What does vector a(b) mean, in c++?

Question

Recently, I've started learning vector. I can't understand a syntax in vector. I googled it but couldn't find any satisfied answer.

std::vector<int> path;  
std::vector<int> newpath(path);

Can anyone explain this?

`vector` declares a `vector` which can contain `int` values. For detailed information search for C++ *templates*. — JimmyB, Aug 08 '18 at 08:35
Perhaps a [`std::vector` constructor reference](http://en.cppreference.com/w/cpp/container/vector/vector) might help? — Some programmer dude, Aug 08 '18 at 08:35
More specifically: Have you ever heard of *copy-constructors*? If not then it's time [to get some books to read](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list/388282#388282), from the start. — Some programmer dude, Aug 08 '18 at 08:36
@Jarod42 If `path` is to be copied to then be modified to create a new path, `newpath` is a sensible name to me. — JimmyB, Aug 08 '18 at 08:37
@JimmyB: even `path` is a strange name, `std::vector path;` or `std::vector numbers;` seems more appropriate. — Jarod42, Aug 08 '18 at 08:40

score 0 · Accepted Answer · edited Aug 08 '18 at 08:56

0

The second line copy-constructs a new std::vector<int> instance from path. Thereafter both vectors store identical data.

edited Aug 08 '18 at 08:56

Walter

answered Aug 08 '18 at 08:36

lubgr

Is _identical_ a reserved terminology for objects having equal salient non-salient objects? I meant value-equality in terms of `operator ==`, where `capacity()` and `data()` doesn't come into play. But I'm happy to adjust the wording if `identical` actually means something different. – lubgr Aug 08 '18 at 08:55
I think the word you're after is *equivalent*, i.e. compare equal with `operator==`. – Walter Aug 08 '18 at 08:57
@Walter Thanks for the fix! I don't know whether _equivalent_ is the right word either, though. Equality is a form of equivalence, but not the only one. I guess _equality_ is the best term here. – lubgr Aug 08 '18 at 09:01

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