From: "Reece Dunn" <msclrhd@hotmail.com>
Rob Stewart wrote:
From: "Reece Dunn" <msclrhd@hotmail.com>
Currently, this implementation is missing iterator support (and thus all basic_string functionality that relies on begin(), end(), etc). This is because I am wondering how to map them from the basic_string adaptor to
the
implementation (knowing that you cannot have const and non-const virtual functions).
Since when can you not have const and non-const virtual functions?
Let me rephrase:
class char_string { virtual iterator begin() = 0; virtual const_iterator begin() = 0; // oops! begin already in vtable!! };
I'm still missing something. Why would you want a non-const mf to return the const iterator type? class char_string { virtual iterator begin() = 0; virtual const_iterator begin() const = 0; };
I have two possible solutions: [1] name the const versions cXXX (cbegin(), crend(), etc.) -- the problem with this is that you have 8 virtual functions!
I was meaning to modify the above to:
class char_string { virtual iterator begin() = 0; virtual const_iterator cbegin() = 0; // ok - cXXX variant };
You'd have those same eight variations with const and non-const virtual functions.
That's the problem -- too many virtual functions.
But if you need all eight variations, then you need eight virtual functions. Is it that you're trying to minimize what the derived class must implement for the adaptor to work? Even if that's the case, because the const and non-const functions return different types, you can't have the derived class implement a const implementation function that the adaptor can use to provide both const and non-const interface functions. So what am I missing? -- Rob Stewart stewart@sig.com Software Engineer http://www.sig.com Susquehanna International Group, LLP using std::disclaimer;