Re: [boost] Re: Formal review of "Output Formatters" library beginstoday

From: John Torjo (john.lists_at_[hidden])
Date: 2004-09-13 03:05:32

>>
>> Well, I think my alternative is better if you want a stateful change,
>> since yours doesn't accomplish that.  My suggestion is certainly
>> consistent with normal io manipulators.  The point is to stream a
>> bunch of sequences without having to repeat the format part.
> 
> 
> I understand what you are saying and yes your version is neater. 
> However, implementing something like this would have performance 
> penalties (because you will need to create/store the preset values at 
> run-time).

The penalties are small. Anyway, using std::istream/