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std::less_equal in C++ with Examples

  • Difficulty Level : Basic
  • Last Updated : 01 May, 2020

The std::less_equals is a function object class used for performing comparisons. It is defined as a function object class for less than equality comparison which returns a boolean value depending upon the condition. It can be used with various standard algorithms like sort, lower_bound and containers like vector, set, etc.

Header File:

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#include <functional.h>

Template Class:

template <class T> struct less_equal {

  // Declaration of the 
  // less equal 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::bind2nd(std::less_equal(), K)

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 equals to b.
  • False: If a is greater than b.

Below is the illustration of std::less_equal in C++:

Program 1:




// C++ program to illustrate less_equal
#include <algorithm>
#include <functional>
#include <iostream>
using namespace std;
  
// Function to print the array arr[]
void printArray(int arr[], int N)
{
  
    for (int i = 0; i < N; i++) {
        cout << arr[i] << ' ';
    }
}
  
// Driver Code
int main()
{
    int arr[] = { 1, 5, 8, 9, 6,
                  7, 3, 4, 2, 0 };
  
    int N = sizeof(arr) / sizeof(arr[0]);
  
    // Sort the array in increasing order
    sort(arr, arr + N, less_equal<int>());
  
    // Print sorted array
    printArray(arr, N);
    return 0;
}
Output:
0 1 2 3 4 5 6 7 8 9

Program 2:




// C++ program to illustrate less_equal
#include <functional>
#include <iostream>
#include <iterator>
#include <set>
using namespace std;
  
// Driver Code
int main()
{
    // Initialise set with less_equal to
    // store the elements in increasing
    // order
    set<int, less_equal<int> > S;
  
    // Insert elements in S
    S.insert(75);
    S.insert(30);
    S.insert(60);
    S.insert(20);
    S.insert(50);
    S.insert(30);
  
    // Print the elements stored in set S
    for (auto& it : S) {
        cout << it << ' ';
    }
  
    return 0;
}
Output:
20 30 30 50 60 75

Reference: http://www.cplusplus.com/reference/functional/less_equal/




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