vector

[mickey]

HI, I need a vector such that every elemet is an array of 4 elements; I try this....but I don't sure it works....but then must use in setLight

std::vector <GLfloat>position[4];
position->push_back(1);
position[0][0] = 0.0f;
position[0][1] = 1.0f;
position[0][2] = 2.0f;
position[0][3] = 0.0f;
glLightfv(GL_LIGHT0, GL_POSITION, position[0]); //this don't compile

std::vector <GLfloat>position[4];
position->push_back(1);
position[0][0] = 0.0f;
position[0][1] = 1.0f;
position[0][2] = 2.0f;
position[0][3] = 0.0f;
glLightfv(GL_LIGHT0, GL_POSITION, position[0]); //this don't compile

To copy to clipboard, switch view to plain text mode 

[jcr]

vould

std::vector<std::vector<int> > cont;
  std::vector<int> temp;
  temp.push_back(1);
  temp.push_back(2);
  temp.push_back(3);
  temp.push_back(4);
  cont.push_back(temp);
  int k;
  k = cont[0][0];

std::vector<std::vector<int> > cont;
  std::vector<int> temp;
  temp.push_back(1);
  temp.push_back(2);
  temp.push_back(3);
  temp.push_back(4);
  cont.push_back(temp);
  int k;
  k = cont[0][0];

To copy to clipboard, switch view to plain text mode 

do the trick?

[jacek]

glLightfv(GL_LIGHT0, GL_POSITION, position[0]); //this don't compile

It's because OpenGL doesn't know anything about STL containers --- it's a C library.

Since std::vector keeps all elements in a single block, you can try:

glLightfv( GL_LIGHT0, GL_POSITION, &(position[0][0]) );

glLightfv( GL_LIGHT0, GL_POSITION, &(position[0][0]) );

To copy to clipboard, switch view to plain text mode 

[mickey]

It's compile! But I see that sometimes the instructions below get 'debug error'...What's the problem?

std::vector <GLfloat>position[4];
position->push_back(1);
position[0][0] = 0.0f;
position[0][1] = 1.0f;
position[0][2] = 2.0f;
position[0][3] = 0.0f;

std::vector <GLfloat>position[4];
position->push_back(1);
position[0][0] = 0.0f;
position[0][1] = 1.0f;
position[0][2] = 2.0f;
position[0][3] = 0.0f;

To copy to clipboard, switch view to plain text mode 

[jacek]

std::vector <GLfloat>position[4];

I hope you realize that this is an array of 4 vectors, not vector of 4-element arrays.

[mickey]

I suspected this; but in first post you 'didn't correct me'... and I was believing that!
Re-post first question; I need a <vector> such that every element is an array[4];
---
In realty, I have declare vector<GLfloat> pos[4] inside a class declaration! So I think it's OK(?). I can't create instance in class declaration(???).

[jacek]

I need a <vector> such that every element is an array[4];

Then try this:

std::vector< GLfloat[4] > position;

std::vector< GLfloat[4] > position;

To copy to clipboard, switch view to plain text mode 

[mickey]

hi, this below compile but I've problem to insert element:

std::vector <GLfloat[4]> pos;
std::vector <GLfloat[4]> pos(1); //don't compile
pos.push_back(?); how to insert element?

std::vector <GLfloat[4]> pos;
std::vector <GLfloat[4]> pos(1); //don't compile
pos.push_back(?); how to insert element?

To copy to clipboard, switch view to plain text mode 

[jacek]

hi, this below compile but I've problem to insert element:

std::vector< GLfloat[4] > pos;
GLfloat p[4];
p[0] = 0.0f;
p[1] = 1.0f;
p[2] = 2.0f;
p[3] = 3.0f;
pos.push_back( p );

std::vector< GLfloat[4] > pos;
GLfloat p[4];
p[0] = 0.0f;
p[1] = 1.0f;
p[2] = 2.0f;
p[3] = 3.0f;
pos.push_back( p );

To copy to clipboard, switch view to plain text mode 

[mickey]

Hi, I've alreadt tried this but compiler says me

C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\vector(810): error C2440: 'initializing' : cannot convert from 'const GLfloat [4]' to 'float [4]'

C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\vector(810): error C2440: 'initializing' : cannot convert from 'const GLfloat [4]' to 'float [4]'

To copy to clipboard, switch view to plain text mode 

If I change to this:

std::vector <float[4]> position;
float pos[4];
pos[0] = 0.0;
pos[1] = 1.0;
pos[2] = 0.0;
pos[3] = 0.0;
position.push_back(pos);

std::vector <float[4]> position;
float pos[4];
pos[0] = 0.0;
pos[1] = 1.0;
pos[2] = 0.0;
pos[3] = 0.0;
position.push_back(pos);

To copy to clipboard, switch view to plain text mode 

compiler get me the same error.....?!

[wysota]

Then use the const_cast to get rid of "const" or create your arrays on heap:

std::vector <GLfloat*> position;
GLfloat *pos new GLfloat[4];
pos[0] = 0.0;
pos[1] = 1.0;
pos[2] = 0.0;
pos[3] = 0.0;
position.push_back(pos);

std::vector <GLfloat*> position;
GLfloat *pos new GLfloat[4];
pos[0] = 0.0;
pos[1] = 1.0;
pos[2] = 0.0;
pos[3] = 0.0;
position.push_back(pos);

To copy to clipboard, switch view to plain text mode 

And remember to delete[] the array when you no longer need it to avoid memory leaks.

Or better yet, make your own class, something like:

struct MyData {
  MyData(GLfloat d1, GLfloat d2, GLfloat d3, GLfloat d4){ d[0] = d1; d[1]=d2; d[2]=d3; d[3]=d4;}
  GLfloat d[4];
  GLfloat & operator[](int i){ return d[i]; }
}
 
std::vector<MyData> pos;
pos.push_back(MyData(0.0, 1.0, 2.0, 3.0));

struct MyData {
  MyData(GLfloat d1, GLfloat d2, GLfloat d3, GLfloat d4){ d[0] = d1; d[1]=d2; d[2]=d3; d[3]=d4;}
  GLfloat d[4];
  GLfloat & operator[](int i){ return d[i]; }
}

std::vector<MyData> pos;
pos.push_back(MyData(0.0, 1.0, 2.0, 3.0));

To copy to clipboard, switch view to plain text mode 

[mickey]

thanks, the first example compile, but I'm trying to understand better the thing trying const_cast....but don't compile this...

GLfloat* p = const_cast <GLfloat[4]> (pos);
//const_cast <GLfloat[4]> (pos); //has it sense?
position.push_back(p); //this don't compile

GLfloat* p = const_cast <GLfloat[4]> (pos);
//const_cast <GLfloat[4]> (pos); //has it sense?
position.push_back(p); //this don't compile

To copy to clipboard, switch view to plain text mode 

[wysota]

const_cast may not work here or may cause segfaults later on, as you create those arrays on stack and when you push them onto the vector, you'll only push the pointer to the array, which will become invalid when the array goes out of scope. So you should stick with creating those items on heap like in my first example.