Semantics of toString

[Steven Schveighoffer]

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