How to use the all_of() function in C++

The all_of() function in C++ helps to determine if all the elements in the specified range satisfy the condition or not. This function is available in the <algorithm.h> header file.

Parameters

The all_of() function accepts the following parameters:

  • first: This is an iterator that points to the start index of the array or vector where we want to perform this check.

  • last: This is an iterator that points to the last index of the array or vector where we want to perform this check.

  • condition: This is a unary function that accepts one element of the same type as you have elements in the array or vector. This unary function returns a Boolean value that indicates whether the condition is satisfiedreturns true or notreturns false.

Return

The all_of() function returns a Boolean value true if all the elements in the range satisfied the condition; otherwise, it returns false.

Code

Let’s have a look at the code now.

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
bool AreAllOdd(int i){
  return (i % 2 == 1);
}
int main() {
  vector<int> vec = {3,5,7,11,13,17,19,23};
  if (all_of(vec.begin(), vec.end(), AreAllOdd))
    cout << "All the elements are odd numbers.";
  else
    cout << "All the elements are not odd numbers.";
  return 0;
}

Explanation

  • From lines 1 to 3, we import the required header files.
  • In line 6, we create our unary function that will return true if the number is odd; otherwise, it will return false.
  • In line 11, we create a vector of integers.
  • In line 13, we call the all_of() function and pass the required parameters.
  • Then, in line 14, we print if all the elements are odd. Otherwise, we print in line 16 that all the elements are not odd numbers.

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