Can I do vector.insert( vector.end(), vector.cbegin(), vector.cend() ) ?

SAn

I want to duplicate content of std::vector.

I thought about possible realisations of std::vector::insert(), and all of them should crash in case of iterators aliasing mentioned in the caption. But I have not found any mentions of aliasing in descriptions of the function. Any ideas? will it crash? What is the best, C++ way of duplicate vector content?

CStoll

First: There is no function cbegin() or cend() in vector<> only different overloads for begin()/end().

Second: While inserting the new elements, the vector might reallocate its memory and therefore invalidate all iterators referencing its context (inclusive the ones you used as source).

Third: One solution would be, doubling the size of the vector via resize() and using std::copy to fill its second half. Another idea ist to push_back() the elements one by one (using operator[] to get the source values).

SAn

Hmm. In Visual studio I always used cbegin() / cend() to get const iterator even of non-const vector. I use this to not accidentally modify vector data.

Ok, I see:

std::vector<T> v;

...

v.resize(v.size() * 2);
std::vector<T>::iterator const middle(v.begin() + v.size() / 2);
std::copy(v.begin(), middle, middle);

for(std::vector<T>::iterator i(middle); i != v.end(); ++i)
	i->someAdditionalProcessing();

Thank you.

But... I just read that std::vector::reserve() guarantees that no reallocation will take place. So, may it will be better to do this:

v.reserve(v.size() * 2);
v.insert( v.end(), v.begin(), v.end() );

for(std::vector<T>::iterator i(v.begin() + v.size() / 2); i != v.end(); ++i)
	i->someAdditionalProcessing();

theta

First: There is no function cbegin() or cend() in vector<> only different overloads for begin()/end().

There is.. at least in the current implementation which comes with VS2010 - i guess it is a C++11 feature.

C++ Forumbot

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