diff --git a/examples/str_exam.cpp b/examples/str_exam.cpp
index 4aa1bca..8a29a16 100644
--- a/examples/str_exam.cpp
+++ b/examples/str_exam.cpp
@@ -1,12 +1,16 @@
+#include <list>
 #include <print>
+
 // #include "../utils/snplib_string.h"
 // #include "../include/snipplib/snplib_string.h"
+#include <snipplib/utils/snplib_keyvalue.h>
 #include <snipplib/utils/snplib_string.h>
 
 using namespace snplib;
 int main()
 {
     std::string si = "   dewf wek e    lwekjflkj  ";
+    std::println("s = '{}'", si);
 
     auto s = snplib_trim_spaces(si);
 
@@ -24,6 +28,15 @@ int main()
 
     std::println("sv(TrimType::TRIM_BOTH) = '{}'", sv);
 
+    const char cstr[] = "  dwelkj 3827 dwjh     2398    ";
+    std::println("C-ish string: '{}'", cstr);
+    std::println("C-ish(TrimType::TRIM_BOTH) = '{}'", snplib_trim_spaces_as_view(cstr));
+
+    std::list ll{' ', ' ', '2', ' ', 'e', '4', 's', ' ', ' '};
+    std::println("std::list: {}", ll);
+    std::println("std::ranges::subrange(TrimType::TRIM_BOTH) = '{}'", snplib_trim_spaces_as_view(ll));
+    // std::println("std::ranges::subrange(TrimType::TRIM_BOTH) = '{}'",
+    // std::views::all(snplib_trim_spaces_as_view(ll)));
 
     si = "123; we; d34534; ";
 
@@ -32,16 +45,45 @@ int main()
 
     std::println("\n\nstr = '{}'", si);
 
-    std::println("all elems: ");
+    std::print("all elems: ");
     for (auto& el : rv) {
-        std::println("el = '{}'", el);
+        std::print("'{}'  ", el);
     }
+    std::println("");
 
     rv = snplib_split_char_range<decltype(rv)>(si, "; ", 1, 2);
-    std::println("2 elems starting from 1: ");
+    std::print("2 elems starting from 1: ");
     for (auto& el : rv) {
-        std::println("el = '{}'", el);
+        std::print("'{}'  ", el);
     }
+    std::println("");
+
+
+    si = "  ATTR    AAA 1.1 23 45 09   ";
+    std::vector v{std::from_range, si};
+    ll = {std::from_range, si};
+
+    snplib_keyvalue_t kv{v};
+
+    std::println("\n\nKV = {}", v);
+    std::println("key = '{}'", kv.key());
+    std::println("value = '{}'", kv.value());
+    std::println("valueSeq = '{}'", kv.valueSeq());
+    std::println("valueJoinSeq = '{}'", kv.valueJoinSeq<std::string_view>(3, 3));
+    std::println("valueJoinSeq = '{}'", kv.valueJoinSeq<std::string_view>(3, 30));
+    kv.setKeyValue("VAL", std::make_tuple(1, std::string{"RRR"}, 10.24));
+    std::println("\n\nKV = {}", v);
+
+    snplib_keyvalue_t kvl{ll};
+
+    std::println("\n\nKV = {}", ll);
+    std::println("key = '{}'", kvl.key());
+    std::println("key = '{}'", kvl.key<std::string>());
+    std::println("value = '{}'", kvl.value());
+    std::println("valueSeq = '{}'", kvl.valueSeq());
+    std::println("valueSeq = '{}'", kvl.valueSeq<std::list<std::string>>());
+
+
 
     return 0;
 }
\ No newline at end of file
diff --git a/include/snipplib/concepts/snplib_concepts.h b/include/snipplib/concepts/snplib_concepts.h
index 504672a..9bcca7a 100644
--- a/include/snipplib/concepts/snplib_concepts.h
+++ b/include/snipplib/concepts/snplib_concepts.h
@@ -127,7 +127,7 @@ template <typename T>
 concept snplib_error_c = std::constructible_from<T> && requires(T&& t) {
     static_cast<bool>(std::forward<T>(t));
 
