doc: update Fuzzy search section

Add the following
- find_fuzzy<T>(val, "key")
- find<T>(val, "key", FuzzyMatcher) to suggest typo
- levenstein_matcher

README.md

@@ -270,6 +270,46 @@ const auto color = toml::find<std::string>(data, "fruit", "physical", "color");
 const auto shape = toml::find<std::string>(data, "fruit", "physical", "shape");
 ```
 
+### Dotted keys
+
+TOML v0.5.0 has a new feature named "dotted keys".
+You can chain keys to represent the structure of the data.
+
+```toml
+physical.color = "orange"
+physical.shape = "round"
+```
+
+This is equivalent to the following.
+
+```toml
+[physical]
+color = "orange"
+shape = "round"
+```
+
+You can get both of the above tables with the same c++ code.
+
+```cpp
+const auto physical = toml::find(data, "physical");
+const auto color    = toml::find<std::string>(physical, "color");
+```
+
+The following code does not work for the above toml file.
+
+```cpp
+// XXX this does not work!
+const auto color = toml::find<std::string>(data, "physical.color");
+```
+
+The above code works with the following toml file.
+
+```toml
+"physical.color" = "orange"
+# equivalent to {"physical.color": "orange"},
+# NOT {"physical": {"color": "orange"}}.
+```
+
 ### In case of error
 
 If the value does not exist, `toml::find` throws an error with the location of
@@ -310,46 +350,77 @@ shared by `toml::value`s and remains on the heap memory. It is recommended to
 destruct all the `toml::value` classes after configuring your application
 if you have a large TOML file compared to the memory resource.
 
-### Dotted keys
+### Fuzzy Search
 
-TOML v0.5.0 has a new feature named "dotted keys".
+To find a value, you can use `find_fuzzy` instead of `find`.
-You can chain keys to represent the structure of the data.
 
 ```toml
-physical.color = "orange"
+[foobar]
-physical.shape = "round"
+# typo!
+anseer = 42
 ```
 
-This is equivalent to the following.
-
-```toml
-[physical]
-color = "orange"
-shape = "round"
-```
-
-You can get both of the above tables with the same c++ code.
-
 ```cpp
-const auto physical = toml::find(data, "physical");
+const auto data   = toml::parse("sample.toml");
-const auto color    = toml::find<std::string>(physical, "color");
+const auto foobar = toml::find(data, "foobar");
+const auto answer = toml::find_fuzzy<int>(data, "answer"); // it finds "anseer".
 ```
 
-The following code does not work for the above toml file.
+When the specified key is not found, `toml::find_fuzzy` calculates
+[levenstein distance](https://en.wikipedia.org/wiki/Levenshtein_distance)
+between the specified key and other keys.
+If it finds a key that is 1 away from the specified key by the Levenstein
+distance, it returns the corresponding value.
+
+To allow a more distant string, you can explicitly pass `toml::levenstein_matcher`
+to `find_fuzzy`.
 
 ```cpp
-// XXX this does not work!
+toml::levenstein_matcher lev(2); // allow distance <= 2
-const auto color = toml::find<std::string>(data, "physical.color");
+const auto answer = toml::find_fuzzy<int>(data, "answer", lev);
 ```
 
-The above code works with the following toml file.
+You can also use your own distance metric. Implement your `fuzzy_matcher` that
+has `operator()` that takes two strings and returns true if two strings resemble
+each other.
 
-```toml
+```cpp
-"physical.color" = "orange"
+struct fuzzy_matcher
-# equivalent to {"physical.color": "orange"},
+{
-# NOT {"physical": {"color": "orange"}}.
+    bool operator()(const std::string& lhs, const std::string& rhs) const
+    {
+        // return true if lhs matches with rhs.
+    }
+};
 ```
 
+If there are multiple keys that meets the condition, it throws `runtime_error`.
+
+However, in many cases, rather than just allowing typographical errors,
+you will want to suggest it and encouledge users to correct it.
+
+If you pass a `fuzzy_matcher` to `toml::find`, a suggestion will be displayed
+in the error message.
+
+```cpp
+toml::levenstein_matcher lev(1); // finds keys within distance <= 1
+const auto answer = toml::find<int>(data, "answer", lev); // it throws!
+```
+
+```console
+terminate called after throwing an instance of 'std::out_of_range'
+  what():  [error] key "answer" not found.
+ --> hoge.toml
+ 1 | [foobar]
+   | ~~~~~~~~ in this table
+ ...
+ 2 | anseer = 42
+   |          ~~ did you mean this here?
+```
+
+Note: Currently, `find_fuzzy` and `find(value, key, matcher)` take only one key.
+The codes like `find_fuzzy(value, key1, key2, key3)` do not work.
+
 ## Casting a toml value
 
 ### `toml::get`

tests/CMakeLists.txt

@@ -27,6 +27,7 @@ set(TEST_NAMES
     test_get_or
     test_find
     test_find_or
+    test_find_fuzzy
     test_expect
     test_parse_file
     test_serialize_file

