refactor: remove name of unused arg in func

docs/content.en/docs/features/value.md

@@ -92,6 +92,32 @@ std::cout << v.at(1);
 
 If the stored type is not `array_type`, a `type_error` is thrown.
 
+### `try_at(std::size_t i)`
+
+Performs the same operation as `at(i)`, but instead of throwing an exception on failure, it always returns a [`toml::result<T&, error_info>`]({{<ref "docs/reference/result">}}). It does not throw an exception on failure.
+
+```cpp
+toml::value v(toml::array{1,2,3});
+
+auto res1 = v.try_at(1);
+assert(res1.is_ok());
+std::cout << res1.unwrap() << std::endl;
+
+auto res5 = v.try_at(5);
+assert(res1.is_err());
+std::cout << toml::format_error(res1.unwrap_err()) << std::endl;
+```
+
+Additionally, since this `toml::result` holds a reference, it is possible to update the value.
+
+```cpp
+toml::value v(toml::array{1,2,3});
+
+auto res1 = v.try_at(1);
+assert(res1.is_ok());
+res1.unwrap() = 42;
+```
+
 #### `at(std::string key)`, `operator[](std::string key)`
 
 These are equivalent to `as_table().at(key)` and `as_table()[key]`.
@@ -105,6 +131,32 @@ v["a"] = 42;
 
 If the stored type is not `table_type`, a `type_error` is thrown.
 
+### `try_at(std::string key)`
+
+Performs the same operation as `at(key)`, but instead of throwing an exception on failure, it always returns a [`toml::result<T&, error_info>`]({{<ref "docs/reference/result">}}). It does not throw an exception on failure.
+
+```cpp
+toml::value v(toml::table{ {"a", 42}, {"b", "foo"} });
+
+auto res_a = v.try_at("a");
+assert(res_a.is_ok());
+std::cout << res_a.unwrap() << std::endl;
+
+auto res_c = v.try_at("c");
+assert(res_c.is_err());
+std::cout << toml::format_error(res_c.unwrap_err()) << std::endl;
+```
+
+Additionally, since this `toml::result` holds a reference, it is possible to update the value.
+
+```cpp
+toml::value v(toml::table{ {"a", 42}, {"b", "foo"} });
+
+auto res_a = v.try_at("a");
+assert(res_a.is_ok());
+res_a.unwrap() = 6 * 9;
+```
+
 #### `size()`
 
 Returns the length.

docs/content.en/docs/reference/value.md

@@ -585,6 +585,27 @@ Throws `std::out_of_range` if the `table` does not contain the specified element
 
 -----
 
+### `try_at(key)`
+
+```cpp
+result<std::reference_wrapper<value_type>,       error_info> try_at(const key_type& key)       noexcept;
+result<std::reference_wrapper<const value_type>, error_info> try_at(const key_type& key) const noexcept;
+```
+
+#### Return Value
+
+After casting the current `value` to a `table`, it returns the element specified by the `key`.
+
+If successful, it returns a `reference_wrapper` holding a reference to that element.
+
+If unsuccessful, it returns an `error_info` corresponding to `type_error` or `out_of_range`.
+
+#### Exceptions
+
+Does not throw.
+
+-----
+
 #### `operator[](key)`
 
 ```cpp
@@ -652,6 +673,26 @@ Throws `toml::type_error` if the stored value is not an `array`.
 
 Throws `std::out_of_range` if the specified element does not exist in the `array`.
 
+-----
+
+### `try_at(idx)`
+
+```cpp
+result<std::reference_wrapper<value_type>,       error_info> try_at(const std::size_t idx)       noexcept;
+result<std::reference_wrapper<const value_type>, error_info> try_at(const std::size_t idx) const noexcept;
+```
+
+#### Return Value
+
+After casting the current `value` to an `array`, it returns the element specified by the `idx`.
+
+If successful, it returns a `reference_wrapper` holding a reference to that element.
+
+If unsuccessful, it returns an `error_info` corresponding to `type_error` or `out_of_range`.
+
+#### Exceptions
+
+Does not throw.
 
 -----
 

docs/content.ja/docs/features/value.md

@@ -96,6 +96,32 @@ std::cout << v.at(1);
 
 格納している型が `array_type` ではなかった場合、 `type_error` を送出します。
 
+#### `try_at(std::size_t i)`
+
+`at(i)`と同様の操作をしますが、失敗時に例外を投げる代わりに、常に[`toml::result<T&, error_info>`]({{<ref "docs/reference/result">}})を返します。失敗時に例外は投げません。
+
+```cpp
+toml::value v(toml::array{1,2,3});
+
+auto res1 = v.try_at(1);
+assert(res1.is_ok());
+std::cout << res1.unwrap() << std::endl;
+
+auto res5 = v.try_at(5);
+assert(res1.is_err());
+std::cout << toml::format_error(res1.unwrap_err()) << std::endl;
+```
+
+また、この`toml::result`は成功値として参照を持つので、値を更新することも可能です。
+
+```cpp
+toml::value v(toml::array{1,2,3});
+
+auto res1 = v.try_at(1);
+assert(res1.is_ok());
+res1.unwrap() = 42;
+```
+
 #### `at(std::string key)`, `operator[](std::string key)`
 
 `as_table().at(key)`, `as_table()[key]` と同等です。
@@ -111,6 +137,32 @@ v["a"] = 42;
 
 格納している型が `table_type` ではなかった場合、 `type_error` を送出します。
 
+#### `try_at(std::string key)`
+
+`at(key)`と同様の操作をしますが、失敗時に例外を投げる代わりに、常に[`toml::result<T&, error_info>`]({{<ref "docs/reference/result">}})を返します。失敗時に例外は投げません。
+
+```cpp
+toml::value v(toml::table{ {"a", 42}, {"b", "foo"} });
+
+auto res_a = v.try_at("a");
+assert(res_a.is_ok());
+std::cout << res_a.unwrap() << std::endl;
+
+auto res_c = v.try_at("c");
+assert(res_c.is_err());
+std::cout << toml::format_error(res_c.unwrap_err()) << std::endl;
+```
+
+また、この`toml::result`は成功値として参照を持つので、値を更新することも可能です。
+
+```cpp
+toml::value v(toml::table{ {"a", 42}, {"b", "foo"} });
+
+auto res_a = v.try_at("a");
+assert(res_a.is_ok());
+res_a.unwrap() = 6 * 9;
+```
+
 #### `size()`
 
 長さを返します。

docs/content.ja/docs/reference/value.md

@@ -583,6 +583,27 @@ value_type const& at(const key_type& key) const;
 
 -----
 
+### `try_at(key)`
+
+```cpp
+result<std::reference_wrapper<value_type>,       error_info> try_at(const key_type& key)       noexcept;
+result<std::reference_wrapper<const value_type>, error_info> try_at(const key_type& key) const noexcept;
+```
+
+#### 戻り値
+
+今の`value`を`table`にキャストしたあと、`key`によって指定される要素を返します。
+
+成功した場合、その要素への参照を持つ`reference_wrapper`を返します。
+
+失敗した場合、 `type_error` または `out_of_range` に対応する `error_info` を返します。
+
+#### 例外
+
+投げません。
+
+-----
+
 #### `operator[](key)`
 
 ```cpp
@@ -652,6 +673,27 @@ value_type const& at(const std::size_t idx) const;
 
