CODEWITHSUNDEEP
c++algorithmstlc++11
Johann Gerell
Johann Gerell

Reputation: 25581

What's the recommended way of iterating a container in C++11?

What's the recommended way of iterating a container in C++11?

Using

container.begin() and container.end()

Or

begin(container) and end(container)

If any, when is one preferred over the other?

Upvotes: 26

Views: 3688

Answers (2)

Basile Starynkevitch
Basile Starynkevitch

Reputation: 1

I think the new syntax with range based for loops

 for (auto item : container)

is probably the most C++11 like.

As others commented, you sometimes want auto& or  const auto& instead of auto.

Upvotes: 37

spraff
spraff

Reputation: 33385

The better way is

begin(container)
end(container)

because it's more extensible. For example, template argument deduction can be used to determine the size of a static array and hence begin(my_static_array) and end(my_static_array) will work.

More generally, you can add overloads/specialisations to begin(.) end(.) and use immutable legacy types in generic algorithms.

You really only need to worry about this if you're writing a generic algorithm youself

template <typename T>
void foo (T & t)
{
    bar (begin(t), end(t)); // certainly better than bar(t.begin(), t.end())
}

In client code it doesn't matter so much. In fact, I would say don't use the new form in that case -- I like to reserve certain styles/idioms for certain circumstances, divide my mindsets. But that's just me.

for (auto i = c.begin(); i != c.end(); ++i)
   // I can see at-a-glance that c is a STL-style container.
   // That might be useful to know. I can probably dismiss static arrays
   // and unorthodox containers as possibilities.
   foo (i, c.size());

Upvotes: 24

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