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432 lines
16 KiB
Markdown
432 lines
16 KiB
Markdown
toml11
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======
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[](https://travis-ci.org/ToruNiina/toml11)
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[](https://ci.appveyor.com/project/ToruNiina/toml11)
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[](LICENSE)
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[](https://doi.org/10.5281/zenodo.1209136)
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c++11 header-only toml parser depending only on c++ standard library.
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compatible to the latest version of TOML v0.5.0 after version 2.0.0.
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Are you looking for pre-C++11 compatible toml parser? Check out [Boost.toml](https://github.com/ToruNiina/Boost.toml)! It has almost the same functionality as this library and work with C++98 & Boost.
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## How to use
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### installation
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Just include the file after adding correct include path.
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```cpp
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#include <toml11/toml.hpp> // that's all! now you can use it.
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int main()
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{
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const auto data = toml::parse("example.toml");
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const auto title = toml::get<std::string>(data.at("title"));
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std::cout << "the title is " << title << std::endl;
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}
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```
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## decoding toml file
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### parsing toml file
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The only thing you have to do is passing a filename to `toml::parse` function.
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```cpp
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const std::string fname("sample.toml");
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const toml::table data = toml::parse(fname);
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```
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In the case of file open error, it will throw `std::runtime_error`.
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You can pass also `stream` to `toml::parse` function after checking the status.
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```cpp
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std::ifstream ifs("sample.toml");
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assert(ifs.good());
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const auto data = toml::parse(ifs /*, "filename" (optional)*/);
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```
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To show a better error message, it is recommended to pass filename with `istream`. See also [in the case of syntax error](#in-the-case-of-syntax-error) and [passing invalid type to toml::get](#passing-invalid-type-to-tomlget).
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### in the case of syntax error
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If there is a syntax error in a toml file, `toml::parse` will throw `toml::syntax_error`.
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toml11 now has clean error messages inspired the Rust compiler and it looks like the following.
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```console
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terminate called after throwing an instance of 'toml::syntax_error'
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what(): [error] toml::parse_table: invalid line format # error description
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--> example.toml # file name (and path, if any)
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3 | a = 42 = true # line num and content
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| ^------ expected newline, but got '='. # error reason
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```
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It shows almost all the information to fix the error in the toml file like file name, line number, the line that is invalid, and the reason why it fails.
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Since the error message generation is generally a difficult task, the current status is not ideal. We need your help. If you encounter a weird error message, please let us know and improve the quality!
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### getting toml value
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After parsing successfully, you can obtain the values from the result of `toml::parse` (here, `data`) using `toml::get` function.
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```toml
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answer = 42
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pi = 3.14
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numbers = [1,2,3]
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time = 1979-05-27T07:32:00Z
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[tab]
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key = "value"
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```
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``` cpp
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const auto answer = toml::get<std::int64_t >(data.at("answer"));
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const auto pi = toml::get<double >(data.at("pi"));
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const auto numbers = toml::get<std::vector<int>>(data.at("numbers"));
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const auto timepoint = toml::get<std::chrono::system_clock::time_point>(data.at("time"));
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const auto tab = toml::get<toml::Table>(data.at("tab"));
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const auto key = toml::get<std::string>( tab.at("key"));
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```
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When you pass an exact TOML type that does not require type conversion, `toml::get` returns also a reference through which you can modify the content.
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```cpp
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toml::get<toml::integer>(data["answer"]) = 6 * 9;
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std::cout << toml::get<int>(data.at("answer")) << std::endl; // 54
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```
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#### passing invalid type to toml::get
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If you choose the invalid type, `toml::type_error` will be thrown. Similar to the `syntax_error`, toml11 also displays informative error message. The error message when you choose `int` to get `string` value would be like this.
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```console
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terminate called after throwing an instance of 'toml::type_error'
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what(): [error] toml::value bad_cast to integer
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--> example.toml
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3 | title = "TOML Example"
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| ~~~~~~~~~~~~~~ the actual type is string
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```
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NOTE: In order to show this kind of error message, all the toml values has 1 shared_ptr that points the corresponding byte sequence and 2 iterator that points the range. It is recommended to destruct all the `toml::value` classes after configuring your application to save the memory resource.
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#### finding value from table
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toml11 provides overloads to find a value from `toml::table`. Of course, you can do this in your own way with `toml::get` because it just searches and returns a value.
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```cpp
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const auto data = toml::parse("example.toml");
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const auto num = toml::get<int>(data, "num", /*optional*/"example.toml");
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```
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If the value does not exists, it throws `std::out_of_range` with informative error message.
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```console
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terminate called after throwing an instance of 'std::out_of_range'
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what(): [error] key "num" not found in example.toml
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```
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You can use this with a `toml::value` that is expected to be a `toml::table`. It automatically casts the value to table.
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```cpp
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const auto data = toml::parse("example.toml");
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const auto num = toml::get<int>(data.at("table"), "num");
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// expecting the following example.toml
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// [table]
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// num = 42
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```
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In this case, because the value `data.at("table")` knows the locatoin of itself, you don't need to pass where you find the value. `toml::get` will show you a great error message.