 -----
 
+### `try_at(idx)`
+
+```cpp
+result<std::reference_wrapper<value_type>,       error_info> try_at(const std::size_t idx)       noexcept;
+result<std::reference_wrapper<const value_type>, error_info> try_at(const std::size_t idx) const noexcept;
+```
+
+#### 戻り値
+
+今の`value`を`array`にキャストしたあと、`idx`によって指定される要素を返します。
+
+成功した場合、その要素への参照を持つ`reference_wrapper`を返します。
+
+失敗した場合、 `type_error` または `out_of_range` に対応する `error_info` を返します。
+
+#### 例外
+
+投げません。
+
+-----
+
 ### `operator[](idx)`
 
 ```cpp

include/toml11/find.hpp

@@ -4,6 +4,7 @@
 #include <algorithm>
 
 #include "get.hpp"
+#include "utility.hpp"
 #include "value.hpp"
 
 #if defined(TOML11_HAS_STRING_VIEW)
@@ -101,54 +102,7 @@ find(basic_value<TC>&& v, const std::size_t idx)
 }
 
 // --------------------------------------------------------------------------
-// toml::find(toml::value, toml::key, Ts&& ... keys)
-
-namespace detail
-{
-
-// It suppresses warnings by -Wsign-conversion when we pass integer literal
-// to toml::find. integer literal `0` is deduced as an int, and will be
-// converted to std::size_t. This causes sign-conversion.
-
-template<typename TC>
-std::size_t key_cast(const std::size_t& v) noexcept
-{
-    return v;
-}
-template<typename TC, typename T>
-cxx::enable_if_t<std::is_integral<cxx::remove_cvref_t<T>>::value, std::size_t>
-key_cast(const T& v) noexcept
-{
-    return static_cast<std::size_t>(v);
-}
-
-// for string-like (string, string literal, string_view)
-
-template<typename TC>
-typename basic_value<TC>::key_type const&
-key_cast(const typename basic_value<TC>::key_type& v) noexcept
-{
-    return v;
-}
-template<typename TC>
-typename basic_value<TC>::key_type
-key_cast(const typename basic_value<TC>::key_type::value_type* v)
-{
-    return typename basic_value<TC>::key_type(v);
-}
-#if defined(TOML11_HAS_STRING_VIEW)
-template<typename TC>
-typename basic_value<TC>::key_type
-key_cast(const std::string_view v)
-{
-    return typename basic_value<TC>::key_type(v);
-}
-#endif // string_view
-
-} // detail
-
-// ----------------------------------------------------------------------------
-// find(v, keys...)
+// toml::find(toml::value, toml::key, Ts&& ... keys) w/o conversion
 
 template<typename TC, typename K1, typename K2, typename ... Ks>
 cxx::enable_if_t<detail::is_type_config<TC>::value, basic_value<TC>> const&

include/toml11/from.hpp

@@ -7,7 +7,18 @@ namespace toml
 template<typename T>
 struct from;
 // {
-//     static T from_toml(const toml::value& v)
+//     template<typename TC>
+//     static T from_toml(const toml::basic_value<TC>& v)
+//     {
+//         // User-defined conversions ...
+//     }
+// };
+
+template<typename T>
+struct try_from;
+// {
+//     template<typename TC>
+//     static result<T, error_info> try_from_toml(const toml::basic_value<TC>& v) noexcept
 //     {
 //         // User-defined conversions ...
 //     }

include/toml11/result.hpp

@@ -244,13 +244,13 @@ struct result
     {
         if(other.is_ok())
         {
-            auto tmp = ::new(std::addressof(this->succ_)) success_type(other.as_ok());
+            auto tmp = ::new(std::addressof(this->succ_)) success_type(other.succ_);
             assert(tmp == std::addressof(this->succ_));
             (void)tmp;
         }
         else
         {
-            auto tmp = ::new(std::addressof(this->fail_)) failure_type(other.as_err());
+            auto tmp = ::new(std::addressof(this->fail_)) failure_type(other.fail_);
             assert(tmp == std::addressof(this->fail_));
             (void)tmp;
         }
@@ -259,13 +259,13 @@ struct result
     {
         if(other.is_ok())
         {
-            auto tmp = ::new(std::addressof(this->succ_)) success_type(std::move(other.as_ok()));
+            auto tmp = ::new(std::addressof(this->succ_)) success_type(std::move(other.succ_));
             assert(tmp == std::addressof(this->succ_));
             (void)tmp;
         }
         else
         {
-            auto tmp = ::new(std::addressof(this->fail_)) failure_type(std::move(other.as_err()));
+            auto tmp = ::new(std::addressof(this->fail_)) failure_type(std::move(other.fail_));
             assert(tmp == std::addressof(this->fail_));
             (void)tmp;
         }
@@ -276,13 +276,13 @@ struct result
         this->cleanup();
         if(other.is_ok())
         {
-            auto tmp = ::new(std::addressof(this->succ_)) success_type(other.as_ok());
+            auto tmp = ::new(std::addressof(this->succ_)) success_type(other.succ_);
             assert(tmp == std::addressof(this->succ_));
             (void)tmp;
         }
         else
         {
-            auto tmp = ::new(std::addressof(this->fail_)) failure_type(other.as_err());
+            auto tmp = ::new(std::addressof(this->fail_)) failure_type(other.fail_);
             assert(tmp == std::addressof(this->fail_));
             (void)tmp;
         }
@@ -294,13 +294,13 @@ struct result
         this->cleanup();
         if(other.is_ok())
         {
-            auto tmp = ::new(std::addressof(this->succ_)) success_type(std::move(other.as_ok()));
+            auto tmp = ::new(std::addressof(this->succ_)) success_type(std::move(other.succ_));
             assert(tmp == std::addressof(this->succ_));
             (void)tmp;
         }
         else
         {
-            auto tmp = ::new(std::addressof(this->fail_)) failure_type(std::move(other.as_err()));
+            auto tmp = ::new(std::addressof(this->fail_)) failure_type(std::move(other.fail_));
             assert(tmp == std::addressof(this->fail_));
             (void)tmp;
         }

include/toml11/traits.hpp

@@ -90,6 +90,13 @@ struct has_specialized_from_impl
     template<typename T, std::size_t S = sizeof(::toml::from<T>)>
     static std::true_type check(::toml::from<T>*);
 };
+struct has_specialized_try_from_impl
+{
+    template<typename T>
+    static std::false_type check(...);
+    template<typename T, std::size_t S = sizeof(::toml::try_from<T>)>
+    static std::true_type check(::toml::try_from<T>*);
+};
 struct has_specialized_into_impl
 {
     template<typename T>
@@ -130,6 +137,8 @@ template<typename T>
 struct has_specialized_from: decltype(has_specialized_from_impl::check<T>(nullptr)){};
 template<typename T>
 struct has_specialized_into: decltype(has_specialized_into_impl::check<T>(nullptr)){};
+template<typename T>
+struct has_specialized_try_from: decltype(has_specialized_try_from_impl::check<T>(nullptr)){};
 
 #ifdef __INTEL_COMPILER
 #undef decltype

include/toml11/try_find.hpp

@@ -0,0 +1,228 @@
+#ifndef TOML11_TRY_FIND_HPP
+#define TOML11_TRY_FIND_HPP
+
+#include <algorithm>
+
+#include "try_get.hpp"
+#include "utility.hpp"
+#include "value.hpp"
+
+#if defined(TOML11_HAS_STRING_VIEW)
+#include <string_view>
+#endif
+
+namespace toml
+{
+
+// ----------------------------------------------------------------------------
+// find<T>(value, key);
+
+template<typename T, typename TC>
+decltype(try_get<T>(std::declval<basic_value<TC> const&>()))
+try_find(const basic_value<TC>& v, const typename basic_value<TC>::key_type& ky) noexcept
+{
+    const auto res = v.try_at(ky);
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_get<T>(res.as_ok());
+}
+
+template<typename T, typename TC>
+decltype(try_get<T>(std::declval<basic_value<TC>&>()))
+try_find(basic_value<TC>& v, const typename basic_value<TC>::key_type& ky) noexcept
+{
+    auto res = v.try_at(ky);
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_get<T>(res.as_ok());
+}
+
+template<typename T, typename TC>
+decltype(try_get<T>(std::declval<basic_value<TC>&&>()))
+try_find(basic_value<TC>&& v, const typename basic_value<TC>::key_type& ky) noexcept
+{
+    auto res = v.try_at(ky);
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_get<T>(std::move(res.as_ok()));
+}
+
+// ----------------------------------------------------------------------------
+// find<T>(value, idx)
+
+template<typename T, typename TC>
+decltype(try_get<T>(std::declval<basic_value<TC> const&>()))
+try_find(const basic_value<TC>& v, const std::size_t idx) noexcept
+{
+    const auto res = v.try_at(idx);
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_get<T>(res.as_ok());
+}
+template<typename T, typename TC>
+decltype(try_get<T>(std::declval<basic_value<TC>&>()))
+try_find(basic_value<TC>& v, const std::size_t idx) noexcept
+{
+    auto res = v.try_at(idx);
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_get<T>(res.as_ok());
+}
+template<typename T, typename TC>
+decltype(try_get<T>(std::declval<basic_value<TC>&&>()))
+try_find(basic_value<TC>&& v, const std::size_t idx) noexcept
+{
+    auto res = v.try_at(idx);
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_get<T>(std::move(res.as_ok()));
+}
+
+// ----------------------------------------------------------------------------
+// find(value, key/idx), w/o conversion
+
+template<typename TC>
+cxx::enable_if_t<detail::is_type_config<TC>::value,
+    result<std::reference_wrapper<basic_value<TC>>, error_info>>
+try_find(basic_value<TC>& v, const typename basic_value<TC>::key_type& ky) noexcept
+{
+    return v.try_at(ky);
+}
+template<typename TC>
+cxx::enable_if_t<detail::is_type_config<TC>::value,
+    result<std::reference_wrapper<const basic_value<TC>>, error_info>>
+try_find(basic_value<TC> const& v, const typename basic_value<TC>::key_type& ky) noexcept
+{
+    return v.try_at(ky);
+}
+template<typename TC>
+cxx::enable_if_t<detail::is_type_config<TC>::value,
+    result<basic_value<TC>, error_info>>
+try_find(basic_value<TC>&& v, const typename basic_value<TC>::key_type& ky) noexcept
+{
+    auto res = v.try_at(ky);
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return ok(basic_value<TC>(std::move(res.as_ok())));
+}
+
+template<typename TC>
+cxx::enable_if_t<detail::is_type_config<TC>::value,
+    result<std::reference_wrapper<basic_value<TC>>, error_info>>
+try_find(basic_value<TC>& v, const std::size_t idx) noexcept
+{
+    return v.try_at(idx);
+}
+template<typename TC>
+cxx::enable_if_t<detail::is_type_config<TC>::value,
+    result<std::reference_wrapper<const basic_value<TC>>, error_info>>
+try_find(basic_value<TC> const& v, const std::size_t idx) noexcept
+{
+    return v.try_at(idx);
+}
+template<typename TC>
+cxx::enable_if_t<detail::is_type_config<TC>::value,
+    result<basic_value<TC>, error_info>>
+try_find(basic_value<TC>&& v, const std::size_t idx) noexcept
+{
+    auto res = v.try_at(idx);
+    if(res.is_err())
+    {
+        return err(std::move(res.as_err()));
+    }
+    return ok(basic_value<TC>(std::move(res.as_ok())));
+}
+
+// --------------------------------------------------------------------------
+// toml::find(toml::value, toml::key, Ts&& ... keys) w/o conversion
+
+template<typename TC, typename K1, typename K2, typename ... Ks>
+cxx::enable_if_t<detail::is_type_config<TC>::value,
+    result<std::reference_wrapper<const basic_value<TC>>, error_info>>
+try_find(const basic_value<TC>& v, const K1& k1, const K2& k2, const Ks& ... ks) noexcept
+{
+    auto res = v.try_at(detail::key_cast<TC>(k1));
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_find(res.as_ok(), detail::key_cast<TC>(k2), ks...);
+}
+template<typename TC, typename K1, typename K2, typename ... Ks>
+cxx::enable_if_t<detail::is_type_config<TC>::value,
+    result<std::reference_wrapper<basic_value<TC>>, error_info>>
+try_find(basic_value<TC>& v, const K1& k1, const K2& k2, const Ks& ... ks) noexcept
+{
+    auto res = v.try_at(detail::key_cast<TC>(k1));
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_find(res.as_ok(), detail::key_cast<TC>(k2), ks...);
+}
+template<typename TC, typename K1, typename K2, typename ... Ks>
+cxx::enable_if_t<detail::is_type_config<TC>::value,
+    result<basic_value<TC>, error_info>>
+try_find(basic_value<TC>&& v, const K1& k1, const K2& k2, const Ks& ... ks) noexcept
+{
+    auto res = v.try_at(detail::key_cast<TC>(k1));
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_find(std::move(res.as_ok()), detail::key_cast<TC>(k2), ks...);
+}
+
+// ----------------------------------------------------------------------------
+// find<T>(v, keys...)
+
+template<typename T, typename TC, typename K1, typename K2, typename ... Ks>
+decltype(::toml::try_get<T>(std::declval<const basic_value<TC>&>()))
+try_find(const basic_value<TC>& v, const K1& k1, const K2& k2, const Ks& ... ks) noexcept
+{
+    auto res = v.try_at(detail::key_cast<TC>(k1));
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_find<T>(res.as_ok(), detail::key_cast<TC>(k2), ks...);
+}
+template<typename T, typename TC, typename K1, typename K2, typename ... Ks>
+decltype(::toml::try_get<T>(std::declval<basic_value<TC>&>()))
+try_find(basic_value<TC>& v, const K1& k1, const K2& k2, const Ks& ... ks) noexcept
+{
+    auto res = v.try_at(detail::key_cast<TC>(k1));
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_find<T>(res.as_ok(), detail::key_cast<TC>(k2), ks...);
+}
+template<typename T, typename TC, typename K1, typename K2, typename ... Ks>
+decltype(::toml::try_get<T>(std::declval<basic_value<TC>&&>()))
+try_find(basic_value<TC>&& v, const K1& k1, const K2& k2, const Ks& ... ks) noexcept
+{
+    auto res = v.try_at(detail::key_cast<TC>(k1));
+    if(res.is_err())
+    {
+        return err(res.as_err());
+    }