tests/test_find_fuzzy.cpp

@@ -0,0 +1,350 @@
+#define BOOST_TEST_MODULE "test_find_fuzzy"
+
+#ifdef UNITTEST_FRAMEWORK_LIBRARY_EXIST
+#include <boost/test/unit_test.hpp>
+#else
+#define BOOST_TEST_NO_LIB
+#include <boost/test/included/unit_test.hpp>
+#endif
+
+#include <toml.hpp>
+
+BOOST_AUTO_TEST_CASE(test_levenstein_distance)
+{
+    const toml::levenstein_matcher lev(1);
+
+    // distance == 0
+    {
+        const std::string s1("foobar");
+        const std::string s2 = s1;
+
+        BOOST_TEST(lev.distance(s1, s2) == 0);
+    }
+
+    {
+        const std::string s1("foobar");
+        const std::string s2("foobaz");
+
+        BOOST_TEST(lev.distance(s1, s2) == 1);
+    }
+    {
+        const std::string s1("foobar"); // insertion (+x)
+        const std::string s2("fooxbar");
+
+        BOOST_TEST(lev.distance(s1, s2) == 1);
+    }
+    {
+        const std::string s1("foobar");
+        const std::string s2("fooar"); // insertion(+b)
+
+        BOOST_TEST(lev.distance(s1, s2) == 1);
+    }
+
+    // distance > 1
+    {
+        const std::string s1("foobar");
+        const std::string s2("fooquux");
+
+        BOOST_TEST(lev.distance(s1, s2) == 4);
+    }
+    {
+        const std::string s1("foobar");
+        const std::string s2("fooqu");
+
+        BOOST_TEST(s1 != s2);
+        BOOST_TEST(lev.distance(s1, s2) == 3);
+    }
+}
+
+BOOST_AUTO_TEST_CASE(test_find_fuzzy)
+{
+    {
+        toml::value v{
+            {"keu", "value"} // typo! key -> keu
+        };
+
+        BOOST_TEST(toml::find_fuzzy(v, "key") == toml::value("value"));
+        BOOST_CHECK_THROW(toml::find_fuzzy(v, "kiwi"), std::out_of_range);
+
+        static_assert(std::is_same<
+                toml::value&, decltype(toml::find_fuzzy(v, "key"))>::value, "");
+
+        toml::find_fuzzy(v, "key") = "foobar";
+        BOOST_TEST(toml::find(v, "keu") == toml::value("foobar"));
+    }
+    {
+        const toml::value v{
+            {"keu", "value"} // typo! key -> keu
+        };
+
+        BOOST_TEST(toml::find_fuzzy(v, "key") == toml::value("value"));
+        BOOST_CHECK_THROW(toml::find_fuzzy(v, "kiwi"), std::out_of_range);
+
+        static_assert(std::is_same<
+                toml::value const&, decltype(toml::find_fuzzy(v, "key"))>::value, "");
+    }
+    {
+        toml::value v{
+            {"keu", "value"} // typo! key -> keu
+        };
+
+        BOOST_TEST(toml::find_fuzzy(std::move(v), "key") == toml::value("value"));
+
+        static_assert(std::is_same<
+                toml::value&&, decltype(toml::find_fuzzy(std::move(v), "key"))>::value, "");
+    }
+    {
+        toml::value v{
+            {"keu", "value"} // typo! key -> keu
+        };
+
+        BOOST_CHECK_THROW(toml::find_fuzzy(std::move(v), "kiwi"), std::out_of_range);
+
+        static_assert(std::is_same<
+                toml::value&&, decltype(toml::find_fuzzy(std::move(v), "key"))>::value, "");
+    }
+
+    // find with conversion
+
+    {
+        toml::value v{
+            {"keu", 42} // typo! key -> keu
+        };
+
+        BOOST_TEST(toml::find_fuzzy<int>(v, "key") == 42);
+        BOOST_CHECK_THROW(toml::find_fuzzy<int>(v, "kiwi"), std::out_of_range);
+
+        static_assert(std::is_same<int,
+                decltype(toml::find_fuzzy<int>(v, "key"))>::value, "");
+    }
+    {
+        const toml::value v{
+            {"keu", 42} // typo! key -> keu
+        };
+
+        BOOST_TEST(toml::find_fuzzy<int>(v, "key") == 42);
+        BOOST_CHECK_THROW(toml::find_fuzzy<int>(v, "kiwi"), std::out_of_range);
+
+        static_assert(std::is_same<int,
+                decltype(toml::find_fuzzy<int>(v, "key"))>::value, "");
+    }
+    {
+        toml::value v{
+            {"keu", 42} // typo! key -> keu
+        };
+
+        BOOST_TEST(toml::find_fuzzy<int>(std::move(v), "key") == 42);
+
+        static_assert(std::is_same<int,
+                decltype(toml::find_fuzzy<int>(std::move(v), "key"))>::value, "");
+    }
+    {
+        toml::value v{
+            {"keu", 42} // typo! key -> keu
+        };
+
+        BOOST_CHECK_THROW(toml::find_fuzzy<int>(std::move(v), "kiwi"), std::out_of_range);
+    }
+}
+
+BOOST_AUTO_TEST_CASE(test_find_fuzzy_throw)
+{
+    {
+        toml::value v{
+            {"keu", "value"}, // typo! key -> keu
+            {"ky", "value"}   // typo! key -> ky
+        };
+
+        BOOST_CHECK_THROW(toml::find_fuzzy(v, "key"), std::out_of_range);
+    }
+    {
+        const toml::value v{
+            {"keu", "value"}, // typo! key -> keu
+            {"ky", "value"}   // typo! key -> ky
+        };
+
+        BOOST_CHECK_THROW(toml::find_fuzzy(v, "key"), std::out_of_range);
+    }
+    {
+        toml::value v{
+            {"keu", "value"}, // typo! key -> keu
+            {"ky", "value"}   // typo! key -> ky
+        };
+
+        BOOST_CHECK_THROW(toml::find_fuzzy(std::move(v), "key"), std::out_of_range);
+    }
+
+    {
+        toml::value v{
+            {"keu", 42}, // typo! key -> keu
+            {"ky",  42}  // typo! key -> ky
+        };
+
+        BOOST_CHECK_THROW(toml::find_fuzzy<int>(v, "key"), std::out_of_range);
+    }
+    {
+        const toml::value v{