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```console
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terminate called after throwing an instance of 'std::out_of_range'
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what(): [error] key "num" not found
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--> example.toml
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3 | [table]
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| ~~~~~~~ in this table
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```
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If it's not a `toml::table`, error like "invalid type" would be thrown.
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### getting arrays
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You can set any kind of `container` class to obtain `toml::array` except for `map`-like classes.
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``` cpp
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const auto vc = toml::get<std::vector<int> >(data.at("numbers"));
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const auto ls = toml::get<std::list<int> >(data.at("numbers"));
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const auto dq = toml::get<std::deque<int> >(data.at("numbers"));
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const auto ar = toml::get<std::array<int, 3>>(data.at("numbers"));
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// if the size of data.at("numbers") is larger than that of std::array,
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// it will throw toml::type_error because std::array is not resizable.
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```
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Surprisingly, you can get `toml::array` as `std::pair` and `std::tuple.`
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```cpp
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const auto tp = toml::get<std::tuple<short, int, unsigned int>>(data.at("numbers"));
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```
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The case when you need this functionality is to get an array of arrays.
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```toml
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aofa = [[1,2,3], ["foo", "bar", "baz"]] # toml allows this
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```
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What is the corresponding C++ type? Obviously, it is a `std::pair` of `std::vector`s.
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```cpp
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const auto aofa = toml::get<
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std::pair<std::vector<int>, std::vector<std::string>>
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>(data.at("aofa"));
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```
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If you don't know what the type is inside the array, you can use `toml::array` which is a `std::vector` of `toml::value`instead.
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```cpp
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const auto aofa = toml::get<toml::array>(data.at("aofa"));
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const auto first = toml::get<toml::array>(aofa.at(0));
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```
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See also [expecting conversion](#expecting-conversion) and [checking-value-type](#checking-value-type).
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### getting tables
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`toml::table` is a key component of this library, that is an alias of a `std::unordered_map` from `toml::key (a.k.a. std::string)` to `toml::value`. `toml::parse` returns this as a result.
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Since it is just an alias of `std::unordered_map`, it has all the functionalities that `std::unordered_map` has, e.g. `operator[]`, `count`, and `find`.
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```cpp
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toml::table data = toml::parse("example.toml");
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if(data.count("title") != 0)
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{
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data["title"] = std::string("TOML example");
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}
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```
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For the case that all the values of the table have the same type, toml11 allows you to convert `toml::table` to `map`s that contains the convertible type.
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```toml
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[tab]
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key1 = "foo" # all the values are
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key2 = "bar" # toml String
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```
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```cpp
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const auto tab = toml::get<std::map<std::string, std::string>>(data.at("tab"));
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std::cout << tab["key1"] << std::endl; // foo
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std::cout << tab["key2"] << std::endl; // bar
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```
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### dotted keys
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TOML v0.5.0 has a new feature named "dotted keys". You can chain keys to represent the structure of the data.
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```toml
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physical.color = "orange"
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physical.shape = "round"
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```
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This is equivalent to the following.
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```toml
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[physical]
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color = "orange"
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shape = "round"
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```
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You can get both of the above formats with the same c++ code.
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```cpp
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const auto physical = toml::get<toml::table>(data.at("physical"));
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const auto color = toml::get<std::string>(physical.at("color"));
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```
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### an array of tables
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An array of tables is just an array of tables. You can get completely in the same way as the other arrays and tables.
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```toml
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array_of_inline_table = [{key = "value1"}, {key = "value2"}, {key = "value3"}]
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[[array_of_table]]
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key = "value4"
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[[array_of_table]]
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key = "value5"
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[[array_of_table]]
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key = "value6"
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```
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```cpp
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const auto aot1 = toml::get<std::vector<toml::table>>(data.at("array_of_inline_table"));
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const auto aot2 = toml::get<std::vector<toml::table>>(data.at("array_of_table"));
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```
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### cost of conversion
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Although `toml::get` is convenient, it has additional copy-cost because it copies data contained in `toml::value` to user-specified type. Of course in some case this overhead is not ignorable.
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By passing the exact types, `toml::get` returns reference that has nealy zero overhead.
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``` cpp
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const auto& tab = toml::get<toml::array>(data.at("tab"));
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const auto& numbers = toml::get<toml::table>(data.at("numbers"));
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```
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Unfortunately, in this case you need to call `toml::get` each time you access to the element of `toml::array` because `toml::array` is an array of `toml::value`.
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```cpp
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const auto& num0 = toml::get<toml::integer>(numbers.at(0));
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const auto& num1 = toml::get<toml::integer>(numbers.at(1));
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const auto& num2 = toml::get<toml::integer>(numbers.at(2));
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```
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### datetime and its variants
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TOML v0.5.0 has 4 different datetime objects, `local_date`, `local_time`, `local_datetime`, and `offset_datetime`. With toml11, you can convert `local_time` to your favorite `std::chrono::duration` and others to `std::chrono::system_clock::time_point`.
