Re: How to build a string on the fly, using std::ostringstream?

>> Do you have any references, showing
>> that the "flush trick" is indeed a well-known idiom?

Tony replied:
> Well, I recall having first encountered it in a
> discussion in one of the clc++/clc++m newsgroups,
> presented by one of the regulars.  After a bit of
> searching, I've finally discovered that thread:
>
http://groups.google.co.uk/group/comp.lang.c++.moderated/browse_thread/thread/28f0226f8809eff5/

Thanks for the link to that "std::ostringstream misunderstanding" thread! 
I
hadn't read it yet!


> "Idiomatic" is certainly not a description of
> this technique and I retract my use of that term.
> "A curiosity" is probably nearer the mark.
....
>> (I wonder how many people actually /know/ that std::flush
>> is inserted by a member function [...] )

> Alf's original presentation of this method actually
> used the ostream::flush() member function (why didn't
> I remember it that way?), so knowledge of how
> std::flush() is inserted becomes moot.

Good point.  The thread also has a link to a relevant paragraph of a paper
by
Howard Hinnant, Dave Abrahams, and Peter Dimov:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2004/n1690.html#Use%20of%20Rvalue%20Streams
Which says:
   As a workaround, many people instead code:
     ...
     std::ofstream("Log file", std::ios::app).flush() << "Log message\n";
     ...
   The ".flush()" is a no-op that simply changes the rvalue ofstream
   into an lvalue.

So if many people do it like that, I guess you were right, and it /is/
idiomatic after all.  Or maybe we should call it "an idiomatic curiosity" 
;-)


Kind regards,

Niels


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