iterator undeclared error?

[ChuckB]

Hi,

I can create a vector. I need an iterator so I can index the vector I have created. However, I get an error "Iterator undeclared" when I do this. What is missing?

#include <vector>
#include <iterator>

. . .

header.num_vertices=200;
std::vector<VERTEX> v;
v.resize(header.num_vertices);
std::iterator idx;
idx=v.begin();

VERTEX is a structure of x,y and z floats.

Regards,
ChuckB

[Daok]

you have using namespace std;

or using std::vector; using std:iterator;

[Zaei]

Originally posted by ChuckB

...
std::vector<VERTEX> v;
v.resize(header.num_vertices);
std::vector<VERTEX>::iterator idx;
idx=v.begin();

The iterator is an inner class of the container. Create them like the above. In many cases, you can typedef them, as well:

class myClass
{
public:
  std::vector<int> x;
  typedef std::vector<int>::iterator vec_it;
};

And just use vec_it as the type.

Z.

[ChuckB]

Hi,
Thanks for the correct format. I had actually just figured it out before logging in. ;-)

I have my first binary read/write functions that utilize vectors. I can save the number of textures, vertices and quads to a file and retrieve the data...all in binary. I did create a header to help me track it all. With the help of sizeof() I can get just about anything done.

One question though. I have a 'vertex' vector v[100], for example. I tried writing the entire vector to the file at one time...but it didn't like that. I had to write one vector element at a time. Is there a way to grab the whole vector.

for (int x=1;x<header.num_vertices +1;x++)
   fwrite(&v[x],sizeof(v[x]),1,fp);

Also, I couldn't get the iterator to work as I wanted...so I went back to using 'x' above. I was hoping to iterate through the vectors with iter++.

Regards,
ChuckB

[Zaei]

You could PROBABLY write the vector out like this by taking the address of the first item in the vector:

&v[0]

Like I said before, you have to be careful with this, because the standard does NOT specify how a container is represented internally, so you dont actually know if the internal buffer is a raw pointer or not.

Z.

[CornedBee]

Since pointers can be used as iterators, you could maybe load a bunch of vectors into a temporary mem block and then use vector::insert to insert them like this:

VERTEX buffer[10];
// fill the buffer
vec.insert(buffer, buffer+10);

[ChuckB]

Hi,
My VB World Map maker is working fine. I can create tons of vertices for QUADS for my 3D world.

I am reading an ASCII text file (for now) and loading the values into a vector. This is working provided I tell the function how many lines to read. Here is the short section of code.

  VERTEX v;
  char oneLine[255];
  FILE *fp;
  fp=fopen("mydata.dat","rt");
  q.reserve(96);                            //< --- hardcoded
  q.begin();
  for (int i=0;i<95;i++){                //< --- hardcoded
      ReadString(fp,oneLine);
      sscanf(oneLine,"%f, %f, %f", &v.x,&v.y,&v.z);
      q[i]=v;
  }
  fclose(fp);

Now, I know how to get VB to save the number of vertices at the top of the file as Z has suggested before. However, I would like to make this code go dynamically without knowing this number in advance.

So, any clues on how to increment to read all vertices from the file? I think I need to change the 'for' line to read something like:

for (vector::iterator iter = v.begin();iter < v.end();iter++)...etc.

After I get the vectors figures out completely I will be adding a header to my vertex files and saving in binary...so this exercise is academic for me...I want to know how to do it. :-)

It has been said before that arrays are faster than vectors. Are we talking about a lot of time difference regarding that?

Regards,
ChuckB

[CornedBee]

No, not really. Since loading is done only once and the really slow thing is the disk operation the overhead from possible reallocations of the vector is neglectible. Reading from a vector is basically just a range test and one (possibly inlined) function call of overhead, so that's not too bad.

[ChuckB]

CornedBee,
Cool! Vectors sound cooler than arrays. :-) I'll use them.

Any idea on how to dynamically increase the size when required like REDIM PRESERVE array(x) in VB?


Regards,
ChuckB

[parksie]

It'll do it automatically. However, you can give it a hint if you know vaguely what you're going to put into it. Use .reserve()