+            {"keu", 42}, // typo! key -> keu
+            {"ky",  42}  // typo! key -> ky
+        };
+
+        BOOST_CHECK_THROW(toml::find_fuzzy<int>(v, "key"), std::out_of_range);
+    }
+    {
+        toml::value v{
+            {"keu", 42}, // typo! key -> keu
+            {"ky",  42}  // typo! key -> ky
+        };
+
+        BOOST_CHECK_THROW(toml::find_fuzzy<int>(std::move(v), "key"), std::out_of_range);
+    }
+
+}
+
+BOOST_AUTO_TEST_CASE(test_find_throw_typo_aware_exception)
+{
+    using namespace toml::literals::toml_literals;
+    const toml::levenstein_matcher lev(1);
+    {
+        toml::value v = u8R"(
+            keu = "value"
+        )"_toml;
+
+        BOOST_CHECK_THROW(toml::find(v, "key", lev), std::out_of_range);
+        try
+        {
+            const auto& ret = toml::find(v, "key", lev);
+            (void)ret; // suppress unused variable
+        }
+        catch(const std::out_of_range& oor)
+        {
+            // exception.what() should include the typo-ed key name
+            const std::string what(oor.what());
+            BOOST_TEST(what.find("keu") != std::string::npos);
+
+//             std::cout << what << std::endl;
+        }
+        static_assert(std::is_same<
+                toml::value&, decltype(toml::find(v, "key"))>::value, "");
+    }
+    {
+        const toml::value v = u8R"(
+            keu = "value"
+        )"_toml;
+
+        BOOST_CHECK_THROW(toml::find(v, "key", lev), std::out_of_range);
+        try
+        {
+            const auto& ret = toml::find(v, "key", lev);
+            (void)ret;
+        }
+        catch(const std::out_of_range& oor)
+        {
+            // exception.what() should include the typo-ed key name
+            const std::string what(oor.what());
+            BOOST_TEST(what.find("keu") != std::string::npos);
+
+//             std::cout << what << std::endl;
+        }
+        static_assert(std::is_same<
+                toml::value const&, decltype(toml::find(v, "key"))>::value, "");
+    }
+    {
+        toml::value v = u8R"(
+            keu = "value"
+        )"_toml;
+
+        bool thrown = false; // since it moves, we need to check both once
+        try
+        {
+            const auto& ret = toml::find(std::move(v), "key", lev);
+            (void)ret;
+        }
+        catch(const std::out_of_range& oor)
+        {
+            // exception.what() should include the typo-ed key name
+            const std::string what(oor.what());
+            BOOST_TEST(what.find("keu") != std::string::npos);
+            thrown = true;
+
+//             std::cout << what << std::endl;
+        }
+        BOOST_TEST(thrown);
+        static_assert(std::is_same<
+                toml::value&, decltype(toml::find(v, "key"))>::value, "");
+    }
+}
+
+BOOST_AUTO_TEST_CASE(test_find_throw_conversion_typo_aware_exception)
+{
+    using namespace toml::literals::toml_literals;
+    const toml::levenstein_matcher lev(1);
+    {
+        toml::value v = u8R"(
+            keu = 42
+        )"_toml;
+
+        BOOST_CHECK_THROW(toml::find<int>(v, "key", lev), std::out_of_range);
+        try
+        {
+            const auto& ret = toml::find<int>(v, "key", lev);
+            (void)ret; // suppress unused variable
+        }
+        catch(const std::out_of_range& oor)
+        {
+            // exception.what() should include the typo-ed key name
+            const std::string what(oor.what());
+            BOOST_TEST(what.find("keu") != std::string::npos);
+
+//             std::cout << what << std::endl;
+        }
+        static_assert(std::is_same<int,
+                decltype(toml::find<int>(v, "key"))>::value, "");
+    }
+    {
+        const toml::value v = u8R"(
+            keu = 42
+        )"_toml;
+
+        BOOST_CHECK_THROW(toml::find<int>(v, "key", lev), std::out_of_range);
+        try
+        {
+            const auto& ret = toml::find<int>(v, "key", lev);
+            (void)ret;
+        }
+        catch(const std::out_of_range& oor)
+        {
+            // exception.what() should include the typo-ed key name
+            const std::string what(oor.what());
+            BOOST_TEST(what.find("keu") != std::string::npos);
+
+//             std::cout << what << std::endl;
+        }
+        static_assert(std::is_same<int,
+                decltype(toml::find<int>(v, "key"))>::value, "");
+    }
+    {
+        toml::value v = u8R"(
+            keu = 42
+        )"_toml;
+
+        bool thrown = false; // since it moves, we need to check both once
+        try
+        {
+            const auto& ret = toml::find<int>(std::move(v), "key", lev);
+            (void)ret;
+        }
+        catch(const std::out_of_range& oor)
+        {
+            // exception.what() should include the typo-ed key name
+            const std::string what(oor.what());
+            BOOST_TEST(what.find("keu") != std::string::npos);
+            thrown = true;
+
+//             std::cout << what << std::endl;
+        }
+        BOOST_TEST(thrown);
+        static_assert(std::is_same<int,
+                decltype(toml::find<int>(v, "key"))>::value, "");
+    }
+}

