1# basic_json::is_boolean 2 3```cpp 4constexpr bool is_boolean() const noexcept; 5``` 6 7This function returns `#!cpp true` if and only if the JSON value is `#!json true` or `#!json false`. 8 9## Return value 10 11`#!cpp true` if type is boolean, `#!cpp false` otherwise. 12 13## Exception safety 14 15No-throw guarantee: this member function never throws exceptions. 16 17## Complexity 18 19Constant. 20 21## Example 22 23??? example 24 25 The following code exemplifies `is_boolean()` for all JSON types. 26 27 ```cpp 28 --8<-- "examples/is_boolean.cpp" 29 ``` 30 31 Output: 32 33 ```json 34 --8<-- "examples/is_boolean.output" 35 ``` 36 37## Version history 38 39- Added in version 1.0.0. 40