toString, to!(char[]) & co

[Fawzi Mohamed]

Taking a hint from bearophile I repost here some of my thoughts about 
converting to string.

If you look at the allocations needed for a toString, one sees the 
allocation of a lot of small strings, alloacation for the concatenation 
of a couple of the small strings, then again for the larger blocks 
until you get the final string.
To me it reeks of bad design, especially if there is an easy way to 
avoid most problems, a way that can avoid almost all allocations.

I find it much better to base everything on something like
	void writeOut(T,S...)(void delegate char[]sink, T object,S formatting)
that outputs to a sink, so that you can have output without memory
allocation.
(well my version is little more complex because I want to accept also
other stuff not just a sink 
http://github.com/fawzi/blip/blob/master/blip/io/BasicIO.d
  )

If you want a single string you can easily write helpers like
	T[] collectAppender(T)(void delegate(void delegate(T[]))
appender,char[] buf=null)
or similar ( 
http://github.com/fawzi/blip/blob/master/blip/container/GrowableArray.d
  ) that convert sink based stuff to a single string.

I think that that design is very efficient and clean, well I have to
admit that I *hate* toString and methods that convert stuff to string,
because they are unnecessarily inefficient, and can be trivially 
obtained from the more efficient ones.

Real serialization is a different beast (at least what I want
from serialization), there the "how" should be in the target serializer,
the serialization function should just give enough information to the
serializer, so that it might serialize how it pleases to him (in
particular meaningful labels should be given for serialization to
json,xml,...), at least that is what I do in my serialization library.

Fawzi