Difference between revisions of "cpp/utility/functional/less equal"
From cppreference.com
< cpp | utility | functional
(~) |
m (~) |
||
| (5 intermediate revisions by 4 users not shown) | |||
| Line 2: | Line 2: | ||
{{cpp/utility/functional/navbar}} | {{cpp/utility/functional/navbar}} | ||
{{dcl begin}} | {{dcl begin}} | ||
| − | {{dcl header | functional }} | + | {{dcl header|functional}} |
{{dcl rev multi | {{dcl rev multi | ||
| − | | dcl1= | + | |dcl1= |
template< class T > | template< class T > | ||
struct less_equal; | struct less_equal; | ||
| − | | since2=c++14 | dcl2= | + | |since2=c++14|dcl2= |
template< class T = void > | template< class T = void > | ||
struct less_equal; | struct less_equal; | ||
| Line 13: | Line 13: | ||
{{dcl end}} | {{dcl end}} | ||
| − | Function object for performing comparisons. | + | Function object for performing comparisons. The main template invokes {{c|1=operator<=}} on type {{tt|T}}. |
| − | + | ||
| − | + | ||
===Specializations=== | ===Specializations=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc inc | cpp/utility/functional/dsc less_equal_void}} | + | {{dsc inc|cpp/utility/functional/dsc less_equal_void}} |
{{dsc end}} | {{dsc end}} | ||
| Line 26: | Line 24: | ||
===Member functions=== | ===Member functions=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc mem fun | operator() | nolink=true | checks if the first argument is ''less'' than or ''equal'' to the second}} | + | {{dsc mem fun|operator()|nolink=true|checks if the first argument is ''less'' than or ''equal'' to the second}} |
{{dsc end}} | {{dsc end}} | ||
| − | {{member | {{small|std::less_equal::}}operator() | 2= | + | {{member|{{small|std::less_equal::}}operator()|2= |
{{dcl begin}} | {{dcl begin}} | ||
| − | {{ | + | {{dcla|constexpr=c++14|1= |
| − | | | + | |
bool operator()( const T& lhs, const T& rhs ) const; | bool operator()( const T& lhs, const T& rhs ) const; | ||
| − | |||
| − | |||
}} | }} | ||
{{dcl end}} | {{dcl end}} | ||
| − | Checks if {{ | + | Checks if {{c|lhs}} is ''less'' than or ''equal'' to {{c|rhs}}. |
===Parameters=== | ===Parameters=== | ||
{{par begin}} | {{par begin}} | ||
| − | {{par | lhs, rhs | values to compare}} | + | {{par|lhs, rhs|values to compare}} |
{{par end}} | {{par end}} | ||
===Return value=== | ===Return value=== | ||
| − | + | {{c|1=lhs <= rhs}}. | |
| − | + | If {{tt|T}} is a pointer type, the result is consistent with the [[cpp/language/operator comparison#Pointer total order|implementation-defined strict total order over pointers]]. | |
{{cpp/impldef exception}} | {{cpp/impldef exception}} | ||
===Possible implementation=== | ===Possible implementation=== | ||
| − | {{eq fun | 1= | + | {{eq fun|1= |
| − | constexpr bool operator()(const T &lhs, const T &rhs) const | + | constexpr bool operator()(const T& lhs, const T& rhs) const |
{ | { | ||
| − | return lhs <= rhs; // assumes that the implementation | + | return lhs <= rhs; // assumes that the implementation handles pointer total order |
} | } | ||
}} | }} | ||
}} | }} | ||
| + | |||
| + | ===Defect reports=== | ||
| + | {{dr list begin}} | ||
| + | {{dr list item|wg=lwg|dr=2562|std=C++98|before=the pointer total order might be inconsistent|after=guaranteed to be consistent}} | ||
| + | {{dr list end}} | ||
| + | |||
| + | ===See also=== | ||
| + | {{dsc begin}} | ||
| + | {{dsc inc|cpp/utility/functional/dsc less}} | ||
| + | {{dsc inc|cpp/utility/functional/ranges/dsc {{SUBPAGENAMEE}}}} | ||
| + | {{dsc end}} | ||
{{langlinks|de|es|fr|it|ja|pt|ru|zh}} | {{langlinks|de|es|fr|it|ja|pt|ru|zh}} | ||
Latest revision as of 21:15, 13 July 2024
| Defined in header <functional>
|
||
template< class T > struct less_equal; |
(until C++14) | |
| template< class T = void > struct less_equal; |
(since C++14) | |
Function object for performing comparisons. The main template invokes operator<= on type T.
Contents |
[edit] Specializations
| (C++14) |
function object implementing x <= y deducing parameter and return types (class template specialization) |
[edit] Member types
| Type | Definition |
result_type (deprecated in C++17)(removed in C++20)
|
bool |
first_argument_type (deprecated in C++17)(removed in C++20)
|
T
|
second_argument_type (deprecated in C++17)(removed in C++20)
|
T
|
|
These member types are obtained via publicly inheriting std::binary_function<T, T, bool>. |
(until C++11) |
[edit] Member functions
| operator() |
checks if the first argument is less than or equal to the second (public member function) |
std::less_equal::operator()
bool operator()( const T& lhs, const T& rhs ) const; |
(constexpr since C++14) | |
Checks if lhs is less than or equal to rhs.
Parameters
| lhs, rhs | - | values to compare |
Return value
lhs <= rhs.
If T is a pointer type, the result is consistent with the implementation-defined strict total order over pointers.
[edit] Exceptions
May throw implementation-defined exceptions.
Possible implementation
constexpr bool operator()(const T& lhs, const T& rhs) const { return lhs <= rhs; // assumes that the implementation handles pointer total order } |
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2562 | C++98 | the pointer total order might be inconsistent | guaranteed to be consistent |
[edit] See also
| function object implementing x < y (class template) | |
| (C++20) |
constrained function object implementing x <= y (class) |
