diff --git a/examples/hmap_example.cpp b/examples/hmap_example.cpp
index 581031f..fc1dcec 100644
--- a/examples/hmap_example.cpp
+++ b/examples/hmap_example.cpp
@@ -162,5 +162,66 @@ int main()
         }
     }
 
+
+    std::println("\n\n\n\n");
+
+    snplib::hmap<std::string> hm;
+
+    std::string k1{"k_int"}, k2{"k_str"}, k3("k_dbl");
+    int i1 = 10;
+    double f1 = 7.7;
+    std::string s1 = "test-str";
+
+    std::print("push element with key '{}' and value {}\t...", k1, i1);
+    ok = hm.push(k1, i1, std::tuple<long, double, float, long long>{});
+    if (!ok) {
+        std::println("cannot insert the value {}", i1);
+    } else {
+        std::println("OK");
+    }
+
+    std::print("push element with key '{}' and value {}\t...", k2, s1);
+    ok = hm.push(
+        k2, s1,
+        [](auto const& v) -> decltype(hm)::hmap_expected_t<const char*> {
+            return v.c_str();
+            // if (v) {
+            //     return v.c_str();
+            // } else {
+            //     return std::unexpected(v.error());
+            // }
+        },
+        [](auto const& v) -> decltype(hm)::hmap_expected_t<std::string> {
+            return std::string(v.value());
+            // if (v) {
+            //     return std::string(v.value());
+            // } else {
+            //     return std::unexpected(v.error());
+            // }
+        });
+    if (!ok) {
+        std::println("cannot insert the value {}", s1);
+    } else {
+        std::println("OK");
+    }
+
+    std::print("push element with key '{}' and value {}\t...", k3, f1);
+    ok = hm.push(k3, f1, std::tuple<long, int, float, long long>{});
+    if (!ok) {
+        std::println("cannot insert the value {}", f1);
+    } else {
+        std::println("OK");
+    }
+
+    std::println("\n");
+
+    std::print("get '{}'-element as double: ", k1);
+    auto f2 = hm.get<double>(k1);
+    if (f2) {
+        std::println("{}", f2.value());
+    } else {
+        std::println("FAIL");
+    }
+
     return 0;
 }
\ No newline at end of file
diff --git a/include/snipplib/containers/snplib_hmap.h b/include/snipplib/containers/snplib_hmap.h
index 2dbd23f..121d249 100644
--- a/include/snipplib/containers/snplib_hmap.h
+++ b/include/snipplib/containers/snplib_hmap.h
@@ -454,64 +454,34 @@ protected:
     inline static std::vector<std::function<bool(KeyT const&, const hmap*)>> _containsFunc{};
 
 
-    // trivial conversional functors
-    struct trivial_conv_from_t {
-        hmap const* obj;
-        KeyT const& key;
-
-        template <typename VT, typename UT>
-        hmap_expected_t<UT> operator()(hmap_expected_t<VT> const&)
-        {
-            auto v = obj->get<VT>(key);
-            if (v) {
-                return static_cast<UT>(v.value());
-            }
-
-            return hmap_error_e::ERROR_USER_CONV;
-        }
-    };
-
-    struct trivial_conv_to_t {
-        hmap const* obj;
-        KeyT const& key;
-
-        template <typename VT, typename UT>
-        hmap_expected_t<VT> operator()(hmap_expected_t<UT> const& uval)
-        {
-            if (uval) {
-                auto err = obj->set(key, uval.value());
-                if (err) {
-                    return std::unexpected(err);
-                }
-
-                // return
-            }
-
-            return hmap_error_e::ERROR_USER_CONV;
-        }
-    };
-
+    // trivial conversional functions
 
     template <typename VT, typename UT>
         requires requires(VT v, UT u) { v = u; }
-    inline static std::function<hmap_expected_t<UT>(hmap_expected_t<VT> const&)> trivial_conv_from =
-        [](hmap_expected_t<VT> const& val) -> hmap_expected_t<UT> {
-            if (val) {
-                return static_cast<UT>(val.value());
-            } else {
-                return val.error();
-            }
+    inline static std::function<hmap_expected_t<UT>(VT const&)> trivial_conv_from =
+        [](VT const& val) -> hmap_expected_t<UT> {
+            // inline static std::function<hmap_expected_t<UT>(hmap_expected_t<VT> const&)> trivial_conv_from =
+            // [](hmap_expected_t<VT> const& val) -> hmap_expected_t<UT> {
+            return static_cast<UT>(val);
+            // if (val) {
+            //     return static_cast<UT>(val.value());
+            // } else {
+            //     return val.error();
+            // }
         };
 
