std::deque<T,Allocator>::operator[] (3) - Linux Manuals

std::deque<T,Allocator>::operator[]: std::deque<T,Allocator>::operator[]

Command to display std::deque<T,Allocator>::operator[] manual in Linux: $ man 3 std::deque<T,Allocator>::operator[]

std::deque<T,Allocator>::operator[] - std::deque<T,Allocator>::operator[]

reference operator[]( size_type pos );
const_reference operator[]( size_type pos ) const;

Returns a reference to the element at specified location pos. No bounds checking is performed.

pos - position of the element to return

Reference to the requested element.

Constant.

Unlike std::map::operator[], this operator never inserts a new element into the container.

The following code uses operator[] to read from and write to a std::deque<int>:
// Run this code

#include <deque>
#include <iostream>

  int main()
  {
      std::deque<int> numbers {2, 4, 6, 8};

std::cout << "Second element: " << numbers[1] << '\n';

numbers[0] = 5;

      std::cout << "All numbers:";
      for (auto i : numbers) {
          std::cout << ' ' << i;
      }
      std::cout << '\n';
  }

Second element: 4
All numbers: 5 4 6 8