<functional>
template <class T> struct less;
Function object class for less-than inequality comparison
This class defines function objects for the "less than" inequality comparison operation.
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 regular function call, and therefore it can be used in templates instead of a pointer to a function.
less has its operator() member defined such that it returns true if its first argument compares lower than the second one using operator<, and false otherwise.
This class is derived from binary_function and is defined 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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Objects of this class can be used with some standard algorithms such as sort, merge or lower_bound.
Members
- T operator() (const T& x, const T& y)
- Member function returning the result of the comparison x<y.
Example
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// less example
#include <iostream>
#include <functional>
#include <algorithm>
using namespace std;
int main () {
int foo[]={10,20,5,15,25};
int bar[]={15,10,20};
sort (foo, foo+5, less<int>() ); // 5 10 15 20 25
sort (bar, bar+3, less<int>() ); // 10 15 20
if ( includes ( foo, foo+5, bar, bar+3, less<int>() ) )
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) |
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