C++ <iterator> - cbegin() Function

The C++ <iterator> cbegin() function returns an iterator pointing to the first element in the sequence. The container's object is always treated as constant qualified and if the sequence is a standard container, the function always returns a const_iterator.

These function templates are defined in multiple headers which are: <iterator>, <array>, <deque>, <forward_list>, <list>, <map>, <regex>, <set>, <string>, <string_view>, <unordered_map>, <unordered_set> and <vector>.

Note: A const_iterator is an iterator that points to constant value. The difference between iterator and const_iterator is that the const_iterator cannot be used to modify the content it points to, even if the vector element is not itself constant.

Syntax

• C++14

template <class Container>
  constexpr auto cbegin (const Container& cont) noexcept
    -> decltype (begin(cont));

Parameters

Return Value

Returns an iterator to the first element of the sequence. The container's object is always treated as constant qualified and if the sequence is a standard container, the function always returns a const_iterator.

Example:

In the example below, the cbegin() function is used to iterate over an array to insert all elements of the array into a vector.

#include <iostream>
#include <iterator>
#include <vector>
using namespace std;
 
int main (){
  int arr[] = {10, 20, 30, 40, 50};
  vector<int> vec;

  //iterate over array to insert all elements
  //of the array into an empty vector
  for(auto it = cbegin(arr); it != cend(arr); ++it)
    vec.push_back(*it);

  //print the content of the vector
  cout<<"vec contains: ";
  for(auto it = cbegin(vec); it != cend(vec); ++it)
    cout<<*it<<" ";

  return 0;
}

The output of the above code will be:

vec contains: 10 20 30 40 50