C++, with vector can I push_back({someNum1,someNum2})?

Question

I have the vector:

vector<int[2]> storeInventory; //storeInventory[INDEX#]{ITEMNUM, QUANTITY}

and I am wanting to use the push_back() method to add new arrays to the inventory vector. Something similar to this:

const int ORANGE = 100001;
const int GRAPE = 100002

storeInventory.push_back({GRAPE,24});
storeInventory.push_back{ORANGE, 30};

However, when I try using the syntax as I have above I get the error Error: excpeted an expression. Is what I am trying just not possible, or am I just going about it the wrong way?

use std::pair instead of the array or use std::map – stefan Nov 30 '12 at 19:26 — stefan, Nov 30 '12 at 19:26

AnT stands with Russia · Accepted Answer · 2012-11-30T19:38:20.343

6

Built-in arrays are not Assignable or CopyConstructible. This violates container element requirements (at least for C++03 and earlier). In other words, you can't have std::vector of int[2] elements. You have to wrap your array type to satisfy the above requirements.

As it has already been suggested, std::array in a perfect candidate for a wrapper type in C++11. Or you can just do

struct Int2 {
  int a[2];
};

and use std::vector<Int2>.

edited Nov 30 '12 at 19:38

answered Nov 30 '12 at 19:32

AnT stands with Russia

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Technically, I think `vector storeInventory;` is valid in C++11 with the new fine-grained container requirements. The value type needs only be _destructible_, which an array type is. `push_back` requires that the value type is copy insertable, which an array type is not. A container of an array type is not very usable (or useful), and using a wrapper structure (like `std::array`) would be advisable. – James McNellis Nov 30 '12 at 19:37

score 3 · Answer 2 · answered Nov 30 '12 at 19:30

3

I don't believe it's possible to pass arrays like that. Consider using std::array instead:

vector<std::array<int, 2> > storeInventory; 
storeInventory.push_back({{GRAPE,24}});

answered Nov 30 '12 at 19:30

Pubby

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score 3 · Answer 3 · answered Nov 30 '12 at 21:07

3

If it's only vector of int[2] you could use:

std::vector<std::pair<int, int>> vec

Adding elements:

int a, b;
vec.push_back(std::make_pair(a, b));

answered Nov 30 '12 at 21:07

score 2 · Answer 4 · edited Nov 30 '12 at 19:25

2

storeInventory.push_back({GRAPE, 24});
storeInventory.push_back({ORANGE, 30});

You can try this. I think you forgot parentheses.

edited Nov 30 '12 at 19:25

David G

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answered Nov 30 '12 at 19:25

Övünç Metin

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4

Unfortunately this doesn't work, which is why I am asking this question. – Brook Julias Nov 30 '12 at 22:02

score 2 · Answer 5 · answered Nov 30 '12 at 19:32

2

C-style arrays are not copyable, so can't be used as the element type in a std::vector.

answered Nov 30 '12 at 19:32

Pete Becker

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score 0 · Answer 6 · answered May 22 '15 at 19:17

0

Simply use a std::vector<int *> :)

answered May 22 '15 at 19:17

Klauz

1

This answer could be improved if it made more of an effort to explain to the asker why this solution would work and how they should apply it. – nhgrif May 22 '15 at 22:43

C++, with vector can I push_back({someNum1,someNum2})?

6 Answers6

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