+    return try_find<T>(std::move(res.as_ok()), detail::key_cast<TC>(k2), ks...);
+}
+
+} // toml
+#endif // TOML11_FIND_HPP

include/toml11/try_get.hpp

@@ -0,0 +1,472 @@
+#ifndef TOML11_TRY_GET_HPP
+#define TOML11_TRY_GET_HPP
+
+#include <algorithm>
+
+#include "error_info.hpp"
+#include "from.hpp"
+#include "types.hpp"
+#include "value.hpp"
+
+#if defined(TOML11_HAS_STRING_VIEW)
+#include <string_view>
+#endif // string_view
+
+namespace toml
+{
+
+// ============================================================================
+// T is toml::value; identity transformation.
+
+template<typename T, typename TC>
+cxx::enable_if_t<std::is_same<T, basic_value<TC>>::value,
+    result<std::reference_wrapper<T>, error_info>>
+try_get(basic_value<TC>& v) noexcept
+{
+    return ok(std::ref(v));
+}
+
+template<typename T, typename TC>
+cxx::enable_if_t<std::is_same<T, basic_value<TC>>::value,
+    result<std::reference_wrapper<const T>, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    return ok(std::cref(v));
+}
+
+template<typename T, typename TC>
+cxx::enable_if_t<std::is_same<T, basic_value<TC>>::value,
+    result<T, error_info>>
+try_get(basic_value<TC>&& v) noexcept
+{
+    return ok(basic_value<TC>(std::move(v)));
+}
+
+// ============================================================================
+// exact toml::* type
+
+template<typename T, typename TC>
+cxx::enable_if_t<detail::is_exact_toml_type<T, basic_value<TC>>::value,
+    result<std::reference_wrapper<T>, error_info>>
+try_get(basic_value<TC>& v) noexcept
+{
+    constexpr auto ty = detail::type_to_enum<T, basic_value<TC>>::value;
+    if(v.type() == ty)
+    {
+        return ok(std::ref(detail::getter<TC, ty>::get_nothrow(v)));
+    }
+    else
+    {
+        return err(detail::make_type_error(v, "toml::try_get()", ty));
+    }
+}
+
+template<typename T, typename TC>
+cxx::enable_if_t<detail::is_exact_toml_type<T, basic_value<TC>>::value,
+    result<std::reference_wrapper<const T>, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    constexpr auto ty = detail::type_to_enum<T, basic_value<TC>>::value;
+    if(v.type() == ty)
+    {
+        return ok(std::cref(detail::getter<TC, ty>::get_nothrow(v)));
+    }
+    else
+    {
+        return err(detail::make_type_error(v, "toml::try_get()", ty));
+    }
+}
+
+template<typename T, typename TC>
+cxx::enable_if_t<detail::is_exact_toml_type<T, basic_value<TC>>::value,
+    result<T, error_info>>
+try_get(basic_value<TC>&& v) noexcept
+{
+    constexpr auto ty = detail::type_to_enum<T, basic_value<TC>>::value;
+    if(v.type() == ty)
+    {
+        return ok(detail::getter<TC, ty>::get_nothrow(std::move(v)));
+    }
+    else
+    {
+        return err(detail::make_type_error(v, "toml::try_get()", ty));
+    }
+}
+
+// ============================================================================
+// T is toml::basic_value<U>
+
+template<typename T, typename TC>
+cxx::enable_if_t<cxx::conjunction<
+        detail::is_basic_value<T>,
+        cxx::negation<std::is_same<T, basic_value<TC>>>
+    >::value, result<T, error_info>>
+try_get(basic_value<TC> v) noexcept
+{
+    return ok(T(std::move(v)));
+}
+
+// ============================================================================
+// integer convertible from toml::value::integer_type
+
+template<typename T, typename TC>
+cxx::enable_if_t<cxx::conjunction<
+        std::is_integral<T>,
+        cxx::negation<std::is_same<T, bool>>,
+        detail::is_not_toml_type<T, basic_value<TC>>,
+        cxx::negation<detail::has_from_toml_method<T, TC>>,
+        cxx::negation<detail::has_specialized_from<T>>
+    >::value, result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    if(v.is_integer())
+    {
+        return ok(static_cast<T>(v.as_integer(std::nothrow)));
+    }
+    else
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::integer));
+    }
+}
+
+// ============================================================================
+// floating point convertible from toml::value::floating_type
+
+template<typename T, typename TC>
+cxx::enable_if_t<cxx::conjunction<
+        std::is_floating_point<T>,
+        detail::is_not_toml_type<T, basic_value<TC>>,
+        cxx::negation<detail::has_from_toml_method<T, TC>>,
+        cxx::negation<detail::has_specialized_from<T>>
+    >::value, result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    if(v.is_floating())
+    {
+        return ok(static_cast<T>(v.as_floating(std::nothrow)));
+    }
+    else
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::floating));
+    }
+}
+
+// ============================================================================
+// std::string_view
+
+#if defined(TOML11_HAS_STRING_VIEW)
+
+template<typename T, typename TC>
+cxx::enable_if_t<std::is_same<T, std::string_view>::value,
+    result<std::string_view, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    if(v.is_string())
+    {
+        return ok(std::string_view(v.as_string(std::nothrow)));
+    }
+    else
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::string));
+    }
+}
+
+#endif // string_view
+
+// ============================================================================
+// std::chrono::duration from toml::local_time
+
+template<typename T, typename TC>
+cxx::enable_if_t<detail::is_chrono_duration<T>::value,
+    result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    if(v.is_local_time())
+    {
+        return ok(std::chrono::duration_cast<T>(
+                std::chrono::nanoseconds(v.as_local_time(std::nothrow))));
+    }
+    else
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::local_time));
+    }
+}
+
+// ============================================================================
+// std::chrono::system_clock::time_point from toml::datetime variants
+
+template<typename T, typename TC>
+cxx::enable_if_t<std::is_same<std::chrono::system_clock::time_point, T>::value,
+    result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    switch(v.type())
+    {
+        case value_t::local_date:
+        {
+            return ok(std::chrono::system_clock::time_point(v.as_local_date(std::nothrow)));
+        }
+        case value_t::local_datetime:
+        {
+            return ok(std::chrono::system_clock::time_point(v.as_local_datetime(std::nothrow)));
+        }
+        case value_t::offset_datetime:
+        {
+            return ok(std::chrono::system_clock::time_point(v.as_offset_datetime(std::nothrow)));
+        }
+        default:
+        {
+            const auto loc = v.location();
+            return err(make_error_info("toml::try_get(): bad_cast to "
+                "std::chrono::system_clock::time_point", loc,
+                "the actual type is " + to_string(v.type())));
+        }
+    }
+}
+
+// ============================================================================
+// array-like types; most likely STL container, like std::vector, etc.
+
+template<typename T, typename TC>
+cxx::enable_if_t<cxx::conjunction<
+        detail::is_container<T>,                            // T is a container
+        detail::has_push_back_method<T>,                    // .push_back() works
+        detail::is_not_toml_type<T, basic_value<TC>>,       // but not toml::array
+        cxx::negation<detail::has_from_toml_method<T, TC>>, // no T.from_toml()
+        cxx::negation<detail::has_specialized_from<T>>,     // no toml::from<T>
+        cxx::negation<std::is_constructible<T, const basic_value<TC>&>>
+    >::value, result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    if(v.type() != toml::value_t::array)
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::array));
+    }
+
+    using value_type = typename T::value_type;
+    const auto& a = v.as_array(std::nothrow);
+
+    T container;
+    detail::try_reserve(container, a.size()); // if T has .reserve(), call it
+
+    for(const auto& elem : a)
+    {
+        auto converted = try_get<value_type>(elem);
+        if(converted.is_err())
+        {
+            return err(converted.as_err());
+        }
+        container.push_back(std::move(converted.as_ok()));
+    }
+    return ok(container);
+}
+
+// ============================================================================
+// std::array
+
+template<typename T, typename TC>
+cxx::enable_if_t<detail::is_std_array<T>::value, result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    if(v.type() != toml::value_t::array)
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::array));
+    }
+
+    using value_type = typename T::value_type;
+    const auto& a = v.as_array(std::nothrow);
+
+    T container;
+    if(a.size() != container.size())
+    {
+        const auto loc = v.location();
+        return err(make_error_info("toml::try_get: while converting to an array: "
+            " array size is " + std::to_string(container.size()) +
+            " but there are " + std::to_string(a.size()) + " elements in toml array.",
+            loc, "here"));
+    }
+    for(std::size_t i=0; i<a.size(); ++i)
+    {
+        auto converted = try_get<value_type>(a[i]);
+        if(converted.is_err())
+        {
+            return err(converted.as_err());
+        }
+        container[i] = std::move(converted.as_ok());
+    }
+    return ok(container);
+}
+
+// ============================================================================
+// std::forward_list
+
+template<typename T, typename TC>
+cxx::enable_if_t<detail::is_std_forward_list<T>::value, result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    if(v.type() != toml::value_t::array)
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::array));
+    }
+
+    using value_type = typename T::value_type;
+
+    T container;
+    for(const auto& elem : v.as_array(std::nothrow))
+    {
+        auto converted = try_get<value_type>(elem);
+        if(converted.is_err())
+        {
+            return err(converted.as_err());
+        }
+        container.push_front(std::move(converted.as_ok()));
+    }
+    container.reverse();
+    return ok(container);
+}
+
+// ============================================================================
+// std::pair
+
+template<typename T, typename TC>
+cxx::enable_if_t<detail::is_std_pair<T>::value, result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    if(v.type() != toml::value_t::array)
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::array));
+    }
+
+    using first_type  = typename T::first_type;
+    using second_type = typename T::second_type;
+
+    const auto& ar = v.as_array(std::nothrow);
+    if(ar.size() != 2)
+    {
+        const auto loc = v.location();
+        return err(make_error_info("toml::try_get: while converting std::pair: "
+            " but there are " + std::to_string(ar.size()) +
+            " > 2 elements in toml array.",
+            loc, "here"));
+    }
+
+    auto first_result = try_get<first_type>(ar[0]);
+    if(first_result.is_err())
+    {
+        return err(first_result.as_err());
+    }
+    auto second_result = try_get<second_type>(ar[1]);
+    if(second_result.is_err())
+    {
+        return err(second_result.as_err());
+    }
+    return ok(std::make_pair(std::move(first_result.as_ok()),
+                             std::move(second_result.as_ok())));
+}
+
+// ============================================================================
+// std::tuple.
+
+namespace detail
+{
+template<typename T, std::size_t I, std::size_t N>
+struct try_get_tuple_impl
+{
+    template<typename Array, typename U>
+    static result<T, error_info> invoke(const Array& a, U curr) noexcept
+    {
+        assert(I < a.size());
+        using value_type = typename std::tuple_element<I, T>::type;
+
+        auto converted = try_get<value_type>(a[I]);
+        if(converted.is_err())
+        {
+            return err(converted.as_err());
+        }
+        return try_get_tuple_impl<T, I+1, N>::invoke(a, std::tuple_cat(
+            std::move(curr), std::make_tuple(std::move(converted.as_ok()))));
+    }
+};
+template<typename T, std::size_t I>
+struct try_get_tuple_impl<T, I, I>
+{
+    template<typename Array>
+    static result<T, error_info> invoke(const Array&, T x) noexcept
+    {
+        return ok(std::move(x));
+    }
+};
+} // detail
+
+template<typename T, typename TC>
+cxx::enable_if_t<detail::is_std_tuple<T>::value, result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    if(v.type() != toml::value_t::array)
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::array));
+    }
+
+    const auto& ar = v.as_array(std::nothrow);
+    if(ar.size() != std::tuple_size<T>::value)
+    {
+        const auto loc = v.location();
+        return err(make_error_info("toml::try_get: while converting std::tuple: "
+            " there are " + std::to_string(ar.size()) + " > " +
+            std::to_string(std::tuple_size<T>::value) + " elements in toml array.",
+            loc, "here"));
+    }
+    return detail::try_get_tuple_impl<T, 0, std::tuple_size<T>::value>::invoke(
+            ar, std::make_tuple());
+}
+
+// ============================================================================
+// map-like types; most likely STL map, like std::map or std::unordered_map.
+
+template<typename T, typename TC>
+cxx::enable_if_t<cxx::conjunction<
+        detail::is_map<T>,                                  // T is map
