std::less
From cppreference.com
< cpp | utility | functional
Defined in header
<functional>
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||
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
The partial specialization of std::less
for any pointer type yields a total order, even if the built-in operator< does not.
The standard library provides a specialization of
|
(since C++14) |
[edit] Member types
type | definition |
result_type
|
bool
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first_argument_type
|
T
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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) |