-    { !std::forward<T>(t) } -> std::convertible_to<bool>;
+    // { !std::forward<T>(t) } -> std::convertible_to<bool>;
 };
 
 // utility function to deduce error-type
diff --git a/include/snipplib/serialization/snplib_serialization.h b/include/snipplib/serialization/snplib_serialization.h
index e6535fb..23cfa9a 100644
--- a/include/snipplib/serialization/snplib_serialization.h
+++ b/include/snipplib/serialization/snplib_serialization.h
@@ -214,6 +214,16 @@ struct snplib_deserializer_error_category_t : public std::error_category {
 };
 
 
+inline std::error_code make_error_code(snplib_serializer_error_e ec)
+{
+    return std::error_code(static_cast<int>(ec), snplib_serializer_error_category_t::get());
+}
+
+inline std::error_code make_error_code(snplib_deserializer_error_e ec)
+{
+    return std::error_code(static_cast<int>(ec), snplib_deserializer_error_category_t::get());
+}
+
 
 /*                          BASE SERIALIZER CLASS (FOR IMPLEMENTATIONS BELOW)    */
 
@@ -370,7 +380,7 @@ struct snplib_serializer_t : snplib_serializer_base_t {
                 return snplib_serializer_base_t::serializeRange<value_t>(sr, value, output, params);
             }
         } else if constexpr (snplib_tuple_like_c<VT>) {
-            return [&output, &params]<size_t I = 0>(this auto& self, VT& tp) -> error_t {
+            return [&output, &params]<size_t I = 0>(this auto&& self, VT const& tp) -> error_t {
                 if constexpr (I < (std::tuple_size_v<VT> - 1)) {
                     auto err = snplib_serializer_t<std::tuple_element_t<I, VT>>{}(output, std::get<I>(tp), params);
                     if (err) {
@@ -379,8 +389,9 @@ struct snplib_serializer_t : snplib_serializer_base_t {
 
                     snplib_serializer_base_t::addElemDelimiter(output, params);
 
-                    return self.template operator()<I + 1>(tp);
-                } else if constexpr (I < (std::tuple_size_v<VT> - 1)) {  // the last element
+                    return std::forward<decltype(self)>(self).template operator()<I + 1>(tp);
+                    // } else if constexpr (I < (std::tuple_size_v<VT> - 1)) {  // the last element
+                } else {  // the last element
                     auto err = snplib_serializer_t<std::tuple_element_t<I, VT>>{}(output, std::get<I>(tp), params);
                     if (err) {
                         return snplib_deduced_error(err, snplib_serializer_error_e::ERROR_UNDERLYING_SERIALIZER);
diff --git a/include/snipplib/utils/snplib_keyvalue.h b/include/snipplib/utils/snplib_keyvalue.h
index 7295a76..6293e83 100644
--- a/include/snipplib/utils/snplib_keyvalue.h
+++ b/include/snipplib/utils/snplib_keyvalue.h
@@ -11,11 +11,12 @@ concept snplib_serializable_c =
     requires { []<typename VT>(std::type_identity<VT>) {}(std::type_identity<std::remove_cvref_t<T>>{}); };
 
 template <snplib_char_range_c ByteSeqT>
+    requires(std::ranges::viewable_range<ByteSeqT> && !std::ranges::borrowed_range<ByteSeqT>)
 class snplib_keyvalue_t
 {
 public:
     static constexpr bool mutableContent = snplib_output_char_range_c<ByteSeqT>;
-    static constexpr bool stringViewContent =
+    static constexpr bool contiguousContent =
         std::ranges::viewable_range<ByteSeqT> && std::ranges::contiguous_range<ByteSeqT>;
 
     typedef std::error_code error_t;
@@ -28,79 +29,100 @@ public:
         std::string_view valseq_delim{DEFAULT_VALSEQ_DELIM_SEQ};
     };
 
