C++ Algorithm Functions all_of()

C++ Algorithm all_of() function returns a true value if the value of 'pred' argument is true. The value should be true for all elements in the range [first, last].

Syntax

template <class InputIterator, class UnaryPredicate>
bool all_of (InputIterator first, InputIterator last, UnaryPredicate pred);

Parameter

first: It specifies the first element in the list.

last: It specifies the last element in the list.

pred: It is a unary function which accepts the argument from the range.

Return value

The function has one return type, 'true'. If the value of argument 'pred' is true for all the elements of the range then the value 'true' is returned, else false.

Example 1

#include<iostream>
#include<algorithm>
#include<array>
int main()
{
	std::array<int, 6> arr= {25,27,29,31,33,35};
	if ( std::all_of(arr.begin(), arr.end(), [](int k) {return k%2;} ) )
	std::cout <<"All the array elements are odd.";
	return 0;
}

Output:

All the array elements are odd.

Example 2

#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
	int ar[6] = {2, 5, -7, -9, 3, 5};
	all_of(ar, ar+6, [](int x) { return x>0; })?
	cout<<"All elements are positive \n":
	cout<<"All elements are not positive";
	return 0;
}

Output:

All elements are not positive

Complexity

The function moves linearly, starting from the first element going towards the last one. For each element of the list, the value of 'pred' is checked. The search goes on until a mismatch for the 'pred' value is encountered.