putting primitive non pointer data types on stl vector

i have a struct

struct plane {
long int x, y, z;
};
I have vector of planes
std::vector<plane> PlaneVector;

Do I do
PlaneVector.resize(currentnumplanes)
or
PlaneVector.push_back(Plane()) (even though I provided no constructor)
or something else? I don't see why there are different ways to add stuff to a vector

i say push_back

http://www.cprogramming.com/tutorial/stl/vector.html

well doing push_back(Plane()) works just fine so I don't see the point in resize i guess msdn will tell me

Resize allows you to insert many elements in one call; albeit they must be the same.

PlaneVec.resize(32, plane(5,4,5));
// Inserts 32 plane objects all constructed with x=5 y=4 z=5

>>well doing push_back(Plane()) works just fine so I don't see the point in resize
push_back() and resize() do different things. resize() tells the vector to allocate enough space for N items so that multiple calls to push_back() are more efficient. push_back() allocates more space if needed, but doesn't if not needed, and then inserts a new item at the end.

To recap, resize() doesn't create N items, it only sets aside space for those items, push_back() actually adds them. So unless you really need exact performance, don't even worry about resize(), just use push_back().

Quote:

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To recap, resize() doesn't create N items, it only sets aside space for those items, push_back() actually adds them. So unless you really need exact performance, don't even worry about resize(), just use push_back().

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so if resize doesn't actually create N items, then that means push_back actually does create the items, which must mean it calls the constructor and resize doesn't, correct? kind of like new vs malloc

>then that means push_back actually does create the items
No, push_back() takes an already existing item and adds it to the vector.

OBJ o;
v.push_back(o);

Or you can call the constructor directly and push_back() takes the newly created object

v.push_back(OBJ());

But push_back() doesn't call the constructor at all.

Quote:

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Originally posted by Cela
>>well doing push_back(Plane()) works just fine so I don't see the point in resize
push_back() and resize() do different things. resize() tells the vector to allocate enough space for N items so that multiple calls to push_back() are more efficient. push_back() allocates more space if needed, but doesn't if not needed, and then inserts a new item at the end.

To recap, resize() doesn't create N items, it only sets aside space for those items, push_back() actually adds them. So unless you really need exact performance, don't even worry about resize(), just use push_back().

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I disagree... unless i'm missing something. Try this:

Code:

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std::vector<int> intlist;
intlist.resize(8, 5);
for (std::vector<int>::iterator i = intlist.begin(); i < intlist.end(); ++i)
        std::cout << *i;

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well it outputs 5 8 times as i suspected it would, im just using push back because it works.