+        detail::is_not_toml_type<T, basic_value<TC>>,       // but not toml::table
+        cxx::negation<detail::has_from_toml_method<T, TC>>, // no T.from_toml()
+        cxx::negation<detail::has_specialized_from<T>>,     // no toml::from<T>
+        cxx::negation<std::is_constructible<T, const basic_value<TC>&>>
+    >::value, result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    using key_type    = typename T::key_type;
+    using mapped_type = typename T::mapped_type;
+    static_assert(
+        std::is_convertible<typename basic_value<TC>::key_type, key_type>::value,
+        "toml::get only supports map type of which key_type is "
+        "convertible from toml::basic_value::key_type.");
+
+    if(v.type() != toml::value_t::table)
+    {
+        return err(detail::make_type_error(v, "try_get()", toml::value_t::table));
+    }
+
+    T m;
+    for(const auto& kv : v.as_table(std::nothrow))
+    {
+        auto converted = try_get<mapped_type>(kv.second);
+        if(converted.is_err())
+        {
+            return err(converted.as_err());
+        }
+        m.emplace(key_type(kv.first), std::move(converted.as_ok()));
+    }
+    return ok(m);
+}
+
+// ============================================================================
+// user-defined type that defines `try_from<T>`.
+
+template<typename T, typename TC>
+cxx::enable_if_t<detail::has_specialized_try_from<T>::value, result<T, error_info>>
+try_get(const basic_value<TC>& v) noexcept
+{
+    return ::toml::try_from<T>::try_from_toml(v);
+}
+
+} // toml
+#endif // TOML11_TRY_GET_HPP

include/toml11/utility.hpp

@@ -99,6 +99,47 @@ inline std::string make_string(std::size_t len, char c)
     return std::string(len, c);
 }
 
+// ---------------------------------------------------------------------------
+
+// It suppresses warnings by -Wsign-conversion when we pass integer literal
+// to toml::find. integer literal `0` is deduced as an int, and will be
+// converted to std::size_t. This causes sign-conversion.
+
+template<typename TC>
+std::size_t key_cast(const std::size_t& v) noexcept
+{
+    return v;
+}
+template<typename TC, typename T>
+cxx::enable_if_t<std::is_integral<cxx::remove_cvref_t<T>>::value, std::size_t>
+key_cast(const T& v) noexcept
+{
+    return static_cast<std::size_t>(v);
+}
+
+// for string-like (string, string literal, string_view)
+
+template<typename TC>
+typename basic_value<TC>::key_type const&
+key_cast(const typename basic_value<TC>::key_type& v) noexcept
+{
+    return v;
+}
+template<typename TC>
+typename basic_value<TC>::key_type
+key_cast(const typename basic_value<TC>::key_type::value_type* v)
+{
+    return typename basic_value<TC>::key_type(v);
+}
+#if defined(TOML11_HAS_STRING_VIEW)
+template<typename TC>
+typename basic_value<TC>::key_type
+key_cast(const std::string_view v)
+{
+    return typename basic_value<TC>::key_type(v);
+}
+#endif // string_view
+
 } // namespace detail
 } // namespace toml
 #endif // TOML11_UTILITY_HPP

include/toml11/value.hpp

@@ -50,6 +50,9 @@ error_info make_type_error(const basic_value<TC>&, const std::string&, const val
 template<typename TC>
 error_info make_not_found_error(const basic_value<TC>&, const std::string&, const std::string&);
 
+template<typename TC>
+error_info make_not_found_error(const basic_value<TC>&, const std::string&, const std::size_t);
+
 template<typename TC>
 void change_region_of_value(basic_value<TC>&, const basic_value<TC>&);
 
@@ -1613,6 +1616,44 @@ class basic_value
         assert(found->first == k);
         return found->second;
     }
+
+    result<std::reference_wrapper<value_type>, error_info>
+    try_at(const key_type& k) noexcept
+    {
+        if(!this->is_table())
+        {
+            return err(detail::make_type_error(*this,
+                        "toml::value::try_at(key_type)", value_t::table));
+        }
+        auto& table = this->as_table(std::nothrow);
+        const auto found = table.find(k);
+        if(found == table.end())
+        {
+            return err(detail::make_not_found_error(*this,
+                        "toml::value::try_at(key_type)", k));
+        }
+        assert(found->first == k);
+        return ok(std::ref(found->second));
+    }
+    result<std::reference_wrapper<const value_type>, error_info>
+    try_at(const key_type& k) const noexcept
+    {
+        if(!this->is_table())
+        {
+            return err(detail::make_type_error(*this,
+                        "toml::value::try_at(key_type)", value_t::table));
+        }
+        const auto& table = this->as_table(std::nothrow);
+        const auto found = table.find(k);
+        if(found == table.end())
+        {
+            return err(detail::make_not_found_error(*this,
+                        "toml::value::try_at(key_type)", k));
+        }
+        assert(found->first == k);
+        return ok(std::cref(found->second));
+    }
+
     value_type& operator[](const key_type& k)
     {
         if(this->is_empty())
@@ -1688,6 +1729,41 @@ class basic_value
         return ar.at(idx);
     }
 
+    result<std::reference_wrapper<value_type>, error_info>
+    try_at(const std::size_t& idx) noexcept
+    {
+        if(!this->is_array())
+        {
+            return err(detail::make_type_error(*this,
+                        "toml::value::try_at(key_type)", value_t::array));
+        }
+        auto& ar = this->as_array(std::nothrow);
+
+        if(ar.size() <= idx)
+        {
+            return err(detail::make_not_found_error(*this,
+                "toml::value::try_at(idx)", idx));
+        }
+        return ok(std::ref(ar[idx]));
+    }
+    result<std::reference_wrapper<const value_type>, error_info>
+    try_at(const std::size_t idx) const noexcept
+    {
+        if(!this->is_array())
+        {
+            return err(detail::make_type_error(*this,
+                        "toml::value::try_at(key_type)", value_t::array));
+        }
+        const auto& ar = this->as_array(std::nothrow);
+
+        if(ar.size() <= idx)
+        {
+            return err(detail::make_not_found_error(*this,
+                "toml::value::try_at(idx)", idx));
+        }
+        return ok(std::cref(ar[idx]));
+    }
+
     value_type&       operator[](const std::size_t idx) noexcept
     {
         // no check...
@@ -2092,6 +2168,19 @@ error_info make_not_found_error(const basic_value<TC>& v, const std::string& fna
     }
     return error_info(title, locs);
 }
+template<typename TC>
+error_info make_not_found_error(const basic_value<TC>& v, const std::string& fname, const std::size_t idx)
+{
+    if( ! v.is_array())
+    {
+        return make_type_error(v, fname, toml::value_t::array);
+    }
+    std::ostringstream oss;
+    oss << "actual length (" << v.as_array(std::nothrow).size()
+        << ") is shorter than the specified index (" << idx << ").";
+    return make_error_info(fname + ": no element corresponding to the index",
+            v, oss.str());
+}
 
 #define TOML11_DETAIL_GENERATE_COMPTIME_GETTER(ty)                              \
     template<typename TC>                                                       \

tests/CMakeLists.txt

@@ -2,11 +2,13 @@ set(TOML11_TEST_NAMES
     test_comments
     test_datetime
     test_find
+    test_try_find
     test_find_or
     test_format_integer
     test_format_floating
     test_format_table
     test_get
+    test_try_get
     test_get_or
     test_location
     test_literal

tests/test_try_find.cpp

@@ -0,0 +1,829 @@
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include "doctest.h"
+
+#include "utility.hpp"
+
+#include <toml11/value.hpp>
+#include <toml11/try_find.hpp>
+
+#include <array>
+#include <deque>
+#include <list>
+#include <map>
+#include <tuple>
+#include <unordered_map>
+
+#if defined(TOML11_HAS_STRING_VIEW)
+#include <string_view>
+#endif
+
+namespace toml
+{
+namespace detail
+{
+std::tm localtime_s(const std::time_t* src);
+std::tm gmtime_s(const std::time_t* src);
+} // detail
+} // toml
+
+TEST_CASE("testing toml::try_find with toml type")
+{
+    using value_type = toml::value;
+    using boolean_type         = typename value_type::boolean_type        ;
+    using integer_type         = typename value_type::integer_type        ;
+    using floating_type        = typename value_type::floating_type       ;
+    using string_type          = typename value_type::string_type         ;
+    using local_time_type      = typename value_type::local_time_type     ;
+    using local_date_type      = typename value_type::local_date_type     ;
+    using local_datetime_type  = typename value_type::local_datetime_type ;
+    using offset_datetime_type = typename value_type::offset_datetime_type;
+    using array_type           = typename value_type::array_type          ;
+    using table_type           = typename value_type::table_type          ;
+
+    {
+        value_type v(toml::table{{"a", true}});
+        CHECK_EQ(true, toml::try_find<boolean_type>(v, "a").unwrap());
+
+        toml::try_find<boolean_type>(v, "a").unwrap() = false;
+        CHECK_EQ(false, toml::try_find<boolean_type>(v, "a").unwrap());
+
+        boolean_type x = toml::try_find<boolean_type>(std::move(v), "a").unwrap();
+        CHECK_EQ(false, x);
+    }
+    {
+        value_type v(toml::table{{"a", 42}});
+        CHECK_EQ(integer_type(42), toml::try_find<integer_type>(v, "a").unwrap());
+
+        toml::try_find<integer_type>(v, "a").unwrap() = 54;
+        CHECK_EQ(integer_type(54), toml::try_find<integer_type>(v, "a").unwrap());
+
+        integer_type x = toml::try_find<integer_type>(std::move(v), "a").unwrap();
+        CHECK_EQ(integer_type(54), x);
+    }
+    {
+        value_type v(toml::table{{"a", 3.14}});
+        CHECK_EQ(floating_type(3.14), toml::try_find<floating_type>(v, "a").unwrap());
+
+        toml::try_find<floating_type>(v, "a").unwrap() = 2.71;
+        CHECK_EQ(floating_type(2.71), toml::try_find<floating_type>(v, "a").unwrap());
+
+        floating_type x = toml::try_find<floating_type>(std::move(v), "a").unwrap();
+        CHECK_EQ(floating_type(2.71), x);
+    }
+    {
+        value_type v(toml::table{{"a", "foo"}});
+        CHECK_EQ("foo", toml::try_find<string_type>(v, "a").unwrap());
+
+        toml::try_find<string_type>(v, "a").unwrap() += "bar";
+        CHECK_EQ("foobar", toml::try_find<string_type>(v, "a").unwrap());
+
+        string_type x = toml::try_find<string_type>(std::move(v), "a").unwrap();
+        CHECK_EQ("foobar", x);
+    }
+    {
+        local_date_type d(2018, toml::month_t::Apr, 22);
+        value_type v(toml::table{{"a", d}});
+        CHECK_EQ(d, toml::try_find<local_date_type>(v, "a").unwrap());
+
+        toml::try_find<local_date_type>(v, "a").unwrap().year = 2017;
+        d.year = 2017;
+        CHECK_EQ(d, toml::try_find<local_date_type>(v, "a").unwrap());
+
+        local_date_type x = toml::try_find<local_date_type>(std::move(v), "a").unwrap();
+        CHECK_EQ(d, x);
+    }
+    {
+        local_time_type t(12, 30, 45);
+        value_type v(toml::table{{"a", t}});
+        CHECK_EQ(t, toml::try_find<local_time_type>(v, "a").unwrap());
+
+        toml::try_find<local_time_type>(v, "a").unwrap().hour = 9;
+        t.hour = 9;
+        CHECK_EQ(t, toml::try_find<local_time_type>(v, "a").unwrap());
+
+        local_time_type x = toml::try_find<local_time_type>(std::move(v), "a").unwrap();
+        CHECK_EQ(t, x);
+    }
+    {
+        local_datetime_type dt(toml::local_date(2018, toml::month_t::Apr, 22),
+                               toml::local_time(12, 30, 45));
+        value_type v(toml::table{{"a", dt}});
+        CHECK_EQ(dt, toml::try_find<local_datetime_type>(v, "a").unwrap());
+
+        toml::try_find<local_datetime_type>(v, "a").unwrap().date.year = 2017;
+        dt.date.year = 2017;
+        CHECK_EQ(dt, toml::try_find<local_datetime_type>(v, "a").unwrap());
+
+        toml::local_datetime x = toml::try_find<local_datetime_type>(std::move(v), "a").unwrap();
+        CHECK_EQ(dt, x);
+    }
+    {
+        offset_datetime_type dt(toml::local_datetime(
+                    toml::local_date(2018, toml::month_t::Apr, 22),
+                    toml::local_time(12, 30, 45)), toml::time_offset(9, 0));
+        value_type v(toml::table{{"a", dt}});
+        CHECK_EQ(dt, toml::try_find<offset_datetime_type>(v, "a").unwrap());
+
+        toml::try_find<toml::offset_datetime>(v, "a").unwrap().date.year = 2017;
+        dt.date.year = 2017;
+        CHECK_EQ(dt, toml::try_find<offset_datetime_type>(v, "a").unwrap());
+
+        offset_datetime_type x = toml::try_find<offset_datetime_type>(std::move(v), "a").unwrap();
+        CHECK_EQ(dt, x);
+    }
+    {
+        array_type vec;
+        vec.push_back(value_type(42));
+        vec.push_back(value_type(54));
+        value_type v(toml::table{{"a", vec}});
+        CHECK_EQ(vec, toml::try_find<array_type>(v, "a").unwrap());
+
+        toml::try_find<array_type>(v, "a").unwrap().push_back(value_type(123));
+        vec.push_back(value_type(123));
+        CHECK_EQ(vec, toml::try_find<array_type>(v, "a").unwrap());
+
+        array_type x = toml::try_find<array_type>(std::move(v), "a").unwrap();
+        CHECK_EQ(vec, x);
+    }
+    {
+        table_type tab;
+        tab["key1"] = value_type(42);
