c++ How can I append 3 values at once to a 2d array?

[fishies]

#ifndef __dot_h
#define __dot_h
#include <iostream>

struct dots
{
private:

dots();
~dots();
float points[3][3];
float mids[2][3];

public:

float x(int point);
float y(int point);
float z(int point);
void Init_dots();
void Add_dots(float x1,float y1, float z1);
void Add_dots(float x1,float y1, float z1,float x2, float y2, float z2);
void Print_dots();

};

dots:ots()
{

}

dots::~dots()
{
delete points;
delete mids;
}

float dots::x(int point)
{
return points[point-1][0];
}

float dots::y(int point)
{
return points[point-1][1];
}

float dots::z(int point)
{
return points[point-1][2];
}

void dots::Init_dots()
{
for(int i=0;i<((sizeof(points)/sizeof(float))-1)/3;i++)
{
for(int j=0;j<3;j++)
{
points[i][j]=i+j;
}
}
}

void dots::Add_dots(float x1,float y1, float z1)
{
points[(sizeof(points)/sizeof(float))/3]={x1,y1,z1};
}

void dots::Add_dots(float x1,float y1, float z1,float x2,float y2, float z2)
{
points[sizeof(points)/sizeof(float)]={x1,y1,z1};
points[sizeof(points)/sizeof(float)]={x2,y2,z2};
}

void dots::Print_dots()
{
for(int p=0;p<=(sizeof(points)/sizeof(float))-1;p++)
{
cout << points[p];
cout << "\n";
}
}



#endif;

The problem occurs in "Add_dots" fuction. I want to be able to append 3 vales to the 2d array all at once if this is possible. I am pretty new to programming so if you see any other errors/better ways of doing things I am open to suggestions. Thank you.

[Lindley]

Okay, what *exactly* are you trying to do here?

points[sizeof(points)/sizeof(float)]={x1,y1,z1};

I suggest never using sizeof() on an array type, because that'll get you into bad habits when you encounter dynamic arrays, first of all. Second, that index doesn't make any sense.

[fishies]

What I was trying to do is to append the three values to the end of the 2d array.

ex:

float points[3][3]={{x1,y1,z1},
{x2,y2,z2},
{x3,y3,z3}};

//then append three values..

points[3]={x4,y4,z4};

Hopefully this clarifies my question a little.

[VladimirF]

Hopefully this clarifies my question a little.

It does. And the answer is simple: you can't do it (change the size of an array).
You might want to use std::vector that allows dynamic resizing.

[Paul McKenzie]

What I was trying to do is to append the three values to the end of the 2d array.

You cannot do that -- arrays are fixed in size.

Why not just make it float points[4][3]?

If you want to add rows dynamically, use std::vector<std::vector<float> >.

Regards,

Paul McKenzie

[Paul McKenzie]

What I was trying to do is to append the three values to the end of the 2d array.

Also, it makes much more sense to have the 3 points in one structure:

#include <vector>
#include <iostream>

struct OnePoint
{
   float x;
   float y;
   float z;
   OnePoint(float px=0, float py=0, float pz=0) : x(px), y(py), z(pz) { }
};

std::vector<OnePoint> AllPoints;

using namespace std;

int main()
{
    AllPoints.push_back(OnePoint(0,43,1));
    AllPoints.push_back(OnePoint(2,6,1));
    AllPoints.push_back(OnePoint(-1,2,1));

    for (std::vector<OnePoint>::size_type i = 0; i < AllPoints.size(); ++i )
    {
        cout << AllPoints[i].x << " " 
               << AllPoints[i].y << " "
               << AllPoints[i].z << "\n";
    }
}

This prints out the 3 points that were added. You can add as many points as you want usint the push_back() method.

Regards,

Paul McKenzie

[fishies]

Also, it makes much more sense to have the 3 points in one structure

Paul McKenzie

Would it be possible to use that structure with 3 points in another structure? For example, a curve structure/class?


Thank you all for the information. I will learn how to use the std::vector.

[Paul McKenzie]

Would it be possible to use that structure with 3 points in another structure? For example, a curve structure/class?

Yes.

Regards,

Paul McKenzie

[Peter_APIIT]

Would it be possible to use that structure with 3 points in another structure? For example, a curve structure/class?

If you need to define a curve class, then you need to extend from base class which is two point one and add another point in derived class.


I hope this help.