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Subject: Re: [boost] [string] proposal
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2011-01-24 08:48:23

Dean Michael Berris wrote:
> Consider the following:
> template <class String>
> void needs_utf8(String const & s) {
> view<utf8_encoded> utf8_string(s);
> if (!valid(utf8_string))
> throw invalid_string("I need a UTF-8 string.");
> }
> template <class String>
> void needs_utf16(String const & s) {
> view<utf16_encoded> utf16_string(s);
> if (!valid(utf16_string))
> throw invalid_string("I need a UTF-16 string.");
> }
> I would say you have four choices when implementing `view`
> and `valid`:
> 1. view converts, and valid is a no-op.
> 2. view doesn't convert, and valid does the validation on the
> underlying string.
> 3. view converts, and valid does the validation on the
> underlying string.
> 4. view doesn't convert, but valid checks the validation on the view.
> I'm leaning towards #2.

#1 and #3 would be wasteful for cases when the string is already known to have the desired encoding, so they are non-starters.

I'm not sure I understand the distinction or reason for the distinction you imply by #2 versus #4. #2's wording suggests that you mean valid() accesses the underlying string through the view, but why is that better or worse than just using the view as in #4?

Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP

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