toml.hpp

@@ -37,5 +37,6 @@
 #include "toml/literal.hpp"
 #include "toml/serializer.hpp"
 #include "toml/get.hpp"
+#include "toml/find.hpp"
 
 #endif// TOML_FOR_MODERN_CPP

toml/find.hpp

@@ -0,0 +1,786 @@
+//     Copyright Toru Niina 2019.
+// Distributed under the MIT License.
+#ifndef TOML11_FIND_HPP
+#define TOML11_FIND_HPP
+#include "get.hpp"
+#include <numeric>
+
+namespace toml
+{
+
+// ----------------------------------------------------------------------------
+// these overloads do not require to set T. and returns value itself.
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V>
+basic_value<C, M, V> const& find(const basic_value<C, M, V>& v, const key& ky)
+{
+    const auto& tab = v.template cast<value_t::table>();
+    if(tab.count(ky) == 0)
+    {
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return tab.at(ky);
+}
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V>
+basic_value<C, M, V>& find(basic_value<C, M, V>& v, const key& ky)
+{
+    auto& tab = v.template cast<value_t::table>();
+    if(tab.count(ky) == 0)
+    {
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return tab.at(ky);
+}
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V>
+basic_value<C, M, V>&& find(basic_value<C, M, V>&& v, const key& ky)
+{
+    auto tab = std::move(v).as_table();
+    if(tab.count(ky) == 0)
+    {
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return std::move(tab.at(ky));
+}
+
+// ----------------------------------------------------------------------------
+// find<T>(value, key);
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+decltype(::toml::get<T>(std::declval<basic_value<C, M, V> const&>()))
+find(const basic_value<C, M, V>& v, const key& ky)
+{
+    const auto& tab = v.as_table();
+    if(tab.count(ky) == 0)
+    {
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return ::toml::get<T>(tab.at(ky));
+}
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&>()))
+find(basic_value<C, M, V>& v, const key& ky)
+{
+    auto& tab = v.as_table();
+    if(tab.count(ky) == 0)
+    {
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return ::toml::get<T>(tab.at(ky));
+}
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&&>()))
+find(basic_value<C, M, V>&& v, const key& ky)
+{
+    auto tab = std::move(v).as_table();
+    if(tab.count(ky) == 0)
+    {
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return ::toml::get<T>(std::move(tab.at(ky)));
+}
+
+// --------------------------------------------------------------------------
+// toml::find(toml::value, toml::key, Ts&& ... keys)
+
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename ... Ts>
+detail::enable_if_t<detail::conjunction<std::is_convertible<Ts, std::string>...
+    >::value, const basic_value<C, M, V>&>
+find(const basic_value<C, M, V>& v, const ::toml::key& ky, Ts&& ... keys)
+{
+    return ::toml::find(::toml::find(v, ky), std::forward<Ts>(keys)...);
+}
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename ... Ts>
+detail::enable_if_t<detail::conjunction<std::is_convertible<Ts, std::string>...
+    >::value, basic_value<C, M, V>&>
+find(basic_value<C, M, V>& v, const ::toml::key& ky, Ts&& ... keys)
+{
+    return ::toml::find(::toml::find(v, ky), std::forward<Ts>(keys)...);
+}
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename ... Ts>
+detail::enable_if_t<detail::conjunction<std::is_convertible<Ts, std::string>...
+    >::value, basic_value<C, M, V>&&>
+find(basic_value<C, M, V>&& v, const ::toml::key& ky, Ts&& ... keys)
+{
+    return ::toml::find(::toml::find(std::move(v), ky), std::forward<Ts>(keys)...);
+}
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename ... Ts>
+detail::enable_if_t<detail::conjunction<std::is_convertible<Ts, std::string>...
+    >::value, decltype(get<T>(std::declval<const basic_value<C, M, V>&>()))>
+find(const basic_value<C, M, V>& v, const ::toml::key& ky, Ts&& ... keys)
+{
+    return ::toml::find<T>(::toml::find(v, ky), std::forward<Ts>(keys)...);
+}
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename ... Ts>
+detail::enable_if_t<detail::conjunction<std::is_convertible<Ts, std::string>...
+    >::value, decltype(get<T>(std::declval<basic_value<C, M, V>&>()))>
+find(basic_value<C, M, V>& v, const ::toml::key& ky, Ts&& ... keys)
+{
+    return ::toml::find<T>(::toml::find(v, ky), std::forward<Ts>(keys)...);
+}
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename ... Ts>
+detail::enable_if_t<detail::conjunction<std::is_convertible<Ts, std::string>...
+    >::value, decltype(get<T>(std::declval<basic_value<C, M, V>&&>()))>
+find(basic_value<C, M, V>&& v, const ::toml::key& ky, Ts&& ... keys)
+{
+    return ::toml::find<T>(::toml::find(std::move(v), ky), std::forward<Ts>(keys)...);
+}
+
+// ===========================================================================
+// find_or(value, key, fallback)
+
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V>
+basic_value<C, M, V> const&
+find_or(const basic_value<C, M, V>& v, const key& ky,
+        const basic_value<C, M, V>& opt)
+{
+    if(!v.is_table()) {return opt;}
+    const auto& tab = v.as_table();
+    if(tab.count(ky) == 0) {return opt;}
+    return tab.at(ky);
+}
+
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V>
+basic_value<C, M, V>&
+find_or(basic_value<C, M, V>& v, const toml::key& ky, basic_value<C, M, V>& opt)
+{
+    if(!v.is_table()) {return opt;}
+    auto& tab = v.as_table();
+    if(tab.count(ky) == 0) {return opt;}
+    return tab[ky];
+}
+
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V>
+basic_value<C, M, V>
+find_or(basic_value<C, M, V>&& v, const toml::key& ky, basic_value<C, M, V>&& opt)
+{
+    if(!v.is_table()) {return std::move(opt);}
+    auto tab = std::move(v).as_table();
+    if(tab.count(ky) == 0) {return std::move(opt);}
+    return std::move(tab[ky]);
+}
+
+// ---------------------------------------------------------------------------
+// exact types (return type can be a reference)
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+detail::enable_if_t<
+    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T> const&
+find_or(const basic_value<C, M, V>& v, const key& ky, const T& opt)
+{
+    if(!v.is_table()) {return opt;}
+    const auto& tab = v.as_table();
+    if(tab.count(ky) == 0) {return opt;}
+    return get_or(tab.at(ky), opt);
+}
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+detail::enable_if_t<
+    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T>&
+find_or(basic_value<C, M, V>& v, const toml::key& ky, T& opt)
+{
+    if(!v.is_table()) {return opt;}
+    auto& tab = v.as_table();
+    if(tab.count(ky) == 0) {return opt;}
+    return get_or(tab[ky], opt);
+}
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+detail::enable_if_t<
+    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T>&&
+find_or(basic_value<C, M, V>&& v, const toml::key& ky, T&& opt)
+{
+    if(!v.is_table()) {return std::forward<T>(opt);}
+    auto tab = std::move(v).as_table();
+    if(tab.count(ky) == 0) {return std::forward<T>(opt);}
+    return get_or(std::move(tab[ky]), std::forward<T>(opt));
+}
+
+// ---------------------------------------------------------------------------
+// std::string (return type can be a reference)
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+detail::enable_if_t<std::is_same<T, std::string>::value, std::string> const&
+find_or(const basic_value<C, M, V>& v, const key& ky, const T& opt)
+{
+    if(!v.is_table()) {return opt;}
+    const auto& tab = v.as_table();
+    if(tab.count(ky) == 0) {return opt;}
+    return get_or(tab.at(ky), opt);
+}
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+detail::enable_if_t<std::is_same<T, std::string>::value, std::string>&
+find_or(basic_value<C, M, V>& v, const toml::key& ky, T& opt)
+{
+    if(!v.is_table()) {return opt;}
+    auto& tab = v.as_table();
+    if(tab.count(ky) == 0) {return opt;}
+    return get_or(tab.at(ky), opt);
+}
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+detail::enable_if_t<std::is_same<T, std::string>::value, std::string>
+find_or(basic_value<C, M, V>&& v, const toml::key& ky, T&& opt)
+{
+    if(!v.is_table()) {return std::forward<T>(opt);}