+        tab["key2"] = value_type(3.14);
+        value_type v(toml::table{{"a", tab}});
+        CHECK_EQ(tab, toml::try_find<table_type>(v, "a").unwrap());
+
+        toml::try_find<table_type>(v, "a").unwrap()["key3"] = value_type(123);
+        tab["key3"] = value_type(123);
+        CHECK_EQ(tab, toml::try_find<table_type>(v, "a").unwrap());
+
+        table_type x = toml::try_find<table_type>(std::move(v), "a").unwrap();
+        CHECK_EQ(tab, x);
+    }
+    {
+        value_type v1(toml::table{{"a", 42}});
+        CHECK_EQ(toml::value(42), toml::try_find(v1, "a").unwrap());
+
+        value_type v2(54);
+        toml::try_find(v1, "a").unwrap() = v2;
+        CHECK_EQ(v2, toml::try_find(v1, "a").unwrap());
+
+        value_type x = toml::try_find(std::move(v1), "a").unwrap();
+        CHECK_EQ(v2, x);
+    }
+}
+
+TEST_CASE("testing try_find fails")
+{
+    using value_type = toml::value;
+    using boolean_type         = typename value_type::boolean_type        ;
+    using integer_type         = typename value_type::integer_type        ;
+
+    // -----------------------------------------------------------------------
+    // const-reference version
+    {
+        // value is not a table
+        const toml::value v(true);
+        CHECK_UNARY(toml::try_find<boolean_type>(v, "key").is_err());
+    }
+    {
+        // the value corresponding to the key is not the expected type
+        const toml::value v = toml::table{{"key", 42}};
+        CHECK_UNARY(toml::try_find<boolean_type>(v, "key").is_err());
+    }
+    {
+        // the value corresponding to the key is not found
+        const toml::value v = toml::table{{"key", 42}};
+        CHECK_UNARY(toml::try_find<integer_type>(v, "different_key").is_err());
+    }
+    {
+        // the positive control.
+        const toml::value v = toml::table{{"key", 42}};
+        CHECK_UNARY(toml::try_find<int>(v, "key").is_ok());
+    }
+
+    // -----------------------------------------------------------------------
+    // reference version
+    {
+        // value is not a table
+        toml::value v(true);
+        CHECK_UNARY(toml::try_find<boolean_type>(v, "key").is_err());
+    }
+    {
+        // the value corresponding to the key is not the expected type
+        toml::value v = toml::table{{"key", 42}};
+        CHECK_UNARY(toml::try_find<boolean_type>(v, "key").is_err());
+    }
+    {
+        // the value corresponding to the key is not found
+        toml::value v = toml::table{{"key", 42}};
+        CHECK_UNARY(toml::try_find<integer_type>(v, "different_key").is_err());
+    }
+    {
+        // the positive control.
+        toml::value v = toml::table{{"key", 42}};
+        CHECK_UNARY(toml::try_find<int>(v, "key").is_ok());
+    }
+
+    // -----------------------------------------------------------------------
+    // move version
+
+    {
+        // value is not a table
+        toml::value v(true);
+        CHECK_UNARY(toml::try_find<boolean_type>(std::move(v), "key").is_err());
+    }
+    {
+        // the value corresponding to the key is not the expected type
+        toml::value v = toml::table{{"key", 42}};
+        CHECK_UNARY(toml::try_find<boolean_type>(std::move(v), "key").is_err());
+    }
+    {
+        // the value corresponding to the key is not found
+        toml::value v = toml::table{{"key", 42}};
+        CHECK_UNARY(toml::try_find<integer_type>(std::move(v), "different_key").is_err());
+    }
+    {
+        // the positive control.
+        toml::value v = toml::table{{"key", 42}};
+        CHECK_UNARY(toml::try_find<int>(std::move(v), "key").is_ok());
+    }
+}
+
+TEST_CASE("testing toml::try_find(v, idx) throws")
+{
+    using value_type = toml::value;
+    using boolean_type         = typename value_type::boolean_type        ;
+    using integer_type         = typename value_type::integer_type        ;
+
+    // -----------------------------------------------------------------------
+    // const-reference version
+    {
+        // value is not an array
+        const toml::value v(true);
+        CHECK_UNARY(toml::try_find<boolean_type>(v, 0).is_err());
+    }
+    {
+        // the value corresponding to the key is not the expected type
+        const toml::value v = toml::array{1, 2, 3, 4, 5};
+        CHECK_UNARY(toml::try_find<boolean_type>(v, 0).is_err());
+    }
+    {
+        // the value corresponding to the key is not found
+        const toml::value v = toml::array{1, 2, 3, 4, 5};
+        CHECK_UNARY(toml::try_find<integer_type>(v, 6).is_err());
+    }
+    {
+        // the positive control.
+        const toml::value v = toml::array{1, 2, 3, 4, 5};
+        CHECK_UNARY(toml::try_find<int>(v, 2).is_ok());
+    }
+
+    // -----------------------------------------------------------------------
+    // non-const reference version
+    {
+        // value is not an array
+        toml::value v(true);
+        CHECK_UNARY(toml::try_find<boolean_type>(v, 0).is_err());
+    }
+    {
+        // the value corresponding to the key is not the expected type
+        toml::value v = toml::array{1, 2, 3, 4, 5};
+        CHECK_UNARY(toml::try_find<boolean_type>(v, 0).is_err());
+    }
+    {
+        // the value corresponding to the key is not found
+        toml::value v = toml::array{1, 2, 3, 4, 5};
+        CHECK_UNARY(toml::try_find<integer_type>(v, 6).is_err());
+    }
+    {
+        // the positive control.
+        toml::value v = toml::array{1, 2, 3, 4, 5};
+        CHECK_UNARY(toml::try_find<int>(v, 2).is_ok());
+    }
+
+    // -----------------------------------------------------------------------
+    // move version
+    {
+        // value is not an array
+        toml::value v(true);
+        CHECK_UNARY(toml::try_find<boolean_type>(std::move(v), 0).is_err());
+    }
+    {
+        // the value corresponding to the key is not the expected type
+        toml::value v = toml::array{1, 2, 3, 4, 5};
+        CHECK_UNARY(toml::try_find<boolean_type>(std::move(v), 0).is_err());
+    }
+    {
+        // the value corresponding to the key is not found
+        toml::value v = toml::array{1, 2, 3, 4, 5};
+        CHECK_UNARY(toml::try_find<integer_type>(std::move(v), 6).is_err());
+    }
+    {
+        // the positive control.
+        toml::value v = toml::array{1, 2, 3, 4, 5};
+        CHECK_UNARY(toml::try_find<int>(std::move(v), 2).is_ok());
+    }
+}
+
+TEST_CASE("testing toml::try_find with recursive table/array")
+{
+    using value_type = toml::value;
+    using integer_type         = typename value_type::integer_type        ;
+
+    // recursively search tables
+    {
+        toml::value v = toml::table{
+            {"a", toml::table{
+                {"b", toml::table{
+                    {"c", toml::table{
+                        {"d", 42}
+                    }}
+                }}
+            }}
+        };
+        CHECK_EQ(42, toml::try_find<int>(v, "a", "b", "c", "d").unwrap());
+
+        // reference that can be used to modify the content
+        auto num = toml::try_find<integer_type>(v, "a", "b", "c", "d");
+        CHECK_UNARY(num.is_ok());
+        num.unwrap() = 54;
+        CHECK_EQ(54, toml::try_find<int>(v, "a", "b", "c", "d").unwrap());
+
+        const std::string a("a"), b("b"), c("c"), d("d");
+        auto num2 = toml::try_find<integer_type>(v, a, b, c, d);
+        CHECK_UNARY(num2.is_ok());
+        num2.unwrap() = 42;
+        CHECK_EQ(42, toml::try_find<int>(v, a, b, c, d).unwrap());
+
+        auto num3 = toml::try_find<integer_type>(v, a, "b", c, "d");
+        CHECK_EQ(42, num3.unwrap());
+
+        auto num4 = toml::try_find<integer_type>(std::move(v), a, b, c, d);
+        CHECK_EQ(42, num4.unwrap());
+    }
+    // recursively search arrays
+    {
+        toml::value v = toml::array{
+            toml::array{"array", "of", "string"},
+            toml::array{toml::array{1, 2, 3}, toml::array{3.14, 2.71}}
+        };
+        CHECK_EQ("array" , toml::try_find<std::string>(v, 0, 0).unwrap());
+        CHECK_EQ("of"    , toml::try_find<std::string>(v, 0, 1).unwrap());
+        CHECK_EQ("string", toml::try_find<std::string>(v, 0, 2).unwrap());
+
+        CHECK_EQ(1, toml::try_find<int>(v, 1, 0, 0).unwrap());
+        CHECK_EQ(2, toml::try_find<int>(v, 1, 0, 1).unwrap());
+        CHECK_EQ(3, toml::try_find<int>(v, 1, 0, 2).unwrap());
+
+        CHECK_EQ(3.14, toml::try_find<double>(v, 1, 1, 0).unwrap());
+        CHECK_EQ(2.71, toml::try_find<double>(v, 1, 1, 1).unwrap());
+
+        // reference that can be used to modify the content
+        auto num = toml::try_find<integer_type>(v, 1, 0, 2);
+        num.unwrap() = 42;
+        CHECK_EQ( 1, toml::try_find<int>(v, 1, 0, 0).unwrap());
+        CHECK_EQ( 2, toml::try_find<int>(v, 1, 0, 1).unwrap());
+        CHECK_EQ(42, toml::try_find<int>(v, 1, 0, 2).unwrap());
+
+        // move value
+        auto num2 = toml::try_find<integer_type>(std::move(v), 1, 0, 2);
+        CHECK_EQ(42, num2.unwrap());
+    }
+    // recursively search mixtures
+    {
+        toml::value v = toml::table{{"array", toml::array{
+                toml::array{1,   2,   3},
+                toml::array{
+                    toml::table{{"foo", "bar"}, {"baz", "qux"}},
+                    toml::table{{"pi",   3.14}, {"e",    2.71}}
+                }}
+            }};
+
+        CHECK_EQ(1, toml::try_find<int>(v, "array", 0, 0).unwrap());
+        CHECK_EQ(2, toml::try_find<int>(v, "array", 0, 1).unwrap());
+        CHECK_EQ(3, toml::try_find<int>(v, "array", 0, 2).unwrap());
+
+        CHECK_EQ("bar", toml::try_find<std::string>(v, "array", 1, 0, "foo").unwrap());
+        CHECK_EQ("qux", toml::try_find<std::string>(v, "array", 1, 0, "baz").unwrap());
+
+        CHECK_EQ(3.14, toml::try_find<double>(v, "array", 1, 1, "pi").unwrap());
+        CHECK_EQ(2.71, toml::try_find<double>(v, "array", 1, 1, "e" ).unwrap());
+
+        const std::string ar("array");
+        const auto ar_c = "array";
+
+        const std::string pi("pi");
+        const auto pi_c = "pi";
+
+        CHECK_EQ(3.14, toml::try_find<double>(v, ar, 1, 1, "pi").unwrap());
+        CHECK_EQ(3.14, toml::try_find<double>(v, ar, 1, 1, pi)  .unwrap());
+        CHECK_EQ(3.14, toml::try_find<double>(v, ar, 1, 1, pi_c).unwrap());
+
+        CHECK_EQ(3.14, toml::try_find<double>(v, ar_c, 1, 1, "pi").unwrap());
+        CHECK_EQ(3.14, toml::try_find<double>(v, ar_c, 1, 1, pi)  .unwrap());
+        CHECK_EQ(3.14, toml::try_find<double>(v, ar_c, 1, 1, pi_c).unwrap());
+
+        CHECK_EQ(3.14, toml::try_find<double>(v, "array", 1, 1, pi)  .unwrap());
+        CHECK_EQ(3.14, toml::try_find<double>(v, "array", 1, 1, pi_c).unwrap());
+    }
+}
+
+TEST_CASE("testing toml::try_find integer conversion")
+{
+    using value_type = toml::value;
+
+    {
+        value_type v = toml::table{{"key", 42}};
+        CHECK_EQ(int(42)          , toml::try_find<int          >(v, "key").unwrap());
+        CHECK_EQ(short(42)        , toml::try_find<short        >(v, "key").unwrap());
+        CHECK_EQ(char(42)         , toml::try_find<char         >(v, "key").unwrap());
+        CHECK_EQ(unsigned(42)     , toml::try_find<unsigned     >(v, "key").unwrap());
+        CHECK_EQ(long(42)         , toml::try_find<long         >(v, "key").unwrap());
+        CHECK_EQ(std::int64_t(42) , toml::try_find<std::int64_t >(v, "key").unwrap());
+        CHECK_EQ(std::uint64_t(42), toml::try_find<std::uint64_t>(v, "key").unwrap());
+        CHECK_EQ(std::int16_t(42) , toml::try_find<std::int16_t >(v, "key").unwrap());
+        CHECK_EQ(std::uint16_t(42), toml::try_find<std::uint16_t>(v, "key").unwrap());
+        CHECK_EQ(std::uint16_t(42), toml::try_find<std::uint16_t>(std::move(v), "key").unwrap());
+    }
+}
+
+TEST_CASE("testing toml::try_find floating conversion")
+{
+    using value_type = toml::value;
+
+    {
+        value_type v = toml::table{{"key", 3.14}};
+        const double ref(3.14);
+        CHECK_EQ(static_cast<float      >(ref), toml::try_find<float      >(v, "key").unwrap());
+        CHECK_EQ(                         ref , toml::try_find<double     >(v, "key").unwrap());
+        CHECK_EQ(static_cast<long double>(ref), toml::try_find<long double>(v, "key").unwrap());
+        CHECK_EQ(static_cast<float      >(ref), toml::try_find<float      >(std::move(v), "key").unwrap());
+    }
+}
+
+TEST_CASE("testing toml::try_find string conversion")
+{
+    using value_type = toml::value;
+
+    {
+        value_type v = toml::table{{"key", "foo"}};
+        CHECK_EQ("foo", toml::try_find<std::string>(v, "key").unwrap());
+        toml::try_find<std::string>(v, "key").unwrap() += "bar";
+        CHECK_EQ("foobar", toml::try_find<std::string>(v, "key").unwrap());
+    }
+
+#if TOML11_CPLUSPLUS_STANDARD_VERSION >= 201703L
+    {
+        value_type v = toml::table{{"key", "foo"}};
+        CHECK_EQ("foo", toml::try_find<std::string_view>(v, "key").unwrap());
+    }
+#endif
+}
+
+TEST_CASE("testing toml::try_find array conversion")
+{
+    using value_type = toml::value;
+
+    value_type v = toml::table{{"key", toml::array{42, 54, 69, 72}}};
+
+    const std::vector<int>         vec = toml::try_find<std::vector<int>>(v, "key").unwrap();
+    const std::list<short>         lst = toml::try_find<std::list<short>>(v, "key").unwrap();
