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nlohmann
88 lines
2.3 KiB
Markdown
88 lines
2.3 KiB
Markdown
# <small>nlohmann::basic_json::</small>operator<=
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```cpp
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// until C++20
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bool operator<=(const_reference lhs, const_reference rhs) noexcept; // (1)
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template<typename ScalarType>
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bool operator<=(const_reference lhs, const ScalarType rhs) noexcept; // (2)
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template<typename ScalarType>
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bool operator<=(ScalarType lhs, const const_reference rhs) noexcept; // (2)
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```
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1. Compares whether one JSON value `lhs` is less than or equal to another JSON value `rhs`
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according to the following rules:
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- The comparison always yields `#!cpp false` if (1) either operand is discarded, or (2) either
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operand is `NaN` and the other operand is either `NaN` or any other number.
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- Otherwise, returns the result of `#!cpp !(rhs < lhs)` (see [**operator<**](operator_lt.md)).
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2. Compares whether a JSON value is less than or equal to a scalar or a scalar is less than or equal
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to a JSON value by converting the scalar to a JSON value and comparing both JSON values according
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to 1.
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## Template parameters
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`ScalarType`
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: a scalar type according to `std::is_scalar<ScalarType>::value`
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## Parameters
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`lhs` (in)
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: first value to consider
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`rhs` (in)
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: second value to consider
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## Return value
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whether `lhs` is less than or equal to `rhs`
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## Exception safety
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No-throw guarantee: this function never throws exceptions.
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## Complexity
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Linear.
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## Notes
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!!! note "Comparing `NaN`"
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`NaN` values are unordered within the domain of numbers.
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The following comparisons all yield `#!cpp false`:
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1. Comparing a `NaN` with itself.
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2. Comparing a `NaN` with another `NaN`.
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3. Comparing a `NaN` and any other number.
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!!! note "Operator overload resolution"
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Since C++20 overload resolution will consider the _rewritten candidate_ generated from
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[`operator<=>`](operator_spaceship.md).
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## Examples
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??? example
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The example demonstrates comparing several JSON types.
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```cpp
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--8<-- "examples/operator__lessequal.cpp"
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```
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Output:
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```json
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--8<-- "examples/operator__lessequal.output"
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```
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## See also
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- [**operator<=>**](operator_spaceship.md) comparison: 3-way
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## Version history
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1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
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2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
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