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38 lines
3 KiB
Markdown
38 lines
3 KiB
Markdown
# Reference
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## Types and default values
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| JSON type | value_type | C++ type | type alias | default value |
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| ----------------------- | -------------------------- | ----------------------------- | ---------------------- | --------------
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| null | `value_type::null` | `nullptr_t` | - | `nullptr` |
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| string | `value_type::string` | `std::string` | `JSON::string_t` | `""` |
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| number (integer) | `value_type::number` | `int` | `JSON::number_t` | `0` |
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| number (floating point) | `value_type::number_float` | `double` | `JSON::number_float_t` | `0.0` |
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| array | `value_type::array ` | `std::array<JSON>` | `JSON::array_t` | `{}` |
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| object | `value_type::object` | `std::map<std::string, JSON>` | `JSON::object_t` | `{}` |
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## Type conversions
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There are only a few type conversions possible:
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- An integer number can be translated to a floating point number.
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- A floating point number can be translated to an integer number. Note the number is truncated and not rounded, ceiled or floored.
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- Any value (i.e., boolean, string, number, null) but JSON objects can be translated into an array. The result is a singleton array that consists of the value before.
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- Any other conversion will throw a `std::logic_error` exception.
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When compatible, `JSON` values **implicitly convert** to `std::string`, `int`, `double`, `JSON::array_t`, and `JSON::object_t`. Furthermore, **explicit type conversion** is possible using the `get<>()` function with the aforementioned types.
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## Initialization
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JSON values can be created from many literals and variable types:
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| JSON type | literal/variable types | examples |
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| --------- | ---------------------- | -------- |
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| none | null pointer literal, `nullptr_t` type, no value | `nullptr` |
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| boolean | boolean literals, `bool` type, `JSON::boolean_t` type | `true`, `false` |
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| string | string literal, `char*` type, `std::string` type, `std::string&&` rvalue reference, `JSON::string_t` type | `"Hello"` |
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| number (integer) | integer literal, `short int` type, `int` type, `JSON_number_t` type | `42` |
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| number (floating point) | floating point literal, `float` type, `double` type, `JSON::number_float_t` type | `3.141529`
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| array | initializer list whose elements are `JSON` values (or can be translated into `JSON` values using the rules above), `std::vector<JSON>` type, `JSON::array_t` type, `JSON::array_t&&` rvalue reference | `{1, 2, 3, true, "foo"}` |
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| object | initializer list whose elements are pairs of a string literal and a `JSON` value (or can be translated into `JSON` values using the rules above), `std::map<std::string, JSON>` type, `JSON::object_t` type, `JSON::object_t&&` rvalue reference | `{ {"key1", 42}, {"key2", false} }` |
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