std::less
From cppreference.com
< cpp | utility | functional
| Defined in header
<functional>
|
||
| template< class T >
struct less; |
(until C++14) | |
| template< class T = void >
struct less; |
(since C++14) | |
Function object for performing comparisons. Unless specialized, invokes operator< on type T.
Contents |
[edit] Specializations
If the built-in operator< does not provide total order for pointers, a partial specialization of std::less for pointer types is provided, which guarantees total order.
|
The standard library provides a specialization of
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(since C++14) |
[edit] Member types
| type | definition |
result_type
|
bool
|
first_argument_type
|
T
|
second_argument_type
|
T
|
[edit] Member functions
| operator() |
checks if the first argument is less than the second (public member function) |
std::less::operator()
| 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) | |
Checks whether lhs is less than rhs.
Parameters
| lhs, rhs | - | values to compare |
Return value
true if lhs < rhs, false otherwise.
Exceptions
(none)
Possible implementation
constexpr bool operator()(const T &lhs, const T &rhs) const { return lhs < rhs; } |
[edit] Example
Run this code
#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'; }
Output:
true false
[edit] See also
| (C++11)
|
provides mixed-type owner-based ordering of shared and weak pointers (class template) |