[Boost-users] Re: How to make an iterator with a stride... and more

Maybe you should be looking at std::advance? Eli Pulsifer wrote:

Hello,

I have a situation which is probably quite common and already addressed by boost.

So rather than write it my self, maybe someone can point me to the answer.

I’ve got a geometry class that needs to expose iterators for the underling vertex components.

Example:

Class Vertex

{

positions_iterator PositionsBegin();

positions_iterator PositionsEnd();

normals_iterator NormalsBegin();

normals _iterator NormalsEnd();

…

}

The first problem is depending on the format of the underling vertices, the stride between the data elements will change.

Is there some easy way to implement this?

I think writing my own using the boost::iterator_adapter is probably the way to go.

Second problem is more involved.

The texture data not only has a stride but a variable number of elements.

Some vertices have 2 texture coordinates, some 3, some even more.

Id love to define this iterator like this:

stride_iterator< pair > tex_coord_iterator;

then create the iterator:

stride_tupel_iterator< pair >( pFirstTexCoord, texCoordStride, texCoordCount );

then use it:

stride_tupel_iterator< pair > it;

for( it = vertex.PositionBegin() ; it != vertex.PositionEnd() ; ++it)

{

pair coords;

float_iterator iCoord;

for(iCoord = coords.first ; iCoord != coords.last ; ++iCoord)

{

}

}

This will probably also require me to create my own highly special iterator class or is there a better way.

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