+    auto tab = std::move(v).as_table();
+    if(tab.count(ky) == 0) {return std::forward<T>(opt);}
+    return get_or(std::move(tab.at(ky)), std::forward<T>(opt));
+}
+
+// ---------------------------------------------------------------------------
+// string literal (deduced as std::string)
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+detail::enable_if_t<
+    detail::is_string_literal<typename std::remove_reference<T>::type>::value,
+    std::string>
+find_or(const basic_value<C, M, V>& v, const toml::key& ky, T&& opt)
+{
+    if(!v.is_table()) {return std::string(opt);}
+    const auto& tab = v.as_table();
+    if(tab.count(ky) == 0) {return std::string(opt);}
+    return get_or(tab.at(ky), std::forward<T>(opt));
+}
+
+// ---------------------------------------------------------------------------
+// others (require type conversion and return type cannot be lvalue reference)
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+detail::enable_if_t<detail::conjunction<
+    // T is not an exact toml type
+    detail::negation<detail::is_exact_toml_type<
+        typename std::remove_cv<typename std::remove_reference<T>::type>::type,
+        basic_value<C, M, V>>>,
+    // T is not std::string
+    detail::negation<std::is_same<std::string,
+        typename std::remove_cv<typename std::remove_reference<T>::type>::type>>,
+    // T is not a string literal
+    detail::negation<detail::is_string_literal<
+        typename std::remove_reference<T>::type>>
+    >::value, typename std::remove_cv<typename std::remove_reference<T>::type>::type>
+find_or(const basic_value<C, M, V>& v, const toml::key& ky, T&& opt)
+{
+    if(!v.is_table()) {return std::forward<T>(opt);}
+    const auto& tab = v.as_table();
+    if(tab.count(ky) == 0) {return std::forward<T>(opt);}
+    return get_or(tab.at(ky), std::forward<T>(opt));
+}
+
+// ============================================================================
+// expect
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+result<T, std::string> expect(const basic_value<C, M, V>& v) noexcept
+{
+    try
+    {
+        return ok(get<T>(v));
+    }
+    catch(const std::exception& e)
+    {
+        return err(e.what());
+    }
+}
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V>
+result<T, std::string>
+expect(const basic_value<C, M, V>& v, const toml::key& k) noexcept
+{
+    try
+    {
+        return ok(find<T>(v, k));
+    }
+    catch(const std::exception& e)
+    {
+        return err(e.what());
+    }
+}
+template<typename T, typename Table>
+detail::enable_if_t<detail::conjunction<
+    detail::is_map<Table>, detail::is_basic_value<typename Table::mapped_type>
+    >::value, result<T, std::string>>
+expect(const Table& t, const toml::key& k,
+       std::string tablename = "unknown table") noexcept
+{
+    try
+    {
+        return ok(find<T>(t, k, std::move(tablename)));
+    }
+    catch(const std::exception& e)
+    {
+        return err(e.what());
+    }
+}
+
+// ===========================================================================
+// find_fuzzy
+
+// ---------------------------------------------------------------------------
+// default fuzzy matcher; levenstein distance (all cost is 1)
+
+struct levenstein_matcher
+{
+    levenstein_matcher(): tolerance(1) {}
+    levenstein_matcher(const std::uint32_t tol): tolerance(tol) {}
+    ~levenstein_matcher() = default;
+    levenstein_matcher(levenstein_matcher const&) = default;
+    levenstein_matcher(levenstein_matcher &&)     = default;
+    levenstein_matcher& operator=(levenstein_matcher const&) = default;
+    levenstein_matcher& operator=(levenstein_matcher &&)     = default;
+
+    template<typename charT, typename traitsT, typename Alloc1, typename Alloc2>
+    bool operator()(const std::basic_string<charT, traitsT, Alloc1>& lhs,
+                    const std::basic_string<charT, traitsT, Alloc2>& rhs) const
+    {
+        return this->distance(lhs, rhs) <= this->tolerance;
+    }
+
+    template<typename charT, typename traitsT, typename Alloc1, typename Alloc2>
+    std::uint32_t distance(
+            const std::basic_string<charT, traitsT, Alloc1>& lhs,
+            const std::basic_string<charT, traitsT, Alloc2>& rhs) const
+    {
+        // force `lhs.size() <= rhs.size()`
+        if(lhs.size() > rhs.size()) {return this->distance(rhs, lhs);}
+
+        std::vector<std::uint32_t> matrix(lhs.size() + 1u);
+        std::iota(matrix.begin(), matrix.end(), 0);
+
+        for(const charT r : rhs)
+        {
+            std::uint32_t prev_diag = matrix.front();
+            matrix.front() += 1;
+
+            for(std::size_t i=0; i<lhs.size(); ++i)
+            {
+                const charT l = lhs[i];
+                if(traitsT::eq(l, r))
+                {
+                    std::swap(matrix[i+1], prev_diag);
+                }
+                else
+                {
+                    const auto tmp = matrix[i+1];
+                    matrix[i+1] = std::min(prev_diag, std::min(matrix[i], matrix[i+1])) + 1;
+                    prev_diag = tmp;
+                }
+            }
+        }
+        return matrix.back();
+    }
+
+  private:
+    std::uint32_t tolerance;
+};
+
+// ---------------------------------------------------------------------------
+// toml::find_fuzzy<T>(v, "tablename", FuzzyMatcher);
+
+namespace detail
+{
+template<typename Iterator, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher>
+Iterator find_unique(
+        Iterator iter, const Iterator end, const basic_value<C, M, V>& v,
+        const toml::key& k, const FuzzyMatcher& match)
+{
+    Iterator found = end;
+    for(; iter != end; ++iter)
+    {
+        if(match(iter->first, k))
+        {
+            if(found != end)
+            {
+                throw std::out_of_range(detail::format_underline(
+                    concat_to_string("[error] key \"", k, "\" not found."),
+                    {
+                        {std::addressof(detail::get_region(v)),"in this table"},
+                        {std::addressof(detail::get_region(found->second)),
+                         "did you mean this here?"},
+                        {std::addressof(detail::get_region(iter->second)),
+                         "or this?"}
+                    }));
+            }
+            found = iter;
+        }
+    }
+    return found;
+}
+} // detail
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher = levenstein_matcher>
+auto find_fuzzy(const basic_value<C, M, V>& v, const key& ky,
+                const FuzzyMatcher match = levenstein_matcher(1))
+    -> decltype(find<T>(std::declval<const basic_value<C, M, V>&>(), ky))
+{
+    try
+    {
+        return find<T>(v, ky);
+    }
+    catch(const std::out_of_range& oor)
+    {
+        const auto& t = v.as_table();
+        const auto found = detail::find_unique(t.begin(), t.end(), v, ky, match);
+        if(found != t.end())
+        {
+            return get<T>(found->second);
+        }
+        throw;
+    }
+}
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher = levenstein_matcher>
+auto find_fuzzy(basic_value<C, M, V>& v, const key& ky,
+                const FuzzyMatcher match = levenstein_matcher(1))
+    -> decltype(find<T>(std::declval<basic_value<C, M, V>&>(), ky))
+{
+    try
+    {
+        return find<T>(v, ky);
+    }
+    catch(const std::out_of_range& oor)
+    {
+        auto& t = v.as_table();
+        const auto found = detail::find_unique(t.begin(), t.end(), v, ky, match);
+        if(found != t.end())
+        {
+            return get<T>(found->second);
+        }
+        throw;
+    }
+}
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher = levenstein_matcher>
+auto find_fuzzy(basic_value<C, M, V>&& v_, const key& ky,
+                const FuzzyMatcher match = levenstein_matcher(1))
+    -> decltype(find<T>(std::declval<basic_value<C, M, V>&&>(), ky))
+{
+    basic_value<C, M, V> v = v_; // to re-use later, store it once
+    try
+    {
+        return std::move(find<T>(v, ky)); // pass lref, move later
+    }
+    catch(const std::out_of_range& oor)
+    {
+        auto& t = v.as_table(); // because v is used here