+    const std::deque<std::int64_t> deq = toml::try_find<std::deque<std::int64_t>>(v, "key").unwrap();
+
+    CHECK_EQ(42, vec.at(0));
+    CHECK_EQ(54, vec.at(1));
+    CHECK_EQ(69, vec.at(2));
+    CHECK_EQ(72, vec.at(3));
+
+    std::list<short>::const_iterator iter = lst.begin();
+    CHECK_EQ(static_cast<short>(42), *(iter++));
+    CHECK_EQ(static_cast<short>(54), *(iter++));
+    CHECK_EQ(static_cast<short>(69), *(iter++));
+    CHECK_EQ(static_cast<short>(72), *(iter++));
+
+    CHECK_EQ(static_cast<std::int64_t>(42), deq.at(0));
+    CHECK_EQ(static_cast<std::int64_t>(54), deq.at(1));
+    CHECK_EQ(static_cast<std::int64_t>(69), deq.at(2));
+    CHECK_EQ(static_cast<std::int64_t>(72), deq.at(3));
+
+    std::array<int, 4> ary = toml::try_find<std::array<int, 4>>(v, "key").unwrap();
+    CHECK_EQ(42, ary.at(0));
+    CHECK_EQ(54, ary.at(1));
+    CHECK_EQ(69, ary.at(2));
+    CHECK_EQ(72, ary.at(3));
+
+    std::tuple<int, short, unsigned, long> tpl =
+        toml::try_find<std::tuple<int, short, unsigned, long>>(v, "key").unwrap();
+    CHECK_EQ(                      42 , std::get<0>(tpl));
+    CHECK_EQ(static_cast<short   >(54), std::get<1>(tpl));
+    CHECK_EQ(static_cast<unsigned>(69), std::get<2>(tpl));
+    CHECK_EQ(static_cast<long    >(72), std::get<3>(tpl));
+
+    value_type p = toml::table{{"key", toml::array{3.14, 2.71}}};
+    std::pair<double, double> pr = toml::try_find<std::pair<double, double> >(p, "key").unwrap();
+    CHECK_EQ(3.14, pr.first);
+    CHECK_EQ(2.71, pr.second);
+}
+
+TEST_CASE("testing toml::try_find array move conversion")
+{
+    using value_type = toml::value;
+
+    value_type v1 = toml::table{{"key", toml::array{42, 54, 69, 72}}};
+    value_type v2 = toml::table{{"key", toml::array{42, 54, 69, 72}}};
+    value_type v3 = toml::table{{"key", toml::array{42, 54, 69, 72}}};
+    value_type v4 = toml::table{{"key", toml::array{42, 54, 69, 72}}};
+    value_type v5 = toml::table{{"key", toml::array{42, 54, 69, 72}}};
+
+    const std::vector<int>         vec = toml::try_find<std::vector<int>>(std::move(v1), "key").unwrap();
+    const std::list<short>         lst = toml::try_find<std::list<short>>(std::move(v2), "key").unwrap();
+    const std::deque<std::int64_t> deq = toml::try_find<std::deque<std::int64_t>>(std::move(v3), "key").unwrap();
+
+    CHECK_EQ(42, vec.at(0));
+    CHECK_EQ(54, vec.at(1));
+    CHECK_EQ(69, vec.at(2));
+    CHECK_EQ(72, vec.at(3));
+
+    std::list<short>::const_iterator iter = lst.begin();
+    CHECK_EQ(static_cast<short>(42), *(iter++));
+    CHECK_EQ(static_cast<short>(54), *(iter++));
+    CHECK_EQ(static_cast<short>(69), *(iter++));
+    CHECK_EQ(static_cast<short>(72), *(iter++));
+
+    CHECK_EQ(static_cast<std::int64_t>(42), deq.at(0));
+    CHECK_EQ(static_cast<std::int64_t>(54), deq.at(1));
+    CHECK_EQ(static_cast<std::int64_t>(69), deq.at(2));
+    CHECK_EQ(static_cast<std::int64_t>(72), deq.at(3));
+
+    std::array<int, 4> ary = toml::try_find<std::array<int, 4>>(std::move(v4), "key").unwrap();
+    CHECK_EQ(42, ary.at(0));
+    CHECK_EQ(54, ary.at(1));
+    CHECK_EQ(69, ary.at(2));
+    CHECK_EQ(72, ary.at(3));
+
+    std::tuple<int, short, unsigned, long> tpl =
+        toml::try_find<std::tuple<int, short, unsigned, long>>(std::move(v5), "key").unwrap();
+    CHECK_EQ(                      42 , std::get<0>(tpl));
+    CHECK_EQ(static_cast<short   >(54), std::get<1>(tpl));
+    CHECK_EQ(static_cast<unsigned>(69), std::get<2>(tpl));
+    CHECK_EQ(static_cast<long    >(72), std::get<3>(tpl));
+
+    value_type p = toml::table{{"key", toml::array{3.14, 2.71}}};
+    std::pair<double, double> pr = toml::try_find<std::pair<double, double> >(std::move(p), "key").unwrap();
+    CHECK_EQ(3.14, pr.first);
+    CHECK_EQ(2.71, pr.second);
+}
+
+TEST_CASE("testing toml::try_find array of array conversion")
+{
+    using value_type = toml::value;
+
+    value_type v1 = toml::array{42, 54, 69, 72};
+    value_type v2 = toml::array{"foo", "bar", "baz"};
+    value_type v = toml::table{{"key", toml::array{v1, v2}}};
+
+    std::pair<std::vector<int>, std::vector<std::string>> p =
+        toml::try_find<std::pair<std::vector<int>, std::vector<std::string>>>(v, "key").unwrap();
+
+    CHECK_EQ(p.first.at(0), 42);
+    CHECK_EQ(p.first.at(1), 54);
+    CHECK_EQ(p.first.at(2), 69);
+    CHECK_EQ(p.first.at(3), 72);
+
+    CHECK_EQ(p.second.at(0), "foo");
+    CHECK_EQ(p.second.at(1), "bar");
+    CHECK_EQ(p.second.at(2), "baz");
+
+    std::tuple<std::vector<int>, std::vector<std::string>> t =
+        toml::try_find<std::tuple<std::vector<int>, std::vector<std::string>>>(v, "key").unwrap();
+
+    CHECK_EQ(std::get<0>(t).at(0), 42);
+    CHECK_EQ(std::get<0>(t).at(1), 54);
+    CHECK_EQ(std::get<0>(t).at(2), 69);
+    CHECK_EQ(std::get<0>(t).at(3), 72);
+
+    CHECK_EQ(std::get<1>(t).at(0), "foo");
+    CHECK_EQ(std::get<1>(t).at(1), "bar");
+    CHECK_EQ(std::get<1>(t).at(2), "baz");
+}
+
+TEST_CASE("testing toml::try_find array of array move conversion")
+{
+    using value_type = toml::value;
+
+    value_type a1 = toml::array{42, 54, 69, 72};
+    value_type a2 = toml::array{"foo", "bar", "baz"};
+    value_type v1 = toml::table{{"key", toml::array{a1, a2}}};
+    value_type v2 = toml::table{{"key", toml::array{a1, a2}}};
+
+    std::pair<std::vector<int>, std::vector<std::string>> p =
+        toml::try_find<std::pair<std::vector<int>, std::vector<std::string>>>(std::move(v1), "key").unwrap();
+
+    CHECK_EQ(p.first.at(0), 42);
+    CHECK_EQ(p.first.at(1), 54);
+    CHECK_EQ(p.first.at(2), 69);
+    CHECK_EQ(p.first.at(3), 72);
+
+    CHECK_EQ(p.second.at(0), "foo");
+    CHECK_EQ(p.second.at(1), "bar");
+    CHECK_EQ(p.second.at(2), "baz");
+
+    std::tuple<std::vector<int>, std::vector<std::string>> t =
+        toml::try_find<std::tuple<std::vector<int>, std::vector<std::string>>>(std::move(v2), "key").unwrap();
+
+    CHECK_EQ(std::get<0>(t).at(0), 42);
+    CHECK_EQ(std::get<0>(t).at(1), 54);
+    CHECK_EQ(std::get<0>(t).at(2), 69);
+    CHECK_EQ(std::get<0>(t).at(3), 72);
+
+    CHECK_EQ(std::get<1>(t).at(0), "foo");
+    CHECK_EQ(std::get<1>(t).at(1), "bar");
+    CHECK_EQ(std::get<1>(t).at(2), "baz");
+}
+
+TEST_CASE("testing toml::try_find table conversion")
+{
+    using value_type = toml::value;
+    {
+        value_type v1 = toml::table{{"key", toml::table{
+                {"key1", 1}, {"key2", 2}, {"key3", 3}, {"key4", 4}
+            }}};
+        const auto v = toml::try_find<std::map<std::string, int>>(v1, "key").unwrap();
+        CHECK_EQ(v.at("key1"), 1);
+        CHECK_EQ(v.at("key2"), 2);
+        CHECK_EQ(v.at("key3"), 3);
+        CHECK_EQ(v.at("key4"), 4);
+    }
+    {
+        value_type v1 = toml::table{{"key", toml::table{
+                {"key1", 1}, {"key2", 2}, {"key3", 3}, {"key4", 4}
+            }}};
+        const auto v = toml::try_find<std::map<std::string, int>>(std::move(v1), "key").unwrap();
+        CHECK_EQ(v.at("key1"), 1);
+        CHECK_EQ(v.at("key2"), 2);
+        CHECK_EQ(v.at("key3"), 3);
+        CHECK_EQ(v.at("key4"), 4);
+    }
+}
+
+TEST_CASE("testing toml::try_find local_date")
+{
+    using value_type = toml::value;
+    {
+        value_type v1 = toml::table{{"key", toml::local_date{2018, toml::month_t::Apr, 1}}};
+        const auto date = std::chrono::system_clock::to_time_t(
+                toml::try_find<std::chrono::system_clock::time_point>(v1, "key").unwrap());
+
+        std::tm t;
+        t.tm_year = 2018 - 1900;
+        t.tm_mon  = 4    - 1;
+        t.tm_mday = 1;
+        t.tm_hour = 0;
+        t.tm_min  = 0;
+        t.tm_sec  = 0;
+        t.tm_isdst = -1;
+        const auto c = std::mktime(&t);
+        CHECK_EQ(c, date);
+    }
+    {
+        value_type v1 = toml::table{{"key", toml::local_date{2018, toml::month_t::Apr, 1}}};
+        const auto date = std::chrono::system_clock::to_time_t(
+                toml::try_find<std::chrono::system_clock::time_point>(std::move(v1), "key").unwrap());
+
+        std::tm t;
+        t.tm_year = 2018 - 1900;
+        t.tm_mon  = 4    - 1;
+        t.tm_mday = 1;
+        t.tm_hour = 0;
+        t.tm_min  = 0;
+        t.tm_sec  = 0;
+        t.tm_isdst = -1;
+        const auto c = std::mktime(&t);
+        CHECK_EQ(c, date);
+    }
+}
+
+TEST_CASE("testing toml::try_find local_time")
+{
+    using value_type = toml::value;
+    {
+        value_type v1 = toml::table{{"key", toml::local_time{12, 30, 45}}};
+        const auto time = toml::try_find<std::chrono::seconds>(v1, "key").unwrap();
+        CHECK_EQ(time, std::chrono::hours(12) +
+                            std::chrono::minutes(30) + std::chrono::seconds(45));
+    }
+    {
+        value_type v1 = toml::table{{"key", toml::local_time{12, 30, 45}}};
+        const auto time = toml::try_find<std::chrono::seconds>(std::move(v1), "key").unwrap();
+        CHECK_EQ(time, std::chrono::hours(12) +
+                            std::chrono::minutes(30) + std::chrono::seconds(45));
+    }
+}
+
+TEST_CASE("testing toml::try_find local_datetime")
+{
+    using value_type = toml::value;
+    {
+        value_type v1 = toml::table{{"key", toml::local_datetime(
+                    toml::local_date{2018, toml::month_t::Apr, 1},
+                    toml::local_time{12, 30, 45})}};
+
+        const auto date = std::chrono::system_clock::to_time_t(
+                toml::try_find<std::chrono::system_clock::time_point>(v1, "key").unwrap());
+        std::tm t;
+        t.tm_year = 2018 - 1900;
+        t.tm_mon  = 4    - 1;
+        t.tm_mday = 1;
+        t.tm_hour = 12;
+        t.tm_min  = 30;
+        t.tm_sec  = 45;
+        t.tm_isdst = -1;
+        const auto c = std::mktime(&t);
+        CHECK_EQ(c,  date);
+    }
+    {
+        value_type v1 = toml::table{{"key", toml::local_datetime(
+                    toml::local_date{2018, toml::month_t::Apr, 1},
+                    toml::local_time{12, 30, 45})}};
+
+        const auto date = std::chrono::system_clock::to_time_t(
+                toml::try_find<std::chrono::system_clock::time_point>(std::move(v1), "key").unwrap());
+        std::tm t;
+        t.tm_year = 2018 - 1900;
+        t.tm_mon  = 4    - 1;
+        t.tm_mday = 1;
+        t.tm_hour = 12;
+        t.tm_min  = 30;
+        t.tm_sec  = 45;
+        t.tm_isdst = -1;
+        const auto c = std::mktime(&t);
+        CHECK_EQ(c,  date);
+    }
+}
+
+TEST_CASE("testing toml::try_find offset_datetime")
+{
+    using value_type = toml::value;
+    {
+        value_type v1 = toml::table{{"key", toml::offset_datetime(
+                    toml::local_date{2018, toml::month_t::Apr, 1},
+                    toml::local_time{12, 30, 0},
+                    toml::time_offset{9, 0})}};
+        //    2018-04-01T12:30:00+09:00
+        //,  2018-04-01T03:30:00Z
+
+        const auto date = toml::try_find<std::chrono::system_clock::time_point>(v1, "key").unwrap();
+        const auto timet = std::chrono::system_clock::to_time_t(date);
+
+        // get time_t as gmtime (2018-04-01T03:30:00Z)
+        const auto tm = toml::detail::gmtime_s(std::addressof(timet));
+        CHECK_EQ(tm.tm_year + 1900,  2018);
+        CHECK_EQ(tm.tm_mon  + 1,        4);
+        CHECK_EQ(tm.tm_mday,            1);
+        CHECK_EQ(tm.tm_hour,            3);
+        CHECK_EQ(tm.tm_min,            30);
+        CHECK_EQ(tm.tm_sec,             0);
+    }
+
+    {
+        value_type v1 = toml::table{{"key", toml::offset_datetime(
+                    toml::local_date{2018, toml::month_t::Apr, 1},
+                    toml::local_time{12, 30, 0},
+                    toml::time_offset{-8, 0})}};
+        //    2018-04-01T12:30:00-08:00
+        //,  2018-04-01T20:30:00Z
+
+        const auto date = toml::try_find<std::chrono::system_clock::time_point>(v1, "key").unwrap();
+        const auto timet = std::chrono::system_clock::to_time_t(date);
+
+        // get time_t as gmtime (2018-04-01T03:30:00Z)
+        const auto tm = toml::detail::gmtime_s(std::addressof(timet));
+        CHECK_EQ(tm.tm_year + 1900,  2018);
+        CHECK_EQ(tm.tm_mon  + 1,        4);
+        CHECK_EQ(tm.tm_mday,            1);
+        CHECK_EQ(tm.tm_hour,           20);
+        CHECK_EQ(tm.tm_min,            30);
+        CHECK_EQ(tm.tm_sec,             0);
+    }
+
+    {
+        value_type v1 = toml::table{{"key", toml::offset_datetime(
+                    toml::local_date{2018, toml::month_t::Apr, 1},
+                    toml::local_time{12, 30, 0},
+                    toml::time_offset{-8, 0})}};
+        //    2018-04-01T12:30:00-08:00
+        //,  2018-04-01T20:30:00Z
+
+        const auto date = toml::try_find<std::chrono::system_clock::time_point>(std::move(v1), "key").unwrap();
+        const auto timet = std::chrono::system_clock::to_time_t(date);
+
+        // get time_t as gmtime (2018-04-01T03:30:00Z)
+        const auto tm = toml::detail::gmtime_s(std::addressof(timet));
+        CHECK_EQ(tm.tm_year + 1900,  2018);
+        CHECK_EQ(tm.tm_mon  + 1,        4);
+        CHECK_EQ(tm.tm_mday,            1);
+        CHECK_EQ(tm.tm_hour,           20);
+        CHECK_EQ(tm.tm_min,            30);
+        CHECK_EQ(tm.tm_sec,             0);
+    }
+}

tests/test_try_get.cpp

@@ -0,0 +1,529 @@
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include "doctest.h"
+
+#include "utility.hpp"
