Re: metatables for strings?

[Andrew Starks <andrew.starks@...>]

On Sunday, May 3, 2015, Nagaev Boris <bnagaev@gmail.com> wrote:
> On Sun, May 3, 2015 at 5:06 PM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> > 2015-05-03 18:40 GMT+02:00 Nagaev Boris <bnagaev@gmail.com>:
> >> On Sun, May 3, 2015 at 4:35 PM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> >>>
> >>> You can put a function in the "string" table and it will immediately
> >>> be callable with object-oriented syntax on a string object just like
> >>> str:format etc. Since the first argument is provided, that function
> >>> can itself pick out a submethod from a table of functions.
> >>>
> >>
> >> Changing global metatable of all strings does not sound good. If all
> >> strings had same methods, then methods added to UrlString, would also
> >> be available to normal strings. It is confusing and it breaks idea of
> >> sandboxes, because sandboxed code can apply UrlString's methods to
> >> malicious strings.
> >
> > If the methods were all provided by the sandbox author, who presumably
> > knows what he is doing, I don't see the problem.
> >
>
> Can a sandbox isolate added string's methods? Can you provide
> sandboxing function passing this test:
>
> string.hack = function() print("Hacked") end
> code = [[ ("just string"):hack() ]]
> sandbox(code)
>
>
> --
>
>
> Best regards,
> Boris Nagaev

Also, you can use the debug library to discover the caller's environment and then call the methods found in the "strings" library of that _ENV or yours, if that table is absent. 

So I believe that what you want is achievable, in the sort of tar-pit-like way that happens when you can't yet / quite re-imagine your problem to fit the language.  :)

-Andrew