-    constexpr snplib_keyvalue_t(ByteSeqT&& bytes, config_t cfg = config_t{}) {}
+    constexpr snplib_keyvalue_t(ByteSeqT& bytes, config_t cfg = config_t{}) : _byteSeq(bytes), _config(cfg)
+    {
+        fromByteSequence(bytes, cfg);
+    }
 
     virtual ~snplib_keyvalue_t() = default;
 
-    template <snplib_char_range_c R>
-        requires mutableContent
-    error_t fromByteSequence(R&& bytes)
+    error_t fromByteSequence(ByteSeqT& bytes, config_t cfg = config_t{})
     {
+        _byteSeq = bytes;
+        _config = cfg;
+
         // key and value
 
-        if constexpr (stringViewContent) {
-            auto bs = snplib_trim_spaces_as_view(bytes, TrimType::TRIM_LEFT);
-            auto found = std::ranges::search(bs, _config.keyval_delim);
+        auto bs = snplib_trim_spaces_as_view(bytes, TrimType::TRIM_LEFT);
+        auto found = std::ranges::search(bs, _config.keyval_delim);
 
-            if (found.empty()) {  // no value
-                _key = snplib_trim_spaces_as_view(bs, TrimType::TRIM_RIGHT);
+        if (found.empty()) {  // no value
+            _key = snplib_trim_spaces_as_view(bs, TrimType::TRIM_RIGHT);
 
-                _value = std::string_view();
-            } else {
-                _key = snplib_trim_spaces_as_view(std::string_view(bs.begin(), found.begin()), TrimType::TRIM_RIGHT);
+            _value = decltype(_value)();
+        } else {
+            _key = snplib_trim_spaces_as_view(decltype(_key)(bs.begin(), found.begin()), TrimType::TRIM_RIGHT);
 
-                // do not delete space at the end of value-string!
-                _value = std::string_view(found.end(), bs.end());
-            }
-
-        } else if constexpr (std::ranges::viewable_range<R>) {
-            auto bs = bytes | std::views::drop_while(snplib_is_space);
-            auto found = std::ranges::search(bs, _config.keyval_delim);
-
-            _value.clear();
-
-            if (found.empty()) {  // no  value
-                _key = snplib_trim_spaces(bs, TrimType::TRIM_RIGHT);
-            } else {
-                _key.clear();
-                auto N = std::ranges::distance(bs.begin(), found.begin());
-                std::ranges::copy(std::views::all(bs) | std::views::take(N) | std::views::reverse |
-                                      std::views::drop_while(snplib_is_space),
-                                  std::back_inserter(_key));
-
-                std::ranges::copy(found.end(), bs.end(), std::back_inserter(_value));
-            }
-        } else {  // always coping
-            auto bs = snplib_trim_spaces(bytes, TrimType::TRIM_LEFT);
-            auto found = std::ranges::search(bs, _config.keyval_delim);
-
-            _value.clear();
-
-            if (found.empty()) {  // no  value
-                _key = snplib_trim_spaces(bs, TrimType::TRIM_RIGHT);
-            } else {
-                _key.clear;
-                auto N = std::ranges::distance(bs.begin(), found.begin());
-                // std::ranges::copy_n(bs.begin(), N, std::back_inserter(_key));
-
-                size_t i = 0;
-                for (auto it = bs.begin(); it != found.begin(); ++it, ++i) {
-                    if (i < N) {
-                        if (!snplib_is_space(*it)) {
-                            std::back_inserter(_key) = *it;
-                        }
-                    }
-                }
-            }
-
-            std::ranges::copy(found.end(), bs.end(), std::back_inserter(_value));
+            // do not delete space at the end of value-string!
+            _value = decltype(_value)(found.end(), bs.end());
         }
 
