Semantics of toString

[Andrei Alexandrescu]

Steven Schveighoffer wrote:
> On Tue, 10 Nov 2009 07:49:11 -0500, Justin Johansson <no at spam.com> 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.
>>>
>>> }
>>
>> That's starting to look like a "serialize" method!
> 
> As it should.  I should be able to print a 10000 element container 
> without having to load a string representation of 10000 elements in memory.
> 
> I'd also like to see the name toString changed to something more 
> appropriate, like output().
> 
> And although I think a direct translation is mostly possible, emulating 
> writefln string formatting from tango would be a burden.  I don't know 
> if there's any way around it without coming up with some complicated 
> "formatting provider" interface/object implementation, and I don't think 
> it's worth it.
> 
> Unfortunately, I doubt Walter accepts this, it's been proposed in the 
> past without success.
> 
> -Steve

Walter does not feel strongly about Phobos. The save() method in "On 
Iteration" intently makes it possible to define ranges as interfaces, 
which in turn should pave the way towards defining a coherent text 
streaming mechanism.	

Andrei