Re: [boost] Iterator adaptors return a value from operator[]?

From: David Abrahams (dave_at_[hidden])
Date: 2002-08-17 13:09:31

From: "Anthony Williams" <anthwil_at_[hidden]>

> Can't we check whether [] returns a reference, somehow? It's not like
we're
> asking "what is the return value?", just is it T& or not, for known T,
> something like:
>
> template<typename T,typename IteratorType>
> struct checkSubscriptReturnIsRefToT
> {
>     template<typename V>
>     Big check(T& (IteratorType::*)(V));
>
>     Small check(...);
>
>     static const bool
>     result=(sizeof(check(&IteratorType::operator[])==sizeof(Big));
> };
>
> Obviously, we need to cope with const, volatile and const volatile
operator[],
> and versions taking different types of parameter, but I'm sure you can
fill in
> the details.

We've thought about it, and haven't come up with an answer. The details
(like the fact that operator[] might be overloaded, which pretty much rules
out the approach above) are non-trivial. If /you/ can fill in the details,
I'm interested. I've already tried and failed.

-----------------------------------------------------------
           David Abrahams * Boost Consulting
dave_at_[hidden] * http://www.boost-consulting.com