Semantics of toString

[Denis Koroskin]

On Wed, 11 Nov 2009 04:27:45 +0300, Andrei Alexandrescu  
<SeeWebsiteForEmail at erdani.org> wrote:

> Bill Baxter wrote:
>> 2009/11/10 Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org>:
>>> Denis Koroskin wrote:
>>>> On Wed, 11 Nov 2009 02:49:54 +0300, Andrei Alexandrescu
>>>> <SeeWebsiteForEmail at erdani.org> wrote:
>>>>
>>>>> Don wrote:
>>>>>> Lutger wrote:
>>>>>>> Don wrote:
>>>>>>> ...
>>>>>>>> There is a definite use for such as thing. But the existing  
>>>>>>>> toString()
>>>>>>>> is much, much worse than useless. People think you can do  
>>>>>>>> something
>>>>>>>> with
>>>>>>>> it, but you can't.
>>>>>>>> eg, people have asked for BigInt to support toString(). That is an
>>>>>>>> over-my-dead-body.
>>>>>>> Since you are in the know and probably the biggest toString() hater
>>>>>>> around: are there plans (or rejections thereof) to change  
>>>>>>> toString() before
>>>>>>> D2 turns gold? Seems to me it could break quite some code.
>>>>>>  I'm hoping someone will come up with a design.
>>>>>>  Straw man:
>>>>>>  void toString(void delegate(const(char)[]) sink, string fmt) {
>>>>>>  // fmt holds the format string from writefln/formatln.
>>>>>> // call sink() to print partial results.
>>>>>>  }
>>>>> I think the best option for toString is to take an output range and  
>>>>> write
>>>>> to it. (The sink is a simplified range.)
>>>>>
>>>>> Andrei
>>>> It means toString() must be either a template, or accept an abstract
>>>> InputRange interface?
>>> It should take an interface.
>>  So yet another type in object.d?
>> Or require users in import something specific in every module that's
>> going to use toString?
>>  --bb
>
> I am not sure. Opinions as always are welcome.
>
> Andrei

Some ranges may be polymorphic, so having base interface hierarchy in  
Phobos would be useful anyway.

BTW, save() is already implemented and used throughout the Phobos under a  
different name - opSlice (i.e. auto copy = range[]). It's a bikeshed  
discussion, but why save() and not opSlice(), or even clone()?