     template <typename VT, typename UT>
         requires requires(VT v, UT u) { u = v; }
-    inline static std::function<hmap_expected_t<VT>(hmap_expected_t<UT> const&)> trivial_conv_to =
-        [](hmap_expected_t<UT> const& uval) -> hmap_expected_t<VT> {
-            if (uval) {
-                return static_cast<VT>(uval.value());
-            } else {
-                return uval.error();
-            }
+    inline static std::function<hmap_expected_t<VT>(UT const&)> trivial_conv_to =
+        [](UT const& uval) -> hmap_expected_t<VT> {
+            // inline static std::function<hmap_expected_t<VT>(hmap_expected_t<UT> const&)> trivial_conv_to =
+            //     [](hmap_expected_t<UT> const& uval) -> hmap_expected_t<VT> {
+            return static_cast<VT>(uval);
+            // if (uval) {
+            //     return static_cast<VT>(uval.value());
+            // } else {
+            //     return uval.error();
+            // }
         };
 
 public:
@@ -692,7 +662,7 @@ public:
         }
 
         auto add_cnv_func = [this](KeyT const& kk, auto&& from_cnv_func, auto&& to_cnv_func) {
-            using u_t = std::invoke_result_t<decltype(from_cnv_func), v_t>;
+            using u_t = std::invoke_result_t<decltype(from_cnv_func), v_t>::value_type;
 
             // user type must differ from inserted one
             static_assert(!std::same_as<v_t, u_t>, "INVALID CONVERSIONAL 'FROM-FUNCTION' SIGNATURE!");
@@ -704,16 +674,17 @@ public:
                     return std::forward<decltype(from_cnv_func_arg)>(from_cnv_func_arg)(_values<v_t>[obj][kk]);
                 });
 
-            _setter<u_t>[this].emplace(kk, [kk, to_cnv_func_arg = std::forward<decltype(to_cnv_func)>(to_cnv_func)](
-                                               const u_t& v, const hmap* obj) mutable {
-                auto val = std::forward<decltype(to_cnv_func_arg)>(to_cnv_func_arg)(v);
-                if (val) {
-                    _values<v_t>[obj][kk] = val;
-                    return hmap_error_e::ERROR_OK;
-                } else {
-                    return val.error();
-                }
-            });
+            _setter<u_t>[this].emplace(kk,
+                                       [kk, to_cnv_func_arg = std::forward<decltype(to_cnv_func)>(to_cnv_func)](
+                                           const u_t& v, const hmap* obj) mutable -> hmap::error_t {
+                                           auto val = std::forward<decltype(to_cnv_func_arg)>(to_cnv_func_arg)(v);
+                                           if (val) {
+                                               _values<v_t>[obj][kk] = val.value();
+                                               return hmap_error_e::ERROR_OK;
+                                           } else {
+                                               return val.error();
+                                           }
+                                       });
 
             _clearFunc.emplace_back([](hmap* obj) {
                 _getter<u_t>[obj].clear();
@@ -741,14 +712,15 @@ public:
         requires(sizeof...(Ts) > 0)
     auto push(KeyT const& key, VT&& value, std::tuple<Ts...>)
     {
+        using v_t = std::decay_t<VT>;
         using tp_t = std::tuple<Ts...>;
 
-        return [&key, val = std::forward<VT>(value), this]<size_t... Is>(std::index_sequence<Is...>) {
+        return [&key, val = std::forward<VT>(value), this]<size_t... Is>(std::index_sequence<Is...>) mutable {
             return std::apply([this](auto&&... args) { return push(std::forward<decltype(args)>(args)...); },
                               std::tuple_cat(std::forward_as_tuple(key, std::forward<VT>(val)),
                                              std::tuple_cat(std::forward_as_tuple(
-                                                 hmap::trivial_conv_from<VT, std::tuple_element_t<Is, tp_t>>,
-                                                 hmap::trivial_conv_to<VT, std::tuple_element_t<Is, tp_t>>)...)));
+                                                 hmap::trivial_conv_from<v_t, std::tuple_element_t<Is, tp_t>>,
+                                                 hmap::trivial_conv_to<v_t, std::tuple_element_t<Is, tp_t>>)...)));
         }(std::make_index_sequence<sizeof...(Ts)>{});
     }