Where are the begin() and end() functions defined in C++?

Question

In cppreference.com, it states that the begin() and end() functions are defined in the header file < iterator >. But I still can use the begin() and end() functions without including the < iterator > header. I wonder why? Is it because I use;

using namespace std;

So it is included?

No, `using namespace xxx` doesn't include any header files. It only means that you can write `begin()` instead of `std::begin()`. The ` header must be included through some other header that you did include into your .cpp. — Violet Giraffe, Feb 25 '16 at 07:07
Unrelate to answer: Avoid writing `using namespace std;` in real code. — Mohit Jain, Feb 25 '16 at 07:10
@SH.C Check [this question](http://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice) — Mohit Jain, Feb 25 '16 at 07:12

score 9 · Accepted Answer · edited Feb 25 '16 at 07:10

9

Read from notes on the same page:

In addition to being included in <iterator>, std::begin is guaranteed to become available if any of the following headers are included: <array>, <deque>, <forward_list>, <list>, <map>, <regex>, <set>, <string>, <unordered_map>, <unordered_set>, and <vector>.

Apart from these list of headers, std::begin may get included from some other header also.

edited Feb 25 '16 at 07:10

Niall

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answered Feb 25 '16 at 07:08

Mohit Jain

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Oh, ok, I didn't see that. That make so much more sense. – BVBC Feb 25 '16 at 07:09

score 1 · Answer 2 · answered Feb 25 '16 at 07:07

1

No, using namespace xxx doesn't include any header files. It only means that you can write begin() instead of std::begin(). The <iterator> header must be included through some other header that you did include into your .cpp.

answered Feb 25 '16 at 07:07

Violet Giraffe

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Where are the begin() and end() functions defined in C++?

2 Answers2