Runtime code reloading in D, part 1

[Dmitry Olshansky]

07-Jan-2013 00:02, Dmitry Olshansky пишет:
> 06-Jan-2013 23:55, Philippe Sigaud пишет:
>> On Sun, Jan 6, 2013 at 6:49 PM, Dmitry Olshansky <dmitry.olsh at gmail.com
>> <mailto:dmitry.olsh at gmail.com>> wrote:
>>
>>     Regarding toString there is a better signature that avoids useless
>>     allocations:
>>
>>     void toString(scope void delegate(const (char)[]) sink);
>>
>>     It takes a delegate to output string representation directly to the
>>     destination via 'sink' delegate (that may e.g. write chars to file).
>>     Plus the 'scope' part of declaration avoids allocating the said
>>     delegate on the heap.
>>
>>     I'd even say that string toString(); is an artifact of the past,
>>     instead to!string should be used (if allocating a string is fine).
>>
>>
>> I know you explained that already, but see, that again slipped my mind.
>> This toString(sink) thingy seems cool, but is there a documentation on
>> it somewhere? Without a related doc, I fear no one will know this exists.
>>
>
> Guess I need to find the original on toString and bit-blit it over with
> this new sink thingy ;)
>

There is a short note in object.d:
...
string toString();
		Convert Object to a human readable string.
...

That is any class may override it.

However the real relevant golden bit of information is buried after a 
row of formatValue templates (that hardly makes any sense to newcomers) 
at the bottom of std.format page:
(http://dlang.org/phobos/std_format.html)

Aggregates (struct, union, class, and interface) are basically formatted 
by calling toString.

toString should have one of the following signatures:
const void toString(scope void delegate(const(char)[]) sink, FormatSpec 
fmt);
const void toString(scope void delegate(const(char)[]) sink, string fmt);
const void toString(scope void delegate(const(char)[]) sink);
const string toString();


So it's quite flexible. Even better then I've been advertising it.
Note that classes are covered. I bet it can call virtual functions 
through base reference if base defines the new variation of toString.


The problem is if it's going to be extended to wchar/dchar... At least 
wchar is useful on Windows.

But the real fun is that I fail to find any real description of toString 
in the docs for d-p-l website!

The only files in d-p-l site where it is found in are:

- errors.dd:
... class Error has a pure virtual a function called toString() which 
produces a char[] with a human readable description of the error.)

Nothing useful and it's out of date! It returns a string (immutable) 
these days.

- lazy-evaluation.dd uses as an example of expensive computation and has 
the form of toString(i) where i is an int (wtf?!).

Probably horribly out of date as it should use either format or to!string.

- tempalte.dd uses std.string.toString as an example (same as in lazy?) 
and it's again an out of date piece of crap.

And a couple more files call it here and there (e.g. windows.dd to 
display exception message box).


-- 
Dmitry Olshansky