+        const auto found = detail::find_unique(t.begin(), t.end(), v, ky, match);
+        if(found != t.end())
+        {
+            return get<T>(std::move(found->second));
+        }
+        throw;
+    }
+}
+
+// ---------------------------------------------------------------------------
+// no-template-argument case (by default, return toml::value).
+// toml::find_fuzzy(v, "tablename", FuzzyMatcher);
+
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher = levenstein_matcher>
+basic_value<C, M, V> const&
+find_fuzzy(const basic_value<C, M, V>& v, const key& ky,
+           const FuzzyMatcher match = levenstein_matcher(1))
+{
+    try
+    {
+        return find(v, ky);
+    }
+    catch(const std::out_of_range& oor)
+    {
+        const auto& t = v.as_table();
+        const auto found = detail::find_unique(t.begin(), t.end(), v, ky, match);
+        if(found != t.end())
+        {
+            return found->second;
+        }
+        throw;
+    }
+}
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher = levenstein_matcher>
+basic_value<C, M, V>&
+find_fuzzy(basic_value<C, M, V>& v, const key& ky,
+           const FuzzyMatcher match = levenstein_matcher(1))
+{
+    try
+    {
+        return find(v, ky);
+    }
+    catch(const std::out_of_range& oor)
+    {
+        auto& t = v.as_table();
+        const auto found = detail::find_unique(t.begin(), t.end(), v, ky, match);
+        if(found != t.end())
+        {
+            return found->second;
+        }
+        throw;
+    }
+}
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher = levenstein_matcher>
+basic_value<C, M, V>&&
+find_fuzzy(basic_value<C, M, V>&& v_, const key& ky,
+           const FuzzyMatcher match = levenstein_matcher(1))
+{
+    basic_value<C, M, V> v = v_; // to re-use later, store it once
+    try
+    {
+        return std::move(find(v, ky));
+    }
+    catch(const std::out_of_range& oor)
+    {
+        auto& t = v.as_table();
+        const auto found = detail::find_unique(t.begin(), t.end(), v, ky, match);
+        if(found != t.end())
+        {
+            return std::move(found->second);
+        }
+        throw;
+    }
+}
+
+// ===========================================================================
+// find(v, k, matcher)
+//
+// when matcher is passed, check a key that matches exists or not. if it exists,
+// suggest that in the error message
+
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher>
+basic_value<C, M, V> const&
+find(const basic_value<C, M, V>& v, const key& ky, FuzzyMatcher match)
+{
+    const auto& tab = v.template cast<value_t::table>();
+    if(tab.count(ky) == 0)
+    {
+        for(const auto& kv : tab)
+        {
+            if(match(kv.first, ky))
+            {
+                throw std::out_of_range(detail::format_underline(concat_to_string(
+                    "[error] key \"", ky, "\" not found."), {
+                        {std::addressof(detail::get_region(v)), "in this table"},
+                        {std::addressof(detail::get_region(kv.second)),
+                         "did you mean this?"}
+                    }));
+            }
+        }
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return tab.at(ky);
+}
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher>
+basic_value<C, M, V>&
+find(basic_value<C, M, V>& v, const key& ky, FuzzyMatcher match)
+{
+    auto& tab = v.template cast<value_t::table>();
+    if(tab.count(ky) == 0)
+    {
+        for(const auto& kv : tab)
+        {
+            if(match(kv.first, ky))
+            {
+                throw std::out_of_range(detail::format_underline(concat_to_string(
+                    "[error] key \"", ky, "\" not found."), {
+                        {std::addressof(detail::get_region(v)), "in this table"},
+                        {std::addressof(detail::get_region(kv.second)),
+                         "did you mean this?"}
+                    }));
+            }
+        }
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return tab.at(ky);
+}
+template<typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher>
+basic_value<C, M, V>&&
+find(basic_value<C, M, V>&& v, const key& ky, FuzzyMatcher match)
+{
+    auto tab = std::move(v).as_table();
+    if(tab.count(ky) == 0)
+    {
+        for(const auto& kv : tab)
+        {
+            if(match(kv.first, ky))
+            {
+                throw std::out_of_range(detail::format_underline(concat_to_string(
+                    "[error] key \"", ky, "\" not found."), {
+                        {std::addressof(detail::get_region(v)), "in this table"},
+                        {std::addressof(detail::get_region(kv.second)),
+                         "did you mean this?"}
+                    }));
+            }
+        }
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return std::move(tab.at(ky));
+}
+
+// ----------------------------------------------------------------------------
+// find<T>(value, key, fuzzy_matcher);
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher>
+detail::enable_if_t<
+    detail::negation<std::is_convertible<FuzzyMatcher, std::string>>::value,
+    decltype(::toml::get<T>(std::declval<basic_value<C, M, V> const&>()))>
+find(const basic_value<C, M, V>& v, const key& ky, FuzzyMatcher match)
+{
+    const auto& tab = v.as_table();
+    if(tab.count(ky) == 0)
+    {
+        for(const auto& kv : tab)
+        {
+            if(match(kv.first, ky))
+            {
+                throw std::out_of_range(detail::format_underline(concat_to_string(
+                    "[error] key \"", ky, "\" not found."), {
+                        {std::addressof(detail::get_region(v)), "in this table"},
+                        {std::addressof(detail::get_region(kv.second)),
+                         "did you mean this here?"}
+                    }));
+            }
+        }
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return ::toml::get<T>(tab.at(ky));
+}
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher>
+detail::enable_if_t<
+    detail::negation<std::is_convertible<FuzzyMatcher, std::string>>::value,
+    decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&>()))>
+find(basic_value<C, M, V>& v, const key& ky, FuzzyMatcher match)
+{
+    auto& tab = v.as_table();
+    if(tab.count(ky) == 0)
+    {
+        for(const auto& kv : tab)
+        {
+            if(match(kv.first, ky))
+            {
+                throw std::out_of_range(detail::format_underline(concat_to_string(
+                    "[error] key \"", ky, "\" not found."), {
+                        {std::addressof(detail::get_region(v)), "in this table"},
+                        {std::addressof(detail::get_region(kv.second)),
+                         "did you mean this here?"}
+                    }));
+            }
+        }
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return ::toml::get<T>(tab.at(ky));
+}
+
+template<typename T, typename C,
+         template<typename ...> class M, template<typename ...> class V,
+         typename FuzzyMatcher>
+detail::enable_if_t<
+    detail::negation<std::is_convertible<FuzzyMatcher, std::string>>::value,
+    decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&&>()))>
+find(basic_value<C, M, V>&& v, const key& ky, FuzzyMatcher match)
+{
+    auto tab = v.as_table();
+    if(tab.count(ky) == 0)
+    {
+        for(const auto& kv : tab)
+        {
+            if(match(kv.first, ky))
+            {
+                throw std::out_of_range(detail::format_underline(concat_to_string(
+                    "[error] key \"", ky, "\" not found."), {
+                        {std::addressof(detail::get_region(v)), "in this table"},
+                        {std::addressof(detail::get_region(kv.second)),
+                         "did you mean this here?"}
+                    }));
+            }
+        }
+        throw std::out_of_range(detail::format_underline(concat_to_string(
+            "[error] key \"", ky, "\" not found"), {
+                {std::addressof(detail::get_region(v)), "in this table"}
+            }));
+    }
+    return ::toml::get<T>(std::move(tab.at(ky)));
+}
+
+} // toml
+#endif// TOML11_FIND_HPP

