std::less

性病：减少

Defined in header
template< class T > struct less;		(until C++14)
template< class T = void > struct less;		(since C++14)

用于执行比较的函数对象。除非专门化，否则调用operator<论类型T...

专门性

...的专业化std::less对于任何指针类型，都会产生严格的总顺序，即使内置operator<不会的。严格的全序在专业之间是一致的。std::less，，，std::greater，，，std::less_equal，和std::greater_equal对于该指针类型，并且与相应的内建运算符%28施加的偏序一致。<，，，>，，，<=和>=29%。

If the function call operator of the specialization std::less calls a built-in operator comparing pointers, it yields a strict total order even if the built-in operator< does not.This strict total order is consistent among the specializations std::less, std::greater, std::less_equal, and std::greater_equal, and is also consistent with the partial order imposed by the corresponding built-in operators.

(since C++14)

The standard library provides a specialization of std::less when T is not specified, which leaves the parameter types and return type to be deduced. less function object implementing x < y deducing argument and return types (class template specialization)	less	function object implementing x < y deducing argument and return types (class template specialization)	(since C++14)
less<void>	function object implementing x < y deducing argument and return types (class template specialization)

成员类型

type	definition
result_type(deprecated in C++17)	bool
first_argument_type(deprecated in C++17)	T
second_argument_type(deprecated in C++17)	T

成员函数

operator()	checks if the first argument is less than the second (public member function)

STD：：较少：：操作员%28%29

bool operator()( const T& lhs, const T& rhs ) const;		(until C++14)
constexpr bool operator()( const T& lhs, const T& rhs ) const;		(since C++14)

检查是否lhs是再少点比rhs...

参数

lhs, rhs	-	values to compare

返回值

true如果lhs < rhs，，，false否则。

例外

%280%29

可能的实施

ConstT&rhs，constT&rhs%29 const{返回lhs<rhs；}

*。

例

二次

#include <functional>
#include <iostream>
 
template <typename A, typename B, typename U = std::less<int>>
bool f(A a, B b, U u = U())
{
    return u(a, b
}
 
int main() 
{
    std::cout << std::boolalpha;   
    std::cout << f(5, 20) << '\n';
    std::cout << f(100, 10) << '\n';
}

二次

产出：

二次

true
false

二次

另见

owner_less (C++11)	provides mixed-type owner-based ordering of shared and weak pointers (class template)
greater	function object implementing x > y (class template)

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