C++ Iterator Library - begin

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Description

It returns an iterator pointing to the first element in the sequence.

Declaration

Following is the declaration for std::begin.

C++11

template <class Container>
  auto begin (Container& cont) -> decltype (cont.begin());
template <class Container>
  auto begin (const Container& cont) -> decltype (cont.begin());

Parameters

• cont − It is an object of a class type for which member begin is defined.

• arr − It is an array.

Return value

It returned by cont.begin().

Exceptions

If any of the arithmetical operations performed on the iterator throws.

Time complexity

constant for random-access iterators.

Example

The following example shows the usage of std::begin.

#include <iostream>     
#include <vector>       

int main () {
   int foo[] = {1,2,3,4,5};
   std::vector<int> bar;
  
   for (auto it = std::begin(foo); it!=std::end(foo); ++it)
      bar.push_back(*it);
  
   std::cout << "bar contains:";
   for (auto it = std::begin(bar); it!=std::end(bar); ++it)
      std::cout << ' ' << *it;
   std::cout << '\n';

   return 0;
}

Let us compile and run the above program, this will produce the following result −

bar contains: 1 2 3 4 5