<commit_before># JSON for Modern C++

*What if JSON was part of modern C++?*

[![Build Status](https://travis-ci.org/nlohmann/json.png?branch=master)](https://travis-ci.org/nlohmann/json)
[![Coverage Status](https://img.shields.io/coveralls/nlohmann/json.svg)](https://coveralls.io/r/nlohmann/json)
[![Github Issues](https://img.shields.io/github/issues/nlohmann/json.svg)](http://github.com/nlohmann/json/issues)

## Design goals

There are myriads of [JSON](http://json.org) libraries out there, and each may even have its reason to exist. Our class had these design goals:

- **Intuitive syntax**. In languages such as Python, JSON feels like a first class data type. We used all the operator magic of modern C++ to achieve the same feeling in your code. Check out the [examples below](#examples) and you know, what I mean.

- **Trivial integration**. Our whole code consists of a single header file `json.hpp`. That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.

- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/blob/master/test/json_unit.cc) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](http://valgrind.org) that there are no memory leaks.

Other aspects were not so important to us:

- **Memory efficiency**. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). The default generalization uses the following C++ data types: `std::string` for strings, `int64_t` or `double` for numbers, `std::map` for objects, `std::vector` for arrays, and `bool` for Booleans. However, you can template the generalized class `basic_json` to your needs.

- **Speed**. We currently implement the parser as naive [recursive descent parser](http://en.wikipedia.org/wiki/Recursive_descent_parser) with hand coded string handling. It is fast enough, but a [LALR-parser](http://en.wikipedia.org/wiki/LALR_parser) with a decent regular expression processor should be even faster (but would consist of more files which makes the integration harder).

- **Rigorous Unicode compliance**. We did our best to implement some robust Unicode support. There are still some issues with escaping, and if you run into a problem, please [tell me](https://github.com/nlohmann/json/issues).

## Updates since last version

As of February 2015, the following updates were made to the library

- *Changed:* In the generic class `basic_json`, all JSON value types (array, object, string, bool, integer number, and floating-point) are now **templated**. That is, you can choose whether you like a `std::list` for your arrays or an `std::unordered_map` for your objects. The specialization `json` sets some reasonable defaults.
- *Changed:* The library now consists of a single header, called `json.hpp`. Consequently, build systems such as Automake or CMake are not any longer required.
- *Changed:* The **deserialization** is now supported by a lexer generated with [re2c](http://re2c.org) from file [`src/json.hpp.re2c`](https://github.com/nlohmann/json/blob/master/src/json.hpp.re2c). As a result, we follow the JSON specification more strictly. Note neither the tool re2c nor its input are required to use the class.
- *Added:* The library now satisfies the [**ReversibleContainer**](http://en.cppreference.com/w/cpp/concept/ReversibleContainer) requirement. It hence provides four different iterators (`iterator`, `const_iterator`, `reverse_iterator`, and `const_reverse_iterator`), comparison functions, `swap()`, `size()`, `max_size()`, and `empty()` member functions.
- *Added*: The class uses **user-defined allocators** which default to `std::allocator`, but can be templated via parameter `Allocator`.
- *Added:* To simplify pretty-printing, the `std::setw` **stream manipulator** has been overloaded to set the desired indentation. Pretty-printing a JSON object `j` is as simple as `std::cout << std::setw(4) << j << '\n'.
- *Changed*: The type `json::value_t::number` is now called `json::value_t::number_integer` to be more symmetric compared to `json::value_t::number_float`.
- *Removed:* The `key()` and `value()` member functions for object iterators were nonstandard and yielded more problems than benefits. They were removed from the library.

## Integration

The single required source, `json.hpp` file is in the `src` directory. All you need to do is add

```cpp
#include "json.hpp"

// for convenience
using json = nlohmann::json;
```

to the files you want to use JSON objects. That's it. Do not forget to set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and Clang).