+
+        // if constexpr (contiguousContent) {
+        //     auto bs = snplib_trim_spaces_as_view(bytes, TrimType::TRIM_LEFT);
+        //     auto found = std::ranges::search(bs, _config.keyval_delim);
+
+        //     if (found.empty()) {  // no value
+        //         _key = snplib_trim_spaces_as_view(bs, TrimType::TRIM_RIGHT);
+
+        //         _value = std::string_view();
+        //     } else {
+        //         _key = snplib_trim_spaces_as_view(std::string_view(bs.begin(), found.begin()), TrimType::TRIM_RIGHT);
+
+        //         // do not delete space at the end of value-string!
+        //         _value = std::string_view(found.end(), bs.end());
+        //     }
+
+        // } else if constexpr (std::ranges::viewable_range<R>) {
+        //     auto bs = bytes | std::views::drop_while(snplib_is_space);
+        //     auto found = std::ranges::search(bs, _config.keyval_delim);
+
+        //     _value.clear();
+
+        //     if (found.empty()) {  // no  value
+        //         _key = snplib_trim_spaces(bs, TrimType::TRIM_RIGHT);
+        //     } else {
+        //         _key.clear();
+        //         auto N = std::ranges::distance(bs.begin(), found.begin());
+        //         std::ranges::copy(std::views::all(bs) | std::views::take(N) | std::views::reverse |
+        //                               std::views::drop_while(snplib_is_space),
+        //                           std::back_inserter(_key));
+
+        //         std::ranges::copy(found.end(), bs.end(), std::back_inserter(_value));
+        //     }
+        // } else {  // always coping
+        //     auto bs = snplib_trim_spaces(bytes, TrimType::TRIM_LEFT);
+        //     auto found = std::ranges::search(bs, _config.keyval_delim);
+
+        //     _value.clear();
+
+        //     if (found.empty()) {  // no  value
+        //         _key = snplib_trim_spaces(bs, TrimType::TRIM_RIGHT);
+        //     } else {
+        //         _key.clear;
+        //         auto N = std::ranges::distance(bs.begin(), found.begin());
+        //         // std::ranges::copy_n(bs.begin(), N, std::back_inserter(_key));
+
+        //         size_t i = 0;
+        //         for (auto it = bs.begin(); it != found.begin(); ++it, ++i) {
+        //             if (i < N) {
+        //                 if (!snplib_is_space(*it)) {
+        //                     std::back_inserter(_key) = *it;
+        //                 }
+        //             }
+        //         }
+        //     }
+
+        //     std::ranges::copy(found.end(), bs.end(), std::back_inserter(_value));
+        // }
+
         // split value to elements
 
-        if (_value.size()) {
+        if (!_value.empty()) {
             _valueSeq = snplib_split_char_range<decltype(_valueSeq)>(_value, _config.valseq_delim);
         }
+
+        return {};
     }
 
     template <snplib_char_range_c R>
@@ -109,9 +131,9 @@ public:
         return snplib_transform_char_range<R>(_key);
     }
 
-    constexpr std::string_view key() const
+    constexpr auto key() const
     {
-        return key<std::string_view>();
+        return _key;
     }
 
     template <snplib_char_range_c R>
@@ -120,9 +142,9 @@ public:
         return snplib_transform_char_range<R>(_value);
     }
 
-    constexpr std::string_view value() const
+    constexpr auto value() const
     {
-        return value<std ::string_view>();
+        return _value;
     }
 
 
@@ -147,9 +169,11 @@ public:
             std::ranges::for_each(elems, [&res](auto const& e) {
                 if constexpr (std::constructible_from<el_t, std::string_view::const_iterator,
                                                       std::string_view::const_iterator>) {
-                    std::back_inserter(el_t{e.cbegin(), e.cend()}, std::back_inserter(res));
+                    // std::back_inserter(el_t{e.cbegin(), e.cend()}, std::back_inserter(res));
+                    std::back_inserter(res) = el_t{e.cbegin(), e.cend()};
                 } else if constexpr (std::constructible_from<el_t, std::string_view>) {
-                    std::back_inserter(el_t{e}, std::back_inserter(res));
+                    // std::back_inserter(el_t{e}, std::back_inserter(res));
+                    std::back_inserter(res) = el_t{e};
                 } else {
                     static_assert(false, "Incompatible types: cannot create output element!");
                 }
@@ -159,9 +183,11 @@ public:
         return res;
     }
 
