Jens Theisen wrote:

Hello,

I want to use indirect_iterator and noticed that it subscript operator returns a proxy.

I found the following explanation in iterator_facade.h:

// A proxy return type for operator[], needed to deal with // iterators that may invalidate referents upon destruction. // Consider the temporary iterator in *(a + n)

But I still don't understand why a proxy is necessary in some cases.

http://www.boost.org/libs/iterator/doc/iterator_facade.html#operator explains all. HTH, -- Dave Abrahams Boost Consulting http://www.boost-consulting.com