## Examples<commit_msg>minor syntax error in README<commit_after># JSON for Modern C++

*What if JSON was part of modern C++?*

[![Build Status](https://travis-ci.org/nlohmann/json.png?branch=master)](https://travis-ci.org/nlohmann/json)
[![Coverage Status](https://img.shields.io/coveralls/nlohmann/json.svg)](https://coveralls.io/r/nlohmann/json)
[![Github Issues](https://img.shields.io/github/issues/nlohmann/json.svg)](http://github.com/nlohmann/json/issues)

## Design goals

There are myriads of [JSON](http://json.org) libraries out there, and each may even have its reason to exist. Our class had these design goals:

- **Intuitive syntax**. In languages such as Python, JSON feels like a first class data type. We used all the operator magic of modern C++ to achieve the same feeling in your code. Check out the [examples below](#examples) and you know, what I mean.

- **Trivial integration**. Our whole code consists of a single header file `json.hpp`. That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.

- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/blob/master/test/json_unit.cc) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](http://valgrind.org) that there are no memory leaks.

Other aspects were not so important to us:

- **Memory efficiency**. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). The default generalization uses the following C++ data types: `std::string` for strings, `int64_t` or `double` for numbers, `std::map` for objects, `std::vector` for arrays, and `bool` for Booleans. However, you can template the generalized class `basic_json` to your needs.

- **Speed**. We currently implement the parser as naive [recursive descent parser](http://en.wikipedia.org/wiki/Recursive_descent_parser) with hand coded string handling. It is fast enough, but a [LALR-parser](http://en.wikipedia.org/wiki/LALR_parser) with a decent regular expression processor should be even faster (but would consist of more files which makes the integration harder).

- **Rigorous Unicode compliance**. We did our best to implement some robust Unicode support. There are still some issues with escaping, and if you run into a problem, please [tell me](https://github.com/nlohmann/json/issues).

## Updates since last version

As of February 2015, the following updates were made to the library

- *Changed:* In the generic class `basic_json`, all JSON value types (array, object, string, bool, integer number, and floating-point) are now **templated**. That is, you can choose whether you like a `std::list` for your arrays or an `std::unordered_map` for your objects. The specialization `json` sets some reasonable defaults.
- *Changed:* The library now consists of a single header, called `json.hpp`. Consequently, build systems such as Automake or CMake are not any longer required.
- *Changed:* The **deserialization** is now supported by a lexer generated with [re2c](http://re2c.org) from file [`src/json.hpp.re2c`](https://github.com/nlohmann/json/blob/master/src/json.hpp.re2c). As a result, we follow the JSON specification more strictly. Note neither the tool re2c nor its input are required to use the class.
- *Added:* The library now satisfies the [**ReversibleContainer**](http://en.cppreference.com/w/cpp/concept/ReversibleContainer) requirement. It hence provides four different iterators (`iterator`, `const_iterator`, `reverse_iterator`, and `const_reverse_iterator`), comparison functions, `swap()`, `size()`, `max_size()`, and `empty()` member functions.
- *Added*: The class uses **user-defined allocators** which default to `std::allocator`, but can be templated via parameter `Allocator`.
- *Added:* To simplify pretty-printing, the `std::setw` **stream manipulator** has been overloaded to set the desired indentation. Pretty-printing a JSON object `j` is as simple as `std::cout << std::setw(4) << j << '\n'`.
- *Changed*: The type `json::value_t::number` is now called `json::value_t::number_integer` to be more symmetric compared to `json::value_t::number_float`.
- *Removed:* The `key()` and `value()` member functions for object iterators were nonstandard and yielded more problems than benefits. They were removed from the library.

## Integration

The single required source, `json.hpp` file is in the `src` directory. All you need to do is add

```cpp
#include "json.hpp"

// for convenience
using json = nlohmann::json;
```

to the files you want to use JSON objects. That's it. Do not forget to set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and Clang).

## Examples
{'fraction_non_alphanumeric': 0.11515586546349467, 'fraction_numerical': 0.004511894995898278, 'mean_word_length': 4.90732889158086, 'pattern_counts': {'":': 0, '<': 15, '<?xml version=': 0, '>': 3, 'https://': 18, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '1806879', 'n_tokens_mistral': 2796, 'n_tokens_neox': 2668, 'n_words': 1201}