Why does toString() exist? It seems useless.

[JAnderson]

Don wrote:
> I cannot understand the rationale for a toString() member function which 
> doesn't support formatting.
> 
> I don't think I've ever made a class which only has a single format 
> option. If the class contains any integers, I want to specify whether it 
> should use hex or decimal, leading zeros, sign. If it contains floating 
> point numbers, it's number of digits, scientific notation, hex or 
> decimal, and what to do with NaNs. And of course there are locales.
> 
> Seriously, I cannot remember ever not having this requirement, so I 
> cannot imagine a use for toString().
> 
> C++ got around this by giving state to the iostream classes. As far as I 
> can tell, neither Phobos nor Tango provide any support at all.
> 
> Practical example: BigInt (which I'm developing in both Tango and 
> Phobos). It is a struct. How can it support I/O? I can't work out how to 
> do it in either library.

I think you can do much the same as iostream and still take advantage of 
toString.  Something like:

string foo = a.toString() ~ format(a, "...");

Where format would be special overloaded template (with specialization) 
that does conversions.

-Joel