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```toml
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time = 12:30:00
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date = 2018-12-23
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```
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```cpp
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const auto dur = toml::get<std::chrono::minutes>(data.at("time")); // 12 * 60 + 30 min
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const auto tp = toml::get<std::chrono::system_clock::time_point>(data.at("date"));
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```
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### getting with a fallback
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`toml::get_or` returns a default value if `toml::get<T>` failed.
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```cpp
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toml::table data; // empty table!
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const auto value = toml::get_or(data, "key", 42); // value => int 42.
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```
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`toml::get_or` automatically deduces what type you want to get from the default value you passed.
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### expecting conversion
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By using `toml::expect`, you will get your expected value or an error message without throwing `toml::type_error`.
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```cpp
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const auto value = toml::expect<std::string>(data.at("title"));
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if(value.is_ok()) {
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std::cout << value.unwrap() << std::endl;
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} else {
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std::cout << value.unwrap_err() << std::endl;
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}
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```
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Also, you can pass a function object to modify the expected value.
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```cpp
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const auto value = toml::expect<int>(data.at("number"))
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.map(// function that receives expected type (here, int)
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[](const int number) -> double {
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return number * 1.5 + 1.0;
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}).unwrap_or(/*default value =*/ 3.14);
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```
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### checking value type
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When you don't know the exact type of toml-value, you can get `enum` type from `toml::value`.
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```cpp
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switch(data.at("something").type())
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{
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case toml::value_t::Integer: /* do some stuff */; break;
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case toml::value_t::Float : /* do some stuff */; break;
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case toml::value_t::String : /* do some stuff */; break;
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default : throw std::runtime_error(
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"unexpected type : " + toml::stringize(data.at("something").type()));
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}
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```
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### fill only the matched value
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The more sophisticated way is using `toml::from_toml` and `std::tie`.
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```cpp
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toml::table data{{"something", toml::value("foo")}};
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int i = 0;
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double d = 0.;
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std::string s;
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toml::from_toml(std::tie(i, d, s), data.at("something"));
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std::cout << i << ", " << d << ", " << s << std::endl; // 0, 0, foo
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```
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Here, only matched value will be filled. The others are left intact after calling `from_toml`.
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It should be noted that `toml::from_toml` returns as usual even if there are no matched type.
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`from_toml` can be used also for single type.
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```cpp
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int i = 0;
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toml::from_toml(i, data.at("something"));
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```
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### sanitizing UTF-8 codepoints
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toml11 shows warning if a value of an escape sequence to represent unicode character exceeds the range of unicode.
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```console
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[warning] input codepoint (0011FFFF) is too large to decode as a unicode character. The result may not be able to render to your screen.
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--> example.toml
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3 | exceeds_unicode = "\U0011FFFF example"
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| ~~~~~~~~~ should be in [0x00..0x10FFFF]
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```
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Also, toml11 throws `std::domain_error` if the code point exceeds the range that can be represented by utf-8.
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```console
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terminate called after throwing an instance of 'std::range_error'
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what(): [error] input codepoint (0020FFFF) is too large to encode as utf-8.
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--> example.toml
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3 | exceeds_utf8 = "\U0020FFFF example"
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| ~~~~~~~~~ should be in [0x00..0x10FFFF]
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```
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## underlying types
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The toml types (can be used as `toml::*` in this library) and corresponding `enum` name are listed in the table below.
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| toml::type | underlying c++ type | enum |
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| -------------- | -------------------------------------------- | ------------------------------- |
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| Boolean | `bool` | `toml::value_t::Boolean` |
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| Integer | `std::int64_t` | `toml::value_t::Integer` |
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| Float | `double` | `toml::value_t::Float` |
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| String | `toml::string` | `toml::value_t::String` |
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| LocalDate | `toml::local_date` | `toml::value_t::LocalDate` |
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| LocalTime | `toml::local_time` | `toml::value_t::LocalTime` |
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| LocalDatetime | `toml::local_datetime` | `toml::value_t::LocalDatetime` |
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| OffsetDatetime | `toml::offset_datetime` | `toml::value_t::offsetDatetime` |
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| Array | `std::vector<toml::value>` | `toml::value_t::Array` |
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| Table | `std::unordered_map<std::string, toml::key>` | `toml::value_t::Table` |
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`toml::string` is effectively the same as `std::string` but has an additional flag that represents a kind of a string, `string_t::basic` and `string_t::literal`. Although `std::string` is not an exact toml type, but still you can get a reference that points internal `std::string` by using `toml::get<std::string>()` for the convenience.
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`Datetime` variants are `struct` that are defined in this library. Because `std::chrono::system_clock::time_point` is a __time point__, not capable of representing a Local Time independent from a specific day.
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It is recommended to get `Datetime`s as `std::chrono` classes through `toml::get`.
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## Contributors
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I thank the contributor for providing great feature to this repository.
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- Guillaume Fraux (@Luthaf)
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- Windows support and CI on Appvayor
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- Intel Compiler support
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## Licensing terms
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This product is licensed under the terms of the [MIT License](LICENSE).
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- Copyright (c) 2017 Toru Niina
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All rights reserved.
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