C++ vector manipulation optimization

Question

I'm trying to optimize the following code below to avoid having to copy and paste and just use SlaveForce and SlavePos properly, which are float[6] type, and baseForce and basePos are vector type:

typedef struct _NodeCoord
{
    float coords[6];
} NodeCoord;

int main()
{
    ...
    memcpy(tempNodeCoord.coords, SlaveForce, 6*sizeof(float));
    baseForce.push_back(tempNodeCoord);
    memcpy(tempNodeCoord.coords, SlavePos, 6*sizeof(float));
    basePos.push_back(tempNodeCoord);
    ...
}

I have tried some test codes. Only this appear to work:

std::vector<NodeCoord> tallon;
NodeCoord m;
memset(m.coords, 0, sizeof(m.coords));
tallon.push_back(m);

while this is along the lines of what I want to accomplish, but it doesn't work:

std::vector<float[6]> ed;
float e[6];
tallon.push_back(e);

I also tried writing a "typedef float[6] mytype;" line before the main function, but it doesn't work well either. Is there anything that I can do to eliminate the memcpy function calls (or rather push_back the float[6] variables directly)? Thanks in advance.

Answer 1

Try a vector of vectors:

std::vector<std::vector<float> > ed;

ed.push_back(std::vector<float>(6, 0.0f));

In this case I'm pushing a temp vector of floats, with 6 elements with the value of 0.0f;

Info on vector's constructors.

Answer 2

In order to be storable in a vector, a type must be copyable and assignable, and C-style arrays are neither. You should instead use another vector, or possibly wrap the array in a struct.

Answer 3

This is c++, why not try a class?

class NodeCoord { 
public:
    float coords[6];
    NodeCoord() {memset(coords, 0, sizeof(coords));};
    ~NodeCoord() {};
};

std::vector<NodeCoord> tallon;
tallon.push_back(NodeCoord());

cout << tallon.front().coords[0];

And you can do a lot more with the class, if you choose. If you wish to avoid copies, just make shallow copies of the class in a copy constructor.