Re: [Boost-users] [Iterator]Can dereference() in iterator_adaptor return a temporary value?

Subject: Re: [Boost-users] [Iterator]Can dereference() in iterator_adaptor return a temporary value?
From: Nathan Ridge (zeratul976_at_[hidden])
Date: 2011-07-31 19:55:13

> Hi, I'd like a const iterator that acts as a proxy by giving access to 
> elements of type A as if they were elements of unrelated type B. In 
> that case I guess the dereference() member function should return a 
> temporary value, right? 
> Would that be a correct implementation of the idea? Here I just want to 
> access an array of SourceVertexType as if it were an array of 
> VertexType. 
> 
> template<class VertexType> 
> class ConstVerticesIterator : public boost::iterator_adaptor< 
> ConstVerticesIterator<VertexType>, const SourceVertexType*, const 
> VertexType > 

Yes, this is fine. This is what transform_iterator does.
 
However, you should specify the fourth template parameter of 
iterator_adaptor (Reference) to be "const VertexType" as well,
otherwise it will default to "const VertexType&" and operator*
will return a reference to the temporary rather than returning
a copy.
 
Regards,
Nate