Re: [boost] Heads up - string_ref landing

Subject: Re: [boost] Heads up - string_ref landing
From: Rob Stewart (robertstewart_at_[hidden])
Date: 2012-12-12 10:49:34

On Dec 12, 2012, at 8:21 AM, Yakov Galka <ybungalobill_at_[hidden]> wrote:

> On Wed, Dec 12, 2012 at 2:55 PM, Rob Stewart <robertstewart_at_[hidden]>wrote:
> 
>> On Dec 12, 2012, at 2:38 AM, Yakov Galka <ybungalobill_at_[hidden]> wrote:
>> 
>>> On Tue, Dec 11, 2012 at 11:47 PM, Rob Stewart <robertstewart_at_[hidden]
>>> wrote:
>>> 
>>>> On Dec 10, 2012, at 7:55 AM, Sergey Cheban <s.cheban_at_[hidden]> wrote:
>>>> 
>>>>> On 09.12.2012 17:13, 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.
>>> 
>>> Would it mean !empty() or !!begin()?
>> 
>> The former certainly. string_ref's are never assumed to be null terminated (which is why I provide data() and not c_str()), so the latter is not
>> sensible.
> 
> I wrote !!begin(), not !!*begin(). In other works string_ref can *actually be a null pointer*, or at least I haven't seen anyone saying the contrary.

Of course. I misread your intent. You're assuming that the iterator type is a pointer. Besides, if string_ref holds a null pointer, I'd expect empty() to return true. Thus, the operator, and empty(), always mean a string with no characters.

>>> The std::string has no such operator.
>>>> 
>>>> Why does that matter? It's still convenient. It would be a nice addition to std::string.
>>> 
>>> std::string does not have a 'null' state.
>> 
>> It's the state represented by empty().
> 
> I am not sure it is so certainly accepted by all.

It is the logical interpretation. It indicates whether the string is non-empty. I don't see any other generally useful interpretation, do you?

___
Rob