Boost logo

Boost :

Subject: Re: [boost] Heads up - string_ref landing
From: Sergey Cheban (s.cheban_at_[hidden])
Date: 2012-12-12 09:05:02

On 12.12.2012 1:47, Rob Stewart wrote:

>>>>> - safe bool or explicit bool conversion operator
>>>> I don't think this is a good idea.
>>> Why not?
>> This seems to be not intuitive and not so safe.
> It is quite intuitive to me. true means non-null, and false means null.
If the basic_substring<T> was convertible to bool, it would be used to
compare basic_substring<char> with basic_substring<wchar_t> (with
meaningless results).

>> The std::string has no such operator.
> Why does that matter? It's still convenient. It would be a nice addition to std::string.
I think that the substring class should be consistent with the existing
standard string interface. If you think that the operator bool is a good
addition to the [sub]string you may propose it to the standard commitee.

>>>> What about pop_back(), pop_front(), swap()?
>>> string_ref isn't a container, so pop_back() and pop_front() are inappropriate. However, back(), front(), and swap() are reasonable.
>> It is not a container (i.e., it does not own the content) but pop_* methods still may remove the characters from it.
> They wouldn't remove characters, they would only "forget" them. The semantic is sufficiently different that I don't think I would find them intuitive.
What is the difference? The substring does not own the characters anyway.

>> Btw, there also are [r]find*(), r[c]begin()/r[c]end() and compare() groups of methods in the std::basic_string.
> I don't think of string_ref as so complete an analogue to string. I see such things as the purview of a substring class, though that's purely subjective.
Why not? For example, it may be used as a key in some temporary std::map.

>>>> And again, I propose "substring" instead of "string_ref".
>>> I also have [const_]substring classes which have a different interface, so I disagree. (There is, of course, some overlap.)
>> 1. Are these classes in the Boost library and/or namespace?
> No. They are my own classes which I've not proposed to Boost.
I respect your needs but I don't think that it is a good idea for the
Boost library to avoid using convenient names just because these names
are used by somebody who uses the boost namespace implicitly.

>> 2. Do these classes do a different job, or they just have a different interface?
> They reference a std::string and operate on a subset of the string's characters. The have special constructors and replicate most of string's interface.
It seems that you may just switch to the boost::substring and get rid of
your substring implementation some day.

Sergey Cheban

Boost list run by bdawes at, gregod at, cpdaniel at, john at