-    std::vector<std::string_view> valueSeq(size_t start = 0, size_t N = std::numeric_limits<size_t>::max()) const
+    auto valueSeq(size_t start = 0, size_t N = std::numeric_limits<size_t>::max()) const
+    // std::vector<std::string_view> valueSeq(size_t start = 0, size_t N = std::numeric_limits<size_t>::max()) const
     {
-        return valueSeq<std::vector<std::string_view>>(start, N);
+        // return valueSeq<std::vector<std::string_view>>(start, N);
+        return _valueSeq;
     }
 
 
@@ -172,7 +198,7 @@ public:
             return OR();
         }
 
-        auto last_idx = start + N;
+        auto last_idx = start + N - 1;
         if (last_idx >= _valueSeq.size()) {
             last_idx = _valueSeq.size() - 1;
         }
@@ -197,24 +223,30 @@ public:
         requires mutableContent
     error_t setKey(KeyT&& key, SParT const& sparams = snplib_serialization_params_t{})
     {
-        auto err = snplib_serializer_t<std::remove_cvref_t<KeyT>>(_key, std::forward<KeyT>(key), sparams);
+        _byteSeq.clear();
+        auto err = snplib_serializer_t<std::remove_cvref_t<KeyT>>{}(_byteSeq, std::forward<KeyT>(key), sparams);
         if (err) {
-            return snplib_deduced_error(err, std::errc::invalid_argument);
+            // return snplib_deduced_error(err, std::errc::invalid_argument);
+            // return snplib_deduced_error(err, std::make_error_code(std::errc::invalid_argument));
+            return std::make_error_code(std::errc::invalid_argument);
         }
 
         return {};
+        // return std::make_error_code(std::errc{});
     }
 
     template <snplib_serializable_c ValueT, snplib_serialization_params_c SParT = snplib_serialization_params_t>
         requires mutableContent
     error_t setValue(ValueT&& value, SParT const& sparams = snplib_serialization_params_t{})
     {
-        auto err = snplib_serializer_t<std::remove_cvref_t<ValueT>>(_key, std::forward<ValueT>(value), sparams);
+        auto err = snplib_serializer_t<std::remove_cvref_t<ValueT>>{}(_byteSeq, std::forward<ValueT>(value), sparams);
         if (err) {
-            return snplib_deduced_error(err, std::errc::invalid_argument);
+            // return snplib_deduced_error(err, std::make_error_code(std::errc::invalid_argument));
+            return std::make_error_code(std::errc::invalid_argument);
         }
 
         return {};
+        // return std::make_error_code(std::errc{});
     }
 
 
@@ -229,22 +261,25 @@ public:
             return err;
         }
 
-        return setValue(std::forward<KeyT>(value), sparams);
+        return setValue(std::forward<ValueT>(value), sparams);
     }
 
 protected:
-    std::
-        conditional_t<mutableContent, std::string, std::conditional_t<stringViewContent, std::string_view, std::string>>
-            _key;
-    std::
-        conditional_t<mutableContent, std::string, std::conditional_t<stringViewContent, std::string_view, std::string>>
-            _value;
-    std::vector<std::string_view> _valueSeq;
-    // std::conditional_t<mutableContent,
-    //                    std::vector<std::string>,
-    //                    std::conditional_t<stringViewContent, std::vector<std::string_view>,
-    //                    std::vector<std::string>>>
-    // _valueSeq;
+    ByteSeqT& _byteSeq;
+
+    // std::
+    //     conditional_t<mutableContent, std::string, std::conditional_t<contiguousContent, std::string_view,
+    //     std::string>>
+    //         _key;
+    // std::
+    //     conditional_t<mutableContent, std::string, std::conditional_t<contiguousContent, std::string_view,
+    //     std::string>>
+    //         _value;
+    std::conditional_t<contiguousContent, std::string_view, std::ranges::subrange<typename ByteSeqT::iterator>> _key;
+    std::conditional_t<contiguousContent, std::string_view, std::ranges::subrange<typename ByteSeqT::iterator>> _value;
+    // std::conditional_t<contiguousContent, std::string_view, std::views::all_t<ByteSeqT>> _key;
+    // std::conditional_t<contiguousContent, std::string_view, std::views::all_t<ByteSeqT>> _value;
+    std::vector<decltype(_value)> _valueSeq;
 
