Re: tokenizer: finding the last element. is it possible?

From: John Harris (john.harris_at_[hidden])
Date: 2003-04-29 16:35:57

> >how about: std::advance(first, std::distance(first,last)-1) ?
> >
> >The only requirement for distance() is that iterators be input 
> >iterators, which tokenizer's are.
> 
> This is an interesting solution. The downside is that the iterator 
would
> get advanced twice. I believe the implementation for distance for a
> forward iterator is to walk the iterator and count the distance. 
Then
> advance is going to do the same. This is efficient to type, but
> inefficient to run.

Of course.  But with an iterator modelling only the forward_iterator 
concept, there isn't much choice.  In fact the end() iterator can be 
just instantiated defaultly, as shown in a comment in the online 
docs.  This indicates that it contains no information that could be 
used for traversal.  You either have to copy the data out using the 
iterator or pay for the walking of it twice, like you said.

So something like this would work, too:

std::vector<std::string> v;
std::copy(begin, end, std::back_inserter(v));
// use v[v.size()-1] here