+
+#include <toml11/value.hpp>
+#include <toml11/try_get.hpp>
+
+#include <array>
+#include <deque>
+#include <list>
+#include <map>
+#include <tuple>
+#include <unordered_map>
+
+#if TOML11_CPLUSPLUS_STANDARD_VERSION >= 201703L
+#include <string_view>
+#endif
+
+namespace toml
+{
+namespace detail
+{
+std::tm localtime_s(const std::time_t* src);
+std::tm gmtime_s(const std::time_t* src);
+} // detail
+} // toml
+
+TEST_CASE("testing toml::try_get with toml types")
+{
+    using value_type = toml::value;
+    using boolean_type         = typename value_type::boolean_type        ;
+    using integer_type         = typename value_type::integer_type        ;
+    using floating_type        = typename value_type::floating_type       ;
+    using string_type          = typename value_type::string_type         ;
+    using local_time_type      = typename value_type::local_time_type     ;
+    using local_date_type      = typename value_type::local_date_type     ;
+    using local_datetime_type  = typename value_type::local_datetime_type ;
+    using offset_datetime_type = typename value_type::offset_datetime_type;
+    using array_type           = typename value_type::array_type          ;
+    using table_type           = typename value_type::table_type          ;
+
+    {
+        value_type v(true);
+        CHECK_EQ(true, toml::try_get<boolean_type>(v).unwrap());
+
+        toml::try_get<boolean_type>(v).unwrap() = false;
+        CHECK_EQ(false, toml::try_get<boolean_type>(v).unwrap());
+
+        boolean_type x = toml::try_get<boolean_type>(std::move(v)).unwrap();
+        CHECK_EQ(false, x);
+    }
+    {
+        value_type v(42);
+        CHECK_EQ(integer_type(42), toml::try_get<integer_type>(v).unwrap());
+
+        toml::try_get<integer_type>(v).unwrap() = 54;
+        CHECK_EQ(integer_type(54), toml::try_get<integer_type>(v).unwrap());
+
+        integer_type x = toml::try_get<integer_type>(std::move(v)).unwrap();
+        CHECK_EQ(integer_type(54), x);
+    }
+    {
+        value_type v(3.14);
+        CHECK_EQ(floating_type(3.14), toml::try_get<floating_type>(v).unwrap());
+
+        toml::try_get<floating_type>(v).unwrap() = 2.71;
+        CHECK_EQ(floating_type(2.71), toml::try_get<floating_type>(v).unwrap());
+
+        floating_type x = toml::try_get<floating_type>(std::move(v)).unwrap();
+        CHECK_EQ(floating_type(2.71), x);
+    }
+    {
+        value_type v("foo");
+        CHECK_EQ("foo", toml::try_get<string_type>(v).unwrap());
+
+        toml::try_get<string_type>(v).unwrap() += "bar";
+        CHECK_EQ("foobar", toml::try_get<string_type>(v).unwrap());
+
+        string_type x = toml::try_get<string_type>(std::move(v)).unwrap();
+        CHECK_EQ("foobar", x);
+    }
+    {
+        local_date_type d(2018, toml::month_t::Apr, 22);
+        value_type v(d);
+        CHECK_EQ(d, toml::try_get<local_date_type>(v).unwrap());
+
+        toml::try_get<local_date_type>(v).unwrap().year = 2017;
+        d.year = 2017;
+        CHECK_EQ(d, toml::try_get<local_date_type>(v).unwrap());
+
+        local_date_type x = toml::try_get<local_date_type>(std::move(v)).unwrap();
+        CHECK_EQ(d, x);
+    }
+    {
+        local_time_type t(12, 30, 45);
+        value_type v(t);
+        CHECK_EQ(t, toml::try_get<local_time_type>(v).unwrap());
+
+        toml::try_get<local_time_type>(v).unwrap().hour = 9;
+        t.hour = 9;
+        CHECK_EQ(t, toml::try_get<local_time_type>(v).unwrap());
+
+        local_time_type x = toml::try_get<local_time_type>(std::move(v)).unwrap();
+        CHECK_EQ(t, x);
+    }
+    {
+        local_datetime_type dt(toml::local_date(2018, toml::month_t::Apr, 22),
+                               toml::local_time(12, 30, 45));
+        value_type v(dt);
+        CHECK_EQ(dt, toml::try_get<local_datetime_type>(v).unwrap());
+
+        toml::try_get<local_datetime_type>(v).unwrap().date.year = 2017;
+        dt.date.year = 2017;
+        CHECK_EQ(dt, toml::try_get<local_datetime_type>(v).unwrap());
+
+        toml::local_datetime x = toml::try_get<local_datetime_type>(std::move(v)).unwrap();
+        CHECK_EQ(dt, x);
+    }
+    {
+        offset_datetime_type dt(toml::local_datetime(
+                    toml::local_date(2018, toml::month_t::Apr, 22),
+                    toml::local_time(12, 30, 45)), toml::time_offset(9, 0));
+        value_type v(dt);
+        CHECK_EQ(dt, toml::try_get<offset_datetime_type>(v).unwrap());
+
+        toml::try_get<toml::offset_datetime>(v).unwrap().date.year = 2017;
+        dt.date.year = 2017;
+        CHECK_EQ(dt, toml::try_get<offset_datetime_type>(v).unwrap());
+
+        offset_datetime_type x = toml::try_get<offset_datetime_type>(std::move(v)).unwrap();
+        CHECK_EQ(dt, x);
+    }
+    {
+        array_type vec;
+        vec.push_back(value_type(42));
+        vec.push_back(value_type(54));
+        value_type v(vec);
+        CHECK_EQ(vec, toml::try_get<array_type>(v).unwrap());
+
+        toml::try_get<array_type>(v).unwrap().push_back(value_type(123));
+        vec.push_back(value_type(123));
+        CHECK_EQ(vec, toml::try_get<array_type>(v).unwrap());
+
+        array_type x = toml::try_get<array_type>(std::move(v)).unwrap();
+        CHECK_EQ(vec, x);
+    }
+    {
+        table_type tab;
+        tab["key1"] = value_type(42);
+        tab["key2"] = value_type(3.14);
+        value_type v(tab);
+        CHECK_EQ(tab, toml::try_get<table_type>(v).unwrap());
+
+        toml::try_get<table_type>(v).unwrap()["key3"] = value_type(123);
+        tab["key3"] = value_type(123);
+        CHECK_EQ(tab, toml::try_get<table_type>(v).unwrap());
+
+        table_type x = toml::try_get<table_type>(std::move(v)).unwrap();
+        CHECK_EQ(tab, x);
+    }
+    {
+        value_type v1(42);
+        CHECK_EQ(v1, toml::try_get<value_type>(v1).unwrap());
+
+        value_type v2(54);
+        toml::try_get<value_type>(v1).unwrap() = v2;
+        CHECK_EQ(v2, toml::try_get<value_type>(v1).unwrap());
+
+        value_type x = toml::try_get<value_type>(std::move(v1)).unwrap();
+        CHECK_EQ(v2, x);
+    }
+}
+
+TEST_CASE("testing toml::try_get<integer-like>")
+{
+    using value_type = toml::value;
+    {
+        value_type v(42);
+
+        CHECK_EQ(int(42),           toml::try_get<int          >(v).unwrap());
+        CHECK_EQ(short(42),         toml::try_get<short        >(v).unwrap());
+        CHECK_EQ(char(42),          toml::try_get<char         >(v).unwrap());
+        CHECK_EQ(unsigned(42),      toml::try_get<unsigned     >(v).unwrap());
+        CHECK_EQ(long(42),          toml::try_get<long         >(v).unwrap());
+        CHECK_EQ(std::int64_t(42),  toml::try_get<std::int64_t >(v).unwrap());
+        CHECK_EQ(std::uint64_t(42), toml::try_get<std::uint64_t>(v).unwrap());
+        CHECK_EQ(std::int16_t(42),  toml::try_get<std::int16_t >(v).unwrap());
+        CHECK_EQ(std::uint16_t(42), toml::try_get<std::uint16_t>(v).unwrap());
+
+        CHECK_EQ(int(42),           toml::try_get<int          >(as_const(v)).unwrap());
+        CHECK_EQ(short(42),         toml::try_get<short        >(as_const(v)).unwrap());
+        CHECK_EQ(char(42),          toml::try_get<char         >(as_const(v)).unwrap());
+        CHECK_EQ(unsigned(42),      toml::try_get<unsigned     >(as_const(v)).unwrap());
+        CHECK_EQ(long(42),          toml::try_get<long         >(as_const(v)).unwrap());
+        CHECK_EQ(std::int64_t(42),  toml::try_get<std::int64_t >(as_const(v)).unwrap());
+        CHECK_EQ(std::uint64_t(42), toml::try_get<std::uint64_t>(as_const(v)).unwrap());
+        CHECK_EQ(std::int16_t(42),  toml::try_get<std::int16_t >(as_const(v)).unwrap());
+        CHECK_EQ(std::uint16_t(42), toml::try_get<std::uint16_t>(as_const(v)).unwrap());
+
+        value_type v1(v);
+        value_type v2(v);
+        value_type v3(v);
+        value_type v4(v);
+        value_type v5(v);
+        value_type v6(v);
+        value_type v7(v);
+        value_type v8(v);
+        value_type v9(v);
+
+        CHECK_EQ(int(42),           toml::try_get<int          >(v1).unwrap());
+        CHECK_EQ(short(42),         toml::try_get<short        >(v2).unwrap());
+        CHECK_EQ(char(42),          toml::try_get<char         >(v3).unwrap());
+        CHECK_EQ(unsigned(42),      toml::try_get<unsigned     >(v4).unwrap());
+        CHECK_EQ(long(42),          toml::try_get<long         >(v5).unwrap());
+        CHECK_EQ(std::int64_t(42),  toml::try_get<std::int64_t >(v6).unwrap());
+        CHECK_EQ(std::uint64_t(42), toml::try_get<std::uint64_t>(v7).unwrap());
+        CHECK_EQ(std::int16_t(42),  toml::try_get<std::int16_t >(v8).unwrap());
+        CHECK_EQ(std::uint16_t(42), toml::try_get<std::uint16_t>(v9).unwrap());
+    }
+}
+
+TEST_CASE("testing toml::try_get<floating-like>")
+{
+    using value_type = toml::value;
+    {
+        const double ref(3.14);
+
+        value_type v(ref);
+        CHECK_EQ(static_cast<float      >(ref), toml::try_get<float      >(v).unwrap());
+        CHECK_EQ(                         ref , toml::try_get<double     >(v).unwrap());
+        CHECK_EQ(static_cast<long double>(ref), toml::try_get<long double>(v).unwrap());
+
+        value_type v1(ref);
+        value_type v2(ref);
+        value_type v3(ref);
+        CHECK_EQ(static_cast<float      >(ref), toml::try_get<float      >(std::move(v1)).unwrap());
+        CHECK_EQ(                         ref , toml::try_get<double     >(std::move(v2)).unwrap());
+        CHECK_EQ(static_cast<long double>(ref), toml::try_get<long double>(std::move(v3)).unwrap());
+    }
+}
+
+#if TOML11_CPLUSPLUS_STANDARD_VERSION >= 201703L
+TEST_CASE("testing toml::try_get<string-like>")
+{
+    using value_type = toml::value;
+    {
+        value_type v("foo");
+        CHECK_EQ("foo", toml::try_get<std::string_view>(v).unwrap());
+    }
+}
+#endif
+
+TEST_CASE("testing toml::try_get<array-like>")
+{
+    using value_type = toml::value;
+    {
+        const value_type v(toml::array{42, 54, 69, 72});
+
+        const std::vector<int>         vec = toml::try_get<std::vector<int>>(v).unwrap();
+        const std::list<short>         lst = toml::try_get<std::list<short>>(v).unwrap();
+        const std::deque<std::int64_t> deq = toml::try_get<std::deque<std::int64_t>>(v).unwrap();
+
+        CHECK_EQ(42, vec.at(0));
+        CHECK_EQ(54, vec.at(1));
+        CHECK_EQ(69, vec.at(2));
+        CHECK_EQ(72, vec.at(3));
+
+        std::list<short>::const_iterator iter = lst.begin();
+        CHECK_EQ(static_cast<short>(42), *(iter++));
+        CHECK_EQ(static_cast<short>(54), *(iter++));
+        CHECK_EQ(static_cast<short>(69), *(iter++));
+        CHECK_EQ(static_cast<short>(72), *(iter++));
+
+        CHECK_EQ(static_cast<std::int64_t>(42), deq.at(0));
+        CHECK_EQ(static_cast<std::int64_t>(54), deq.at(1));
+        CHECK_EQ(static_cast<std::int64_t>(69), deq.at(2));
+        CHECK_EQ(static_cast<std::int64_t>(72), deq.at(3));
+
+        std::array<int, 4> ary = toml::try_get<std::array<int, 4>>(v).unwrap();
+        CHECK_EQ(42, ary.at(0));
+        CHECK_EQ(54, ary.at(1));
+        CHECK_EQ(69, ary.at(2));
+        CHECK_EQ(72, ary.at(3));
+
+        std::tuple<int, short, unsigned, long> tpl =
+            toml::try_get<std::tuple<int, short, unsigned, long>>(v).unwrap();
+        CHECK_EQ(                      42 , std::get<0>(tpl));
+        CHECK_EQ(static_cast<short   >(54), std::get<1>(tpl));
+        CHECK_EQ(static_cast<unsigned>(69), std::get<2>(tpl));
+        CHECK_EQ(static_cast<long    >(72), std::get<3>(tpl));
+
+        const value_type p(toml::array{3.14, 2.71});
+        std::pair<double, double> pr = toml::try_get<std::pair<double, double> >(p).unwrap();
+        CHECK_EQ(3.14, pr.first);
+        CHECK_EQ(2.71, pr.second);
+    }
+
+    {
+        value_type v(toml::array{42, 54, 69, 72});
+        const std::vector<int> vec = toml::try_get<std::vector<int>>(std::move(v)).unwrap();
+        CHECK_EQ(42, vec.at(0));
+        CHECK_EQ(54, vec.at(1));
+        CHECK_EQ(69, vec.at(2));
+        CHECK_EQ(72, vec.at(3));
+    }
+    {
+        value_type v(toml::array{42, 54, 69, 72});
+        const std::deque<int> deq = toml::try_get<std::deque<int>>(std::move(v)).unwrap();
+        CHECK_EQ(42, deq.at(0));
+        CHECK_EQ(54, deq.at(1));
+        CHECK_EQ(69, deq.at(2));
+        CHECK_EQ(72, deq.at(3));
+    }
+    {
+        value_type v(toml::array{42, 54, 69, 72});
+        const std::list<int> lst = toml::try_get<std::list<int>>(std::move(v)).unwrap();
+        std::list<int>::const_iterator iter = lst.begin();
+        CHECK_EQ(42, *(iter++));
+        CHECK_EQ(54, *(iter++));
+        CHECK_EQ(69, *(iter++));
+        CHECK_EQ(72, *(iter++));
+    }
+    {
+        value_type v(toml::array{42, 54, 69, 72});
+        std::array<int, 4> ary = toml::try_get<std::array<int, 4>>(std::move(v)).unwrap();
+        CHECK_EQ(42, ary.at(0));
+        CHECK_EQ(54, ary.at(1));
+        CHECK_EQ(69, ary.at(2));
+        CHECK_EQ(72, ary.at(3));
+    }
+    {
+        value_type v(toml::array{42, 54, 69, 72});
+        std::tuple<int, short, unsigned, long> tpl =
+            toml::try_get<std::tuple<int, short, unsigned, long>>(std::move(v)).unwrap();
+        CHECK_EQ(                      42 , std::get<0>(tpl));
+        CHECK_EQ(static_cast<short   >(54), std::get<1>(tpl));
