Re: [boost] [lexical_cast] char types and UDTs

Subject: Re: [boost] [lexical_cast] char types and UDTs
From: Olaf van der Spek (ml_at_[hidden])
Date: 2012-04-11 12:36:34

On Wed, Apr 11, 2012 at 5:18 PM, Eric Niebler <eric_at_[hidden]> wrote:
>> You have to construct a string somewhere, don't you?
>> If you have one already, you could use iterator_range<const char*>
>> instead to avoid a copy.
>
> Yes, I see that lexical_cast has optimizations for
> iterator_range<wchar_t const *> and a few other, sufficiently
> 'string-like' types. But sub_match essentially *is* a string-like
> iterator_range. (It's a std::pair of iterators.) I'm genuinely surprised

Is it? Does it have begin() and end() for example?
Why not use std::iterator_range instead of std::pair?

> there's no way to tell lexical_cast that. Instead I have to just know
> (a) which are the magical types lexical_cast is optimized for and (b)
> for which it can determine the correct underlying stream character type
> (hint: the docs are unclear or out of date), and massage my type into
> one of those before calling lexical_cast. Why?

How could it automatically determine the necessary character type?

Olaf