Re: [boost] Review request : format

From: Beman Dawes (bdawes_at_[hidden])
Date: 2001-12-20 10:57:26

At 03:48 AM 12/20/2001, Samuel Krempp wrote:

 >On Thu, 2001-12-20 at 02:52, Karl Nelson wrote:
 >
 >> If you want to force rules of presidence use what is given for
 >> that...
 >>
 >>    cout << (format(str) << 1 << 2) << endl;
 >>
 >> The class could be designed to handle that.
 >
 >It could, but then in those cases it would act like a string-maker, not
 >a manipulator.
 >(inside the parenthesis, format doesn't know about cout's state. So it
 >does its formatting, and then dump a string at the end. There is no way
 >to stack the arguments and wait until you get cout, before formatting
 >them)
 >So format would have a different behaviour there, and it would not be
 >apparent.
 >So all in all, I guess you would not make the class handle that, unless
 >it always act like a string-maker like mine.
 >
 >In fact, I realised you use operator<< because you aim at making format
 >pretty much like a manipulator.
 >while my class is a string maker , for which operator<<(stream, format)
 >is define to facilitate the use inside stream output chains.
 >
 >that's the heart of the issue..
 >In my experiments, it seemed to me it wasn't possible to make the format
 >objects act like a manipulators in all aspects, I'd always get a dirty
 >aspect sooner or later. I'll try to recall the details for this evening,
 >to debate whether we should stick to a simple string-maker or aim for a
 >'stream manipulator' approach.  This choice governs the choice between
 ><< and %.

Because the "manipulator-like" approach looks so familiar, and the 
"string-maker" approach looks strange at first, that in of itself is an 
argument for the manipulator-like approach.

Of course if it turns out there are other killer arguments in favor of the 
string-maker approach, you should choose string-maker.

But if it is even close to a toss-up, consider that the manipulator 
approach many be easier to teach, easier to learn, and be viewed as the 
more mainstream approach.  I worry that we will all waste endless time 
explaining why string-maker was chosen over manipulator.

Whichever you choose, please carefully document the rationale!

--Beman