+        CHECK_EQ(static_cast<unsigned>(69), std::get<2>(tpl));
+        CHECK_EQ(static_cast<long    >(72), std::get<3>(tpl));
+    }
+}
+
+TEST_CASE("testing toml::try_get<array-of-arrays>")
+{
+    using value_type = toml::value;
+    {
+        const value_type v1(toml::array{42, 54, 69, 72});
+        const value_type v2(toml::array{"foo", "bar", "baz"});
+        const value_type v (toml::array{v1, v2});
+
+        std::pair<std::vector<int>, std::vector<std::string>> p =
+            toml::try_get<std::pair<std::vector<int>, std::vector<std::string>>>(v).unwrap();
+
+        CHECK_EQ(p.first.size(), 4u);
+        CHECK_EQ(p.first.at(0), 42);
+        CHECK_EQ(p.first.at(1), 54);
+        CHECK_EQ(p.first.at(2), 69);
+        CHECK_EQ(p.first.at(3), 72);
+
+        CHECK_EQ(p.second.size(), 3u);
+        CHECK_EQ(p.second.at(0), "foo");
+        CHECK_EQ(p.second.at(1), "bar");
+        CHECK_EQ(p.second.at(2), "baz");
+
+        std::tuple<std::vector<int>, std::vector<std::string>> t =
+            toml::try_get<std::tuple<std::vector<int>, std::vector<std::string>>>(v).unwrap();
+
+        CHECK_EQ(std::get<0>(t).at(0), 42);
+        CHECK_EQ(std::get<0>(t).at(1), 54);
+        CHECK_EQ(std::get<0>(t).at(2), 69);
+        CHECK_EQ(std::get<0>(t).at(3), 72);
+
+        CHECK_EQ(std::get<1>(t).at(0), "foo");
+        CHECK_EQ(std::get<1>(t).at(1), "bar");
+        CHECK_EQ(std::get<1>(t).at(2), "baz");
+    }
+    {
+        const value_type v1(toml::array{42, 54, 69, 72});
+        const value_type v2(toml::array{"foo", "bar", "baz"});
+        value_type       v (toml::array{v1, v2});
+
+        std::pair<std::vector<int>, std::vector<std::string>> p =
+            toml::try_get<std::pair<std::vector<int>, std::vector<std::string>>>(std::move(v)).unwrap();
+
+        CHECK_EQ(p.first.size(), 4u);
+        CHECK_EQ(p.first.at(0), 42);
+        CHECK_EQ(p.first.at(1), 54);
+        CHECK_EQ(p.first.at(2), 69);
+        CHECK_EQ(p.first.at(3), 72);
+
+        CHECK_EQ(p.second.size(), 3u);
+        CHECK_EQ(p.second.at(0), "foo");
+        CHECK_EQ(p.second.at(1), "bar");
+        CHECK_EQ(p.second.at(2), "baz");
+    }
+}
+
+TEST_CASE("testing toml::try_get<table-like>")
+{
+    using value_type = toml::value;
+    {
+        const value_type v1(toml::table{
+                {"key1", 1},
+                {"key2", 2},
+                {"key3", 3},
+                {"key4", 4}
+            });
+
+        const auto v = toml::try_get<std::map<std::string, int>>(v1).unwrap();
+        CHECK_EQ(v.at("key1"), 1);
+        CHECK_EQ(v.at("key2"), 2);
+        CHECK_EQ(v.at("key3"), 3);
+        CHECK_EQ(v.at("key4"), 4);
+    }
+    {
+        value_type v1(toml::table{
+                {"key1", 1},
+                {"key2", 2},
+                {"key3", 3},
+                {"key4", 4}
+            });
+        const auto v = toml::try_get<std::map<std::string, int>>(std::move(v1)).unwrap();
+        CHECK_EQ(v.at("key1"), 1);
+        CHECK_EQ(v.at("key2"), 2);
+        CHECK_EQ(v.at("key3"), 3);
+        CHECK_EQ(v.at("key4"), 4);
+    }
+}
+
+TEST_CASE("testing toml::try_get<time_point>(local_date)")
+{
+    using value_type = toml::value;
+
+    value_type v1(toml::local_date{2018, toml::month_t::Apr, 1});
+    const auto date = std::chrono::system_clock::to_time_t(
+            toml::try_get<std::chrono::system_clock::time_point>(v1).unwrap());
+
+    std::tm t;
+    t.tm_year = 2018 - 1900;
+    t.tm_mon  = 4    - 1;
+    t.tm_mday = 1;
+    t.tm_hour = 0;
+    t.tm_min  = 0;
+    t.tm_sec  = 0;
+    t.tm_isdst = -1;
+    const auto c = std::mktime(&t);
+    CHECK_EQ(c, date);
+}
+
+TEST_CASE("testing toml::try_get<duration>")
+{
+    using value_type = toml::value;
+
+    value_type v1(toml::local_time{12, 30, 45});
+    const auto time = toml::try_get<std::chrono::seconds>(v1).unwrap();
+    const bool result = time == std::chrono::hours(12)   +
+                                std::chrono::minutes(30) +
+                                std::chrono::seconds(45);
+    CHECK_UNARY(result);
+}
+
+TEST_CASE("testing toml::try_get<time_point>(local_datetime)")
+{
+    using value_type = toml::value;
+
+    value_type v1(toml::local_datetime(
+                toml::local_date{2018, toml::month_t::Apr, 1},
+                toml::local_time{12, 30, 45}));
+
+    const auto date = std::chrono::system_clock::to_time_t(
+            toml::try_get<std::chrono::system_clock::time_point>(v1).unwrap());
+
+    std::tm t;
+    t.tm_year = 2018 - 1900;
+    t.tm_mon  = 4    - 1;
+    t.tm_mday = 1;
+    t.tm_hour = 12;
+    t.tm_min  = 30;
+    t.tm_sec  = 45;
+    t.tm_isdst = -1;
+    const auto c = std::mktime(&t);
+    CHECK_EQ(c, date);
+}
+
+TEST_CASE("testing toml::try_get<time_point>(offset_datetime)")
+{
+    using value_type = toml::value;
+    {
+        value_type v1(toml::offset_datetime(
+                    toml::local_date{2018, toml::month_t::Apr, 1},
+                    toml::local_time{12, 30, 0},
+                    toml::time_offset{9, 0}));
+        //    2018-04-01T12:30:00+09:00
+        // == 2018-04-01T03:30:00Z
+
+        const auto date = toml::try_get<std::chrono::system_clock::time_point>(v1).unwrap();
+        const auto timet = std::chrono::system_clock::to_time_t(date);
+
+        // get time_t as gmtime (2018-04-01T03:30:00Z)
+        const auto tm = toml::detail::gmtime_s(std::addressof(timet));
+        CHECK_EQ(tm.tm_year + 1900, 2018);
+        CHECK_EQ(tm.tm_mon  + 1,       4);
+        CHECK_EQ(tm.tm_mday,           1);
+        CHECK_EQ(tm.tm_hour,           3);
+        CHECK_EQ(tm.tm_min,           30);
+        CHECK_EQ(tm.tm_sec,            0);
+    }
+
+    {
+        value_type v1(toml::offset_datetime(
+                    toml::local_date{2018, toml::month_t::Apr, 1},
+                    toml::local_time{12, 30, 0},
+                    toml::time_offset{-8, 0}));
+        //    2018-04-01T12:30:00-08:00
+        //, 2018-04-01T20:30:00Z
+
+        const auto date = toml::try_get<std::chrono::system_clock::time_point>(v1).unwrap();
+        const auto timet = std::chrono::system_clock::to_time_t(date);
+
+        // get time_t as gmtime (2018-04-01T03:30:00Z)
+        const auto tm = toml::detail::gmtime_s(std::addressof(timet));
+        CHECK_EQ(tm.tm_year + 1900, 2018);
+        CHECK_EQ(tm.tm_mon  + 1,       4);
+        CHECK_EQ(tm.tm_mday,           1);
+        CHECK_EQ(tm.tm_hour,          20);
+        CHECK_EQ(tm.tm_min,           30);
+        CHECK_EQ(tm.tm_sec,            0);
+    }
+}

tests/test_value.cpp

@@ -1062,21 +1062,89 @@ TEST_CASE("testing array-accessors")
 {
     toml::value x({true, 42, "hoge"});
 
+    // at
+
     CHECK_UNARY(x.at(0).is_boolean());
     CHECK_UNARY(x.at(1).is_integer());
     CHECK_UNARY(x.at(2).is_string());
+    CHECK_EQ(x.at(0).as_boolean(), true);
+    CHECK_EQ(x.at(1).as_integer(), 42);
+    CHECK_EQ(x.at(2).as_string(),  std::string("hoge"));
+    CHECK_THROWS_AS(x.at(3), std::out_of_range);
 
     CHECK_UNARY(as_const(x).at(0).is_boolean());
     CHECK_UNARY(as_const(x).at(1).is_integer());
     CHECK_UNARY(as_const(x).at(2).is_string());
-
-    CHECK_EQ(x.at(0).as_boolean(), true);
-    CHECK_EQ(x.at(1).as_integer(), 42);
-    CHECK_EQ(x.at(2).as_string(),  std::string("hoge"));
-
     CHECK_EQ(as_const(x).at(0).as_boolean(), true);
     CHECK_EQ(as_const(x).at(1).as_integer(), 42);
     CHECK_EQ(as_const(x).at(2).as_string(),  std::string("hoge"));
+    CHECK_THROWS_AS(as_const(x).at(3), std::out_of_range);
+
+    // update through at
+
+    x.at(0) = false;
+    x.at(1) = 6 * 9;
+    x.at(2) = 3.14;
+
+    CHECK_UNARY(x.at(0).is_boolean());
+    CHECK_UNARY(x.at(1).is_integer());
+    CHECK_UNARY(x.at(2).is_floating());
+    CHECK_EQ(x.at(0).as_boolean(), false);
+    CHECK_EQ(x.at(1).as_integer(), 6*9);
+    CHECK_EQ(x.at(2).as_floating(),  3.14);
+
+    x.at(0) = true;
+    x.at(1) = 42;
+    x.at(2) = "hoge";
+
+    // try_at
+
+    CHECK_UNARY(x.try_at(0).is_ok());
+    CHECK_UNARY(x.try_at(1).is_ok());
+    CHECK_UNARY(x.try_at(2).is_ok());
+    CHECK_UNARY(x.try_at(0).as_ok().is_boolean());
+    CHECK_UNARY(x.try_at(1).as_ok().is_integer());
+    CHECK_UNARY(x.try_at(2).as_ok().is_string());
+    CHECK_UNARY_FALSE(x.try_at(0).is_err());
+    CHECK_UNARY_FALSE(x.try_at(1).is_err());
+    CHECK_UNARY_FALSE(x.try_at(2).is_err());
+    CHECK_EQ(x.try_at(0).as_ok().as_boolean(), true);
+    CHECK_EQ(x.try_at(1).as_ok().as_integer(), 42);
+    CHECK_EQ(x.try_at(2).as_ok().as_string(),  std::string("hoge"));
+    CHECK_UNARY(x.try_at(3).is_err());
+
+    CHECK_UNARY(as_const(x).try_at(0).is_ok());
+    CHECK_UNARY(as_const(x).try_at(1).is_ok());
+    CHECK_UNARY(as_const(x).try_at(2).is_ok());
+    CHECK_UNARY(as_const(x).try_at(0).as_ok().is_boolean());
+    CHECK_UNARY(as_const(x).try_at(1).as_ok().is_integer());
+    CHECK_UNARY(as_const(x).try_at(2).as_ok().is_string());
+    CHECK_UNARY_FALSE(as_const(x).try_at(0).is_err());
+    CHECK_UNARY_FALSE(as_const(x).try_at(1).is_err());
+    CHECK_UNARY_FALSE(as_const(x).try_at(2).is_err());
+    CHECK_EQ(as_const(x).try_at(0).as_ok().as_boolean(), true);
+    CHECK_EQ(as_const(x).try_at(1).as_ok().as_integer(), 42);
+    CHECK_EQ(as_const(x).try_at(2).as_ok().as_string(),  std::string("hoge"));
+    CHECK_UNARY(as_const(x).try_at(3).is_err());
+
+    // update through try_at
+
+    x.try_at(0).as_ok() = false;
+    x.try_at(1).as_ok() = 6 * 9;
+    x.try_at(2).as_ok() = 3.14;
+
+    CHECK_UNARY(x.at(0).is_boolean());
+    CHECK_UNARY(x.at(1).is_integer());
+    CHECK_UNARY(x.at(2).is_floating());
+    CHECK_EQ(x.at(0).as_boolean(), false);
+    CHECK_EQ(x.at(1).as_integer(), 6*9);
+    CHECK_EQ(x.at(2).as_floating(),  3.14);
+
+    x.try_at(0).as_ok() = true;
+    x.try_at(1).as_ok() = 42;
+    x.try_at(2).as_ok() = "hoge";
+
+    // operator[]
 
     CHECK_UNARY(x[0].is_boolean());
     CHECK_UNARY(x[1].is_integer());
@@ -1086,6 +1154,8 @@ TEST_CASE("testing array-accessors")
     CHECK_EQ(x[1].as_integer(), 42);
     CHECK_EQ(x[2].as_string(),  std::string("hoge"));
 
+    // -----------------------------------------------------------------------
+
     const toml::value v1(3.14);
     toml::value v2(2.71);
 
@@ -1143,13 +1213,83 @@ TEST_CASE("testing table-accessors")
     CHECK_EQ(x.count("d"), 0);
     CHECK_EQ(x.count("e"), 0);
 
+    // at
+
     CHECK_UNARY(x.at("a").is_boolean());
     CHECK_UNARY(x.at("b").is_integer());
     CHECK_UNARY(x.at("c").is_string());
-
     CHECK_EQ(x.at("a").as_boolean(), true);
     CHECK_EQ(x.at("b").as_integer(), 42);
     CHECK_EQ(x.at("c").as_string(),  std::string("hoge"));
+    CHECK_THROWS_AS(x.at("d"), std::out_of_range);
+
+    CHECK_UNARY(as_const(x).at("a").is_boolean());
+    CHECK_UNARY(as_const(x).at("b").is_integer());
+    CHECK_UNARY(as_const(x).at("c").is_string());
+    CHECK_EQ(as_const(x).at("a").as_boolean(), true);
+    CHECK_EQ(as_const(x).at("b").as_integer(), 42);
+    CHECK_EQ(as_const(x).at("c").as_string(),  std::string("hoge"));
+    CHECK_THROWS_AS(as_const(x).at("d"), std::out_of_range);
+
+    // rewrite using at
+
+    x.at("a") = false;
+    x.at("b") = 6*9;
+    x.at("c") = 3.14;
+
+    CHECK_UNARY(x.at("a").is_boolean());
+    CHECK_UNARY(x.at("b").is_integer());
+    CHECK_UNARY(x.at("c").is_floating());
+    CHECK_EQ(x.at("a").as_boolean(), false);
+    CHECK_EQ(x.at("b").as_integer(), 6*9);
+    CHECK_EQ(x.at("c").as_floating(), 3.14);
+
+    x.at("a") = true;
+    x.at("b") = 42;
+    x.at("c") = "hoge";
+
+    // try_at
+
+    CHECK_UNARY(x.try_at("a").is_ok());
+    CHECK_UNARY(x.try_at("b").is_ok());
+    CHECK_UNARY(x.try_at("c").is_ok());
+    CHECK_UNARY(x.try_at("a").as_ok().is_boolean());
+    CHECK_UNARY(x.try_at("b").as_ok().is_integer());
+    CHECK_UNARY(x.try_at("c").as_ok().is_string());
+    CHECK_EQ(x.try_at("a").as_ok().as_boolean(), true);
+    CHECK_EQ(x.try_at("b").as_ok().as_integer(), 42);
+    CHECK_EQ(x.try_at("c").as_ok().as_string(),  std::string("hoge"));
+    CHECK_UNARY(x.try_at("d").is_err());
+
+    CHECK_UNARY(as_const(x).try_at("a").is_ok());
+    CHECK_UNARY(as_const(x).try_at("b").is_ok());
+    CHECK_UNARY(as_const(x).try_at("c").is_ok());
+    CHECK_UNARY(as_const(x).try_at("a").as_ok().is_boolean());
+    CHECK_UNARY(as_const(x).try_at("b").as_ok().is_integer());
+    CHECK_UNARY(as_const(x).try_at("c").as_ok().is_string());
+    CHECK_EQ(as_const(x).try_at("a").as_ok().as_boolean(), true);
+    CHECK_EQ(as_const(x).try_at("b").as_ok().as_integer(), 42);
+    CHECK_EQ(as_const(x).try_at("c").as_ok().as_string(),  std::string("hoge"));
+    CHECK_UNARY(as_const(x).try_at("d").is_err());
+
+    // rewrite using try_at
+
+    x.try_at("a").as_ok() = false;
+    x.try_at("b").as_ok() = 6*9;
+    x.try_at("c").as_ok() = 3.14;
+
+    CHECK_UNARY(x.at("a").is_boolean());
+    CHECK_UNARY(x.at("b").is_integer());
+    CHECK_UNARY(x.at("c").is_floating());
+    CHECK_EQ(x.at("a").as_boolean(), false);
+    CHECK_EQ(x.at("b").as_integer(), 6*9);
+    CHECK_EQ(x.at("c").as_floating(), 3.14);
+
+    x.try_at("a").as_ok() = true;
+    x.try_at("b").as_ok() = 42;
+    x.try_at("c").as_ok() = "hoge";
+
+    // operator[]
 
     CHECK_UNARY(x["a"].is_boolean());
     CHECK_UNARY(x["b"].is_integer());