feat: add examples

examples/unicode/.gitignore

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+canonicalize

examples/unicode/CMakeLists.txt

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+include(FetchContent)
+
+FetchContent_Declare(uni-algo
+  GIT_REPOSITORY https://github.com/uni-algo/uni-algo.git
+  GIT_SHALLOW ON  # Download the branch without its history
+  GIT_TAG v1.0.0) # The version you want to download
+
+# Be aware that FetchContent_MakeAvailable requires CMake 3.14 or higher
+FetchContent_MakeAvailable(uni-algo)
+
+add_executable(canonicalize canonicalize.cpp)
+target_link_libraries(canonicalize PRIVATE toml11::toml11 uni-algo::uni-algo)
+set_target_properties(canonicalize PROPERTIES
+    RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
+

examples/unicode/README.md

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+# reflect
+
+Compare TOML key after NFC canonicalization.
+
+It depends on [uni-algo](https://github.com/uni-algo/uni-algo.git).
+
+The example contains two keys that are different in bytewise comparison, but becomes the same after NFC normalization.
+
+## build
+
+Build toml11 with `-DTOML11_BUILD_EXAMPLES=ON`.
+
+```cpp
+$ cmake -B ./build/ -DTOML11_BUILD_EXAMPLES=ON
+```

examples/unicode/canonicalize.cpp

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+#include <toml.hpp>
+#include <uni_algo/norm.h>
+
+#include <iostream>
+#include <map>
+
+struct nfc_comparator
+{
+    using first_argument_type  = std::string;
+    using second_argument_type = std::string;
+    using result_type          = bool;
+
+    result_type operator()(const first_argument_type& lhs, const second_argument_type& rhs) const
+    {
+        return una::norm::to_nfc_utf8(lhs) < una::norm::to_nfc_utf8(rhs);
+    }
+};
+
+struct nfc_equal_to
+{
+    using first_argument_type  = std::string;
+    using second_argument_type = std::string;
+    using result_type          = bool;
+
+    result_type operator()(const first_argument_type& lhs, const second_argument_type& rhs) const
+    {
+        return una::norm::to_nfc_utf8(lhs) == una::norm::to_nfc_utf8(rhs);
+    }
+};
+
+struct nfc_hasher
+{
+    std::size_t operator()(const std::string& s) const
+    {
+        return std::hash<std::string>{}(una::norm::to_nfc_utf8(s));
+    }
+};
+
+struct nfc_config
+{
+    using comment_type  = toml::preserve_comments;
+
+    using boolean_type  = bool;
+    using integer_type  = std::int64_t;
+    using floating_type = double;
+    using string_type   = std::string;
+
+    template<typename T>
+    using array_type = std::vector<T>;
+    template<typename K, typename T>
+    // using table_type = std::map<K, T, nfc_comparator>;
+    using table_type = std::unordered_map<K, T, nfc_hasher, nfc_equal_to>;
+
+    static toml::result<integer_type, toml::error_info>
+    parse_int(const std::string& str, const toml::source_location src, const std::uint8_t base)
+    {
+        return toml::read_int<integer_type>(str, src, base);
+    }
+    static toml::result<floating_type, toml::error_info>
+    parse_float(const std::string& str, const toml::source_location src, const bool is_hex)
+    {
+        return toml::read_float<floating_type>(str, src, is_hex);
+    }
+};
+
+
+int main(int argc, char **argv)
+{
+    if(argc != 2)
+    {
+        return 1;
+    }
+
+    const auto input = toml::parse<nfc_config>(argv[1]);
+
+    std::cout << toml::format(input) << std::endl;
+
+    return 0;
+}

examples/unicode/input.toml

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+"W\u0302" = 1 # in NFC, this key is the same as the following key
+"Ŵ"       = 2 # so it fails.