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[libcvd-members] Image creation input iterator.

From: Edward Rosten
Subject: [libcvd-members] Image creation input iterator.
Date: Wed, 5 Jul 2006 19:02:46 -0600 (MDT)

consider this:

vector<Image<byte> > v;

You want v to have 6 32x32 images. If you do this:

vector<Image<byte> > v(6, ImageRef(32,32));

you get 6 references to the same data, since if first constructs one 32x32 image (the argument to the vector constructor) and then copy-constructs 6 images from that, so they all share the same data.

A vector can take two iterators in the constructor, so with the ImageCreatorIterator input iterator, you can do this:

ImageCreatorIterator<ImageRef> begin(ImageRef(32, 32)), end(6);
vector<Image<byte> >  v(begin, end);

Or, the one line version (ie for use in constructors)

vector<Image<byte> > v(CreateImagesBegin(ImageRef(32, 32)), 
Unfortunately, this is rather ugly, especially this part     

The trouble is that the constructor for v is templated (simplified):

template<class C> class vector
                template<class I> vector(I& begin, I& end);

so it can't figure out in this case:

vector<Image<byte> > v(CreateImagesBegin(ImageRef(32, 32)), 6);

that it could use the templated constructor, and then construct a new iterator from the int.

Can anyone think of a nicer way of doing this (ie constructing an STL container so it starts with N distinct images).


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