toml/get.hpp

@@ -420,158 +420,6 @@ T get(const basic_value<C, M, V>& v)
     return ::toml::from<T>::from_toml(v);
 }
 
-// ============================================================================
-// find and get
-
-// ----------------------------------------------------------------------------
-// these overloads do not require to set T. and returns value itself.
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V> const& find(const basic_value<C, M, V>& v, const key& ky)
-{
-    const auto& tab = v.template cast<value_t::table>();
-    if(tab.count(ky) == 0)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "[error] key \"", ky, "\" not found"), {
-                {std::addressof(detail::get_region(v)), "in this table"}
-            }));
-    }
-    return tab.at(ky);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>& find(basic_value<C, M, V>& v, const key& ky)
-{
-    auto& tab = v.template cast<value_t::table>();
-    if(tab.count(ky) == 0)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "[error] key \"", ky, "\" not found"), {
-                {std::addressof(detail::get_region(v)), "in this table"}
-            }));
-    }
-    return tab.at(ky);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>&& find(basic_value<C, M, V>&& v, const key& ky)
-{
-    auto& tab = v.template cast<value_t::table>();
-    if(tab.count(ky) == 0)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "[error] key \"", ky, "\" not found"), {
-                {std::addressof(detail::get_region(v)), "in this table"}
-            }));
-    }
-    return std::move(tab.at(ky));
-}
-
-// ----------------------------------------------------------------------------
-// find<T>(value, key);
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V> const&>()))
-find(const basic_value<C, M, V>& v, const key& ky)
-{
-    const auto& tab = v.template cast<value_t::table>();
-    if(tab.count(ky) == 0)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "[error] key \"", ky, "\" not found"), {
-                {std::addressof(detail::get_region(v)), "in this table"}
-            }));
-    }
-    return ::toml::get<T>(tab.at(ky));
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&>()))
-find(basic_value<C, M, V>& v, const key& ky)
-{
-    auto& tab = v.template cast<value_t::table>();
-    if(tab.count(ky) == 0)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "[error] key \"", ky, "\" not found"), {
-                {std::addressof(detail::get_region(v)), "in this table"}
-            }));
-    }
-    return ::toml::get<T>(tab.at(ky));
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&&>()))
-find(basic_value<C, M, V>&& v, const key& ky)
-{
-    auto& tab = v.template cast<value_t::table>();
-    if(tab.count(ky) == 0)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "[error] key \"", ky, "\" not found"), {
-                {std::addressof(detail::get_region(v)), "in this table"}
-            }));
-    }
-    return ::toml::get<T>(std::move(tab.at(ky)));
-}
-
-// --------------------------------------------------------------------------
-// toml::find(toml::value, toml::key, Ts&& ... keys)
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename ... Ts>
-const basic_value<C, M, V>&
-find(const basic_value<C, M, V>& v, const ::toml::key& ky, Ts&& ... keys)
-{
-    return ::toml::find(::toml::find(v, ky), std::forward<Ts>(keys)...);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename ... Ts>
-basic_value<C, M, V>&
-find(basic_value<C, M, V>& v, const ::toml::key& ky, Ts&& ... keys)
-{
-    return ::toml::find(::toml::find(v, ky), std::forward<Ts>(keys)...);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename ... Ts>
-basic_value<C, M, V>&&
-find(basic_value<C, M, V>&& v, const ::toml::key& ky, Ts&& ... keys)
-{
-    return ::toml::find(::toml::find(std::move(v), ky), std::forward<Ts>(keys)...);
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename ... Ts>
-decltype(::toml::get<T>(std::declval<const basic_value<C, M, V>&>()))
-find(const basic_value<C, M, V>& v, const ::toml::key& ky, Ts&& ... keys)
-{
-    return ::toml::find<T>(::toml::find(v, ky), std::forward<Ts>(keys)...);
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename ... Ts>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&>()))
-find(basic_value<C, M, V>& v, const ::toml::key& ky, Ts&& ... keys)
-{
-    return ::toml::find<T>(::toml::find(v, ky), std::forward<Ts>(keys)...);
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename ... Ts>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&&>()))
-find(basic_value<C, M, V>&& v, const ::toml::key& ky, Ts&& ... keys)
-{
-    return ::toml::find<T>(::toml::find(std::move(v), ky), std::forward<Ts>(keys)...);
-}
-
 // ============================================================================
 // get_or(value, fallback)
 