     config_t _config;
 };
diff --git a/include/snipplib/utils/snplib_string.h b/include/snipplib/utils/snplib_string.h
index 296bc90..189658d 100644
--- a/include/snipplib/utils/snplib_string.h
+++ b/include/snipplib/utils/snplib_string.h
@@ -15,7 +15,7 @@ constexpr static bool snplib_is_space(char in) noexcept
 };
 
 
-enum class TrimType { TRIM_LEFT, TRIM_RIGHT, TRIM_BOTH };
+enum class TrimType { TRIM_LEFT = 0b1, TRIM_RIGHT = 0b10, TRIM_BOTH = 0b11 };
 
 template <snplib_output_char_range_c OR, snplib_input_char_range_c R, typename IsSpaceFuncT = decltype(snplib_is_space)>
 constexpr static OR snplib_trim_spaces(R&& r,
@@ -45,38 +45,72 @@ constexpr static std::string snplib_trim_spaces(R&& r,
     return snplib_trim_spaces<std::string>(std::forward<R>(r), type, std::forward<IsSpaceFuncT>(is_space_func));
 }
 
-template <snplib_input_char_range_c R, typename IsSpaceFuncT = decltype(snplib_is_space)>
-constexpr static std::string_view snplib_trim_spaces_as_view(R&& r,
-                                                             TrimType type = TrimType::TRIM_BOTH,
-                                                             IsSpaceFuncT&& is_space_func = snplib_is_space)
-    requires std::ranges::contiguous_range<R>
+// template <snplib_input_char_range_c R, typename IsSpaceFuncT = decltype(snplib_is_space)>
+// constexpr static std::string_view snplib_trim_spaces_as_view(R&& r,
+//                                                              TrimType type = TrimType::TRIM_BOTH,
+//                                                              IsSpaceFuncT&& is_space_func = snplib_is_space)
+//     requires std::ranges::contiguous_range<R>
+// {
+//     auto end = std::forward<R>(r).end();
+
+//     auto f1 = std::forward<R>(r).begin();
+
+//     if (type != TrimType::TRIM_RIGHT) {
+//         // look for the first non-space symbol
+//         f1 = std::ranges::find_if_not(std::forward<R>(r), std::forward<IsSpaceFuncT>(is_space_func));
+//         if (f1 == end) {  // all are spaces!
+//             return std::string_view();
+//         }
+//     }
+
+//     auto f2 = end;
+
+//     if (type != TrimType::TRIM_LEFT) {
+//         auto f3 = f1;
+
+//         do {
+//             f2 = std::ranges::find_if(++f3, end, std::forward<IsSpaceFuncT>(is_space_func));
+//             if (f2 == end)
+//                 break;
+//             f3 = std::ranges::find_if_not(f2 + 1, end, std::forward<IsSpaceFuncT>(is_space_func));
+//         } while (f3 != end);
+//     }
+
+//     return std::string_view(f1, f2);
+// }
+
+
+template <std::ranges::viewable_range R, typename IsSpaceFuncT = decltype(snplib_is_space)>
+    requires(snplib_char_range_c<R> && std::ranges::borrowed_range<R>)
+constexpr static auto snplib_trim_spaces_as_view(R&& r,
+                                                 TrimType type = TrimType::TRIM_BOTH,
+                                                 IsSpaceFuncT&& is_space_func = snplib_is_space)
 {
-    auto end = std::forward<R>(r).end();
+    if constexpr (std::is_pointer_v<std::decay_t<R>>) {  // char*, const char*, char[] ('\0' terminates C-ish string)
+        return snplib_trim_spaces_as_view(std::string_view(std::forward<R>(r)), type,
+                                          std::forward<IsSpaceFuncT>(is_space_func));
+    } else {
+        auto it_left = r.begin();
+        auto it_right = r.end();
 
