iterator undeclared error?

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?

Code:

---

#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

you have using namespace std;

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

Quote:

---

Originally posted by ChuckB

Code:

---

...
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:

Code:

---

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

---

And just use vec_it as the type.

Z.

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.

Code:

---

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

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

Code:

---

&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.

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:

Code:

---

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

---

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.

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

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.

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

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() :)