@@ -745,199 +593,5 @@ get_or(const basic_value<C, M, V>& v, T&& opt)
     }
 }
 
-// ===========================================================================
-// find_or(value, key, fallback)
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V> const&
-find_or(const basic_value<C, M, V>& v, const key& ky,
-        const basic_value<C, M, V>& opt)
-{
-    if(!v.is_table()) {return opt;}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return tab.at(ky);
-}
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>&
-find_or(basic_value<C, M, V>& v, const toml::key& ky, basic_value<C, M, V>& opt)
-{
-    if(!v.is_table()) {return opt;}
-    auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return tab[ky];
-}
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>
-find_or(basic_value<C, M, V>&& v, const toml::key& ky, basic_value<C, M, V>&& opt)
-{
-    if(!v.is_table()) {return opt;}
-    auto tab = std::move(v).as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return std::move(tab[ky]);
-}
-
-// ---------------------------------------------------------------------------
-// exact types (return type can be a reference)
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T> const&
-find_or(const basic_value<C, M, V>& v, const key& ky, const T& opt)
-{
-    if(!v.is_table()) {return opt;}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return get_or(tab.at(ky), opt);
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T>&
-find_or(basic_value<C, M, V>& v, const toml::key& ky, T& opt)
-{
-    if(!v.is_table()) {return opt;}
-    auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return get_or(tab[ky], opt);
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T>&&
-find_or(basic_value<C, M, V>&& v, const toml::key& ky, T&& opt)
-{
-    if(!v.is_table()) {return opt;}
-    auto tab = std::move(v).as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return get_or(std::move(tab[ky]), std::forward<T>(opt));
-}
-
-// ---------------------------------------------------------------------------
-// std::string (return type can be a reference)
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<std::is_same<T, std::string>::value, std::string> const&
-find_or(const basic_value<C, M, V>& v, const key& ky, const T& opt)
-{
-    if(!v.is_table()) {return opt;}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return get_or(tab.at(ky), opt);
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<std::is_same<T, std::string>::value, std::string>&
-find_or(basic_value<C, M, V>& v, const toml::key& ky, T& opt)
-{
-    if(!v.is_table()) {return opt;}
-    auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return get_or(tab.at(ky), opt);
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<std::is_same<T, std::string>::value, std::string>
-find_or(basic_value<C, M, V>&& v, const toml::key& ky, T&& opt)
-{
-    if(!v.is_table()) {return std::forward<T>(opt);}
-    auto tab = std::move(v).as_table();
-    if(tab.count(ky) == 0) {return std::forward<T>(opt);}
-    return get_or(std::move(tab.at(ky)), std::forward<T>(opt));
-}
-
-// ---------------------------------------------------------------------------
-// string literal (deduced as std::string)
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_string_literal<typename std::remove_reference<T>::type>::value,
-    std::string>
-find_or(const basic_value<C, M, V>& v, const toml::key& ky, T&& opt)
-{
-    if(!v.is_table()) {return std::string(opt);}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return std::string(opt);}
-    return get_or(tab.at(ky), std::forward<T>(opt));
-}
-
-// ---------------------------------------------------------------------------
-// others (require type conversion and return type cannot be lvalue reference)
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    // T is not an exact toml type
-    detail::negation<detail::is_exact_toml_type<
-        typename std::remove_cv<typename std::remove_reference<T>::type>::type,
-        basic_value<C, M, V>>>,
-    // T is not std::string
-    detail::negation<std::is_same<std::string,
-        typename std::remove_cv<typename std::remove_reference<T>::type>::type>>,
-    // T is not a string literal
-    detail::negation<detail::is_string_literal<
-        typename std::remove_reference<T>::type>>
-    >::value, typename std::remove_cv<typename std::remove_reference<T>::type>::type>
-find_or(const basic_value<C, M, V>& v, const toml::key& ky, T&& opt)
-{
-    if(!v.is_table()) {return std::forward<T>(opt);}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return std::forward<T>(opt);}
-    return get_or(tab.at(ky), std::forward<T>(opt));
-}
-
-// ============================================================================
-// expect
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-result<T, std::string> expect(const basic_value<C, M, V>& v) noexcept
-{
-    try
-    {
-        return ok(get<T>(v));
-    }
-    catch(const std::exception& e)
-    {
-        return err(e.what());
-    }
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-result<T, std::string>
-expect(const basic_value<C, M, V>& v, const toml::key& k) noexcept
-{
-    try
-    {
-        return ok(find<T>(v, k));
-    }
-    catch(const std::exception& e)
-    {
-        return err(e.what());
-    }
-}
-template<typename T, typename Table>
-detail::enable_if_t<detail::conjunction<
-    detail::is_map<Table>, detail::is_basic_value<typename Table::mapped_type>
-    >::value, result<T, std::string>>
-expect(const Table& t, const toml::key& k,
-       std::string tablename = "unknown table") noexcept
-{
-    try
-    {
-        return ok(find<T>(t, k, std::move(tablename)));
-    }
-    catch(const std::exception& e)
-    {
-        return err(e.what());
-    }
-}
 } // toml
 #endif// TOML11_GET