deploy: 7c9208bfb3

2026-07-09 03:55:09 +00:00 · 2026-07-08 18:19:46 +00:00
parent 9a231845c2
commit 279d757031
758 changed files with 56489 additions and 503 deletions
@@ -0,0 +1,81 @@
+# <small>nlohmann::basic_json::</small>value_t
+
+```cpp
+enum class value_t : std::uint8_t {
+    null,
+    object,
+    array,
+    string,
+    boolean,
+    number_integer,
+    number_unsigned,
+    number_float,
+    binary,
+    discarded
+};
+```
+
+This enumeration collects the different JSON types. It is internally used to distinguish the stored values, and the
+functions [`is_null`](is_null.md), [`is_object`](is_object.md), [`is_array`](is_array.md), [`is_string`](is_string.md),
+[`is_boolean`](is_boolean.md), [`is_number`](is_number.md) (with [`is_number_integer`](is_number_integer.md),
+[`is_number_unsigned`](is_number_unsigned.md), and [`is_number_float`](is_number_float.md)),
+[`is_discarded`](is_discarded.md), [`is_binary`](is_binary.md), [`is_primitive`](is_primitive.md), and
+[`is_structured`](is_structured.md) rely on it.
+
+## Notes
+
+!!! note "Ordering"
+
+    The order of types is as follows:
+
+    1. `null`
+    2. `boolean`
+    3. `number_integer`, `number_unsigned`, `number_float`
+    4. `object`
+    5. `array`
+    6. `string`
+    7. `binary`
+
+    `discarded` is unordered.
+
+!!! note "Types of numbers"
+
+    There are three enumerators for numbers (`number_integer`, `number_unsigned`, and `number_float`) to distinguish
+    between different types of numbers:
+
+      - [`number_unsigned_t`](number_unsigned_t.md) for unsigned integers
+      - [`number_integer_t`](number_integer_t.md) for signed integers
+      - [`number_float_t`](number_float_t.md) for floating-point numbers or to approximate integers which do not fit
+        into the limits of their respective type
+
+!!! warning "Comparison operators"
+
+    `operator<` and `operator<=>` (since C++20) are overloaded and compare according to the ordering described above.
+    Until C++20 all other relational and equality operators yield results according to the integer value of each
+    enumerator. Since C++20 some compilers consider the _rewritten candidates_ generated from `operator<=>` during
+    overload resolution, while others do not. For predictable and portable behavior use:
+
+      - `operator<` or `operator<=>` when wanting to compare according to the order described above
+      - `operator==` or `operator!=` when wanting to compare according to each enumerators integer value
+
+## Examples
+
+??? example
+
+    The following code how `type()` queries the `value_t` for all JSON types.
+    
+    ```cpp
+    --8<-- "examples/type.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/type.output"
+    ```
+
+## Version history
+
+- Added in version 1.0.0.
+- Added unsigned integer type in version 2.0.0.
+- Added binary type in version 3.8.0.