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66 lines
1.6 KiB
Markdown
66 lines
1.6 KiB
Markdown
# <small>nlohmann::basic_json::</small>boolean_t
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```cpp
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using boolean_t = BooleanType;
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```
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The type used to store JSON booleans.
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[RFC 8259](https://tools.ietf.org/html/rfc8259) implicitly describes a boolean as a type which differentiates the two
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literals `#!json true` and `#!json false`.
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To store boolean values in C++, a type is defined by the template parameter `BooleanType` which chooses the type to use.
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## Template parameters
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`BooleanType`
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: the type to store booleans. As it is stored directly inside a `basic_json` value (in a union), it must be a
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trivially default-constructible, trivially copyable, and trivially destructible type that is convertible to and
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from `#!cpp bool`. See
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[Template Parameter Requirements](../../features/types/template_parameters.md#booleantype).
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## Notes
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### Default type
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With the default values for `BooleanType` (`#!cpp bool`), the default value for `boolean_t` is `#!cpp bool`.
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### Storage
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Boolean values are stored directly inside a `basic_json` type.
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## Examples
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??? example
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The following code shows that `boolean_t` is by default, a typedef to `#!cpp bool`.
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```cpp
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#include <iostream>
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#include <iomanip>
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#include <nlohmann/json.hpp>
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using json = nlohmann::json;
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int main()
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{
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std::cout << std::boolalpha << std::is_same<bool, json::boolean_t>::value << std::endl;
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}
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```
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Output:
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```json
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true
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```
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## See also
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- [is_boolean](is_boolean.md) checks whether the JSON value is a boolean
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## Version history
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- Added in version 1.0.0.
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