🔒 Locked

std::insert_iterator help

Started by CRACK123 Aug 21, 2006 at 5:54 AM 1 reply 1.1k views

Original Post

Aug 21, 2006 at 5:54 AM

HI, I am trying to use the std::insert_iterator to copy data from a vector into another vector. I have the following code :-


	for(int i = 0; i < numFrames; i++)
	{
		const Frame *f = file.GetFrame(i);
		std::copy(f->m_Vertices.begin(), f->m_Vertices.end(),
				  std::insert_iterator<m_Vector.begin()>);
	}

This is incorrect and does not compile but I am not exactly understanding how the insert iterator work. I could use an index variable and do it this way but I want to know whats the right way to do it.


	std::copy(f->m_Vertices.begin(), f->m_Vertices.end(),
		  m_Vector.begin() + index);

Thanks

ToohrVyk

238

ToohrVyk

Aug 21, 2006 at 6:01 AM

Your two examples do not do the same thing. The first attempts to insert elements at a given position, the second overwrites elements starting at a given position. I suppose you want to do the former.

It is advised to use dest.insert(dest.begin()+n,origin.begin(),origin.end()), which is clearer and also more efficient.

You can also use std::copy(origin.begin(),origin.end(), std::insert_iterator >(dest,dest.begin()+n), which might be slower and less elegant.

Where T is the type of elements in your vector. See the documentation for more information.

joanusdmentia

Aug 21, 2006 at 7:12 AM

There's helper functions inserter, back_inserter and front_inserter for this:

#include <iterator>// Insert at frontstd::copy(f->m_Vertices.begin(), f->m_Vertices.end(), std::front_inserter(m_Vertices));// Insert at backstd::copy(f->m_Vertices.begin(), f->m_Vertices.end(), std::back_inserter(m_Vertices));// Insert somewhere in betweenstd::vector<Vertex>::iterator insertHere = ...;std::copy(f->m_Vertices.begin(), f->m_Vertices.end(), std::inserter(m_Vertices, insertHere));

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.