP
-
-    //
-    // binary operators
-    //
-
-    #define KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(op, func)\
-        constexpr auto operator op (us_t, us_t) {\
-            return curry(func);\
-        }\
-        \
-        template < typename A, std::enable_if_t<!is_underscore_v<std::decay_t<A>>, int> = 0 >\
-        constexpr auto operator op (A&& a, us_t) {\
-            return curry(func, std::forward<A>(a));\
-        }\
-        \
-        template < typename B, std::enable_if_t<!is_underscore_v<std::decay_t<B>>, int> = 0 >\
-        constexpr auto operator op (us_t, B&& b) {\
-            return fflip(func, std::forward<B>(b));\
-        }
-
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(+ , std::plus<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(- , std::minus<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(* , std::multiplies<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(/ , std::divides<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(% , std::modulus<>())
-
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(< , std::less<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(> , std::greater<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(<=, std::less_equal<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(>=, std::greater_equal<>())
-
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(==, std::equal_to<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(!=, std::not_equal_to<>())
-
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(| , std::bit_or<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(& , std::bit_and<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(^ , std::bit_xor<>())
-
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(||, std::logical_or<>())
-        KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP(&&, std::logical_and<>())
-    #undef KARI_HPP_DEFINE_UNDERSCORE_BINARY_OP
-}
diff --git a/untests/kari_ext_tests.cpp b/untests/kari_ext_tests.cpp
index 4cf04da..a805fe0 100644
--- a/untests/kari_ext_tests.cpp
+++ b/untests/kari_ext_tests.cpp
@@ -4,10 +4,11 @@
  * Copyright (C) 2017-2020, by Matvey Cherevko (blackmatov@gmail.com)
  ******************************************************************************/
 
-#include <kari.hpp/kari_ext.hpp>
+#include <kari.hpp/kari.hpp>
 #include "doctest/doctest.hpp"
 
 using namespace kari_hpp;
+using namespace kari_hpp::ext;
 
 TEST_CASE("kari_ext") {
     struct box final {