Re: Heterogeneous collection: return type overload

James Kanze <>
Thu, 18 Feb 2010 12:04:14 -0800 (PST)
On Feb 18, 6:50 am, jrbcast <> wrote:

On Feb 17, 7:59 pm, "Leigh Johnston" <> wrote:

"jrbcast" <> wrote in message

Imagine I have something like this:

class Collection
std::map<char *, void *> elements;

Using a char* as a key in a map is probably not a very good


Try "std::map<std::string, boost::any> elements;" instead.

Thanks for your responses. Now it is clear that C++ does not
support function overloading on return types :-(.

Not directly, but it's fairly simple to get the same effect by
means of a proxy:

    class Collection
        class Proxy
            Collection const* owner;
            std::string key;
            Proxy(Collection const& owner, std::string const& key)
                : owner(&owner)
                , key(key)
            template< typename T > operator T() const
                return owner->... // whatever it takes to get
                                   // the correctly typed value
        Proxy get(std::string const& key) const
            return Proxy(*this, key);
        // ...

James Kanze

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