class template
<functional>
std::less
template <class T> struct less;
Function object class for less-than inequality comparison
Binary function object class whose call returns whether the its first argument compares less than the second (as returned by operator <).
Generically, function objects are instances of a class with member function operator() defined. This member function allows the object to be used with the same syntax as a function call.
It is defined with the same behavior as:
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| template <class T> struct less : binary_function <T,T,bool> { bool operator() (const T& x, const T& y) const {return x<y;} };
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| template <class T> struct less { bool operator() (const T& x, const T& y) const {return x<y;} typedef T first_argument_type; typedef T second_argument_type; typedef bool result_type; };
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Objects of this class can be used on standard algorithms such as sort, merge or lower_bound.
Template parameters
- T
- Type of the arguments to compare by the functional call.
The type shall support the operation (operator<).
Member types
| member type | definition | notes |
|---|
| first_argument_type | T | Type of the first argument in member operator() |
| second_argument_type | T | Type of the second argument in member operator() |
| result_type | bool | Type returned by member operator() |
Member functions
- bool operator() (const T& x, const T& y)
- Member function returning whether the first argument compares less than the second (
x<y).
Example
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| // less example #include <iostream> // std::cout #include <functional> // std::less #include <algorithm> // std::sort, std::includes int main () { int foo[]={10,20,5,15,25}; int bar[]={15,10,20}; std::sort (foo, foo+5, std::less<int>()); // 5 10 15 20 25 std::sort (bar, bar+3, std::less<int>()); // 10 15 20 if (std::includes (foo, foo+5, bar, bar+3, std::less<int>())) std::cout << "foo includes bar.\n"; return 0; }
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Output:
See also
- equal_to
- Function object class for equality comparison (class template)
- not_equal_to
- Function object class for non-equality comparison (class template)
- greater
- Function object class for greater-than inequality comparison (class template)
- greater_equal
- Function object class for greater-than-or-equal-to comparison (class template)
- less_equal
- Function object class for less-than-or-equal-to comparison (class template)