std::less in C++ with Examples
The std::less is a member of the functional class (<functional.h>) used for performing comparisons. It is defined as a function object class for less than inequality comparison which returns a boolean value depending upon the condition. This can be used to change the functionality of the given function. It can be used with various standard algorithms like sort, lower_bound etc.
Header File:
#include <functional.h>
Template Class:
template <class T> struct less {
// Declaration of the less operation
bool operator() (const T& x,
const T& y)
const
{
return x < y;
}
// Type of first parameter
typedef T first_argument_type;
// Type of second parameter
typedef T second_argument_type;
// The result is returned
// as bool type
typedef bool result_type;
};
Syntax:
std::less()
Parameter: This function accepts the type of the arguments T, as the parameter, to be compared by the functional call.
Return Type: It return a boolean value depending upon condition(let a & b are 2 element):
- True: If a is less than b.
- False: If a is greater than b.
Time Complexity: O(1)
Auxiliary Space: O(1)
Below is the illustration of std::less in C++:
Program 1:
CPP14
#include <algorithm>
#include <functional>
#include <iostream>
using namespace std;
void printArray( int arr[], int N)
{
for ( int i = 0; i < N; i++) {
cout << arr[i] << ' ' ;
}
}
int main()
{
int arr[] = { 26, 23, 21, 22,
28, 27, 25, 24 };
int N = sizeof (arr) / sizeof (arr[0]);
sort(arr, arr + N, less< int >());
printArray(arr, N);
return 0;
}
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Output:
21 22 23 24 25 26 27 28
Program 2:
CPP14
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
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()
{
int X = 1, Y = 2;
cout << std::boolalpha;
cout << f(X, Y) << '\n' ;
X = 2, Y = -1;
cout << f(X, Y) << '\n' ;
return 0;
}
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Reference: http://www.cplusplus.com/reference/functional/less/
Last Updated :
07 May, 2023
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