-    auto f1 = std::forward<R>(r).begin();
+        if (std::to_underlying(type) & std::to_underlying(TrimType::TRIM_LEFT)) {
+            it_left = std::ranges::find_if_not(std::forward<R>(r), std::forward<IsSpaceFuncT>(is_space_func));
+        }
 
-    if (type != TrimType::TRIM_RIGHT) {
-        // look for the first non-space symbol
-        f1 = std::ranges::find_if_not(std::forward<R>(r), std::forward<IsSpaceFuncT>(is_space_func));
-        if (f1 == end) {  // all are spaces!
-            return std::string_view();
+        if (std::to_underlying(type) & std::to_underlying(TrimType::TRIM_RIGHT)) {
+            auto found = std::ranges::find_last_if_not(std::forward<R>(r), std::forward<IsSpaceFuncT>(is_space_func));
+            if (!found.empty()) {
+                it_right = std::next(found.begin());
+            }
+        }
+
+        if constexpr (std::ranges::contiguous_range<std::decay_t<R>>) {
+            return std::string_view{it_left, it_right};
+        } else {
+            return std::ranges::subrange{it_left, it_right};
+            // return std::views::all_t<std::decay_t<R>>(std::ranges::subrange{it_left, it_right});
         }
     }
-
-    auto f2 = end;
-
-    if (type != TrimType::TRIM_LEFT) {
-        auto f3 = f1;
-
-        do {
-            f2 = std::ranges::find_if(++f3, end, std::forward<IsSpaceFuncT>(is_space_func));
-            if (f2 == end)
-                break;
-            f3 = std::ranges::find_if_not(f2 + 1, end, std::forward<IsSpaceFuncT>(is_space_func));
-        } while (f3 != end);
-    }
-
-    return std::string_view(f1, f2);
 }
 
 
@@ -113,13 +147,21 @@ static constexpr OR snplib_transform_char_range(IR&& r, CTorTs&&... or_ctor_args
 {
     using val_t = std::remove_cvref_t<IR>;
 
+    static constexpr bool ret_view = snplib_char_view_c<OR> && std::ranges::viewable_range<val_t>;
+
     if constexpr (std::same_as<OR, val_t>) {  // just a copy
         return r;
-    } else if constexpr (snplib_char_view_c<OR> && std::ranges::viewable_range<val_t>) {
+    } else if constexpr (ret_view &&
+                         (std::constructible_from<OR, std::ranges::iterator_t<val_t>, std::ranges::iterator_t<val_t>> ||
+                          std::constructible_from<OR, std::ranges::iterator_t<val_t>,
+                                                  std::ranges::sentinel_t<val_t>>)) {
         return OR{r.begin(), r.end()};
-    } else if (snplib_output_char_range_c<OR>) {
+    } else if constexpr (std::constructible_from<OR, val_t>) {
+        return OR(std::forward<IR>(r));
+    } else if constexpr (snplib_output_char_range_c<OR>) {
         OR res(std::forward<CTorTs>(or_ctor_args)...);
         std::ranges::copy(std::forward<IR>(r), std::back_inserter(res));
+        return res;
     } else {
         static_assert(false, "Incompatible types!");
     }
@@ -154,8 +196,10 @@ static constexpr OR snplib_split_char_range(IR&& input,
 
         using el_t = std::ranges::range_value_t<OR>;
         using it_t = std::ranges::iterator_t<IR>;
-        static_assert(std::constructible_from<el_t, it_t, it_t>,
+        static_assert(std::constructible_from<el_t, decltype(input.begin()), decltype(input.end())>,
                       "Incompatible input and output types: cannot create element!");
+        // static_assert(std::constructible_from<el_t, it_t, it_t>,
+        //               "Incompatible input and output types: cannot create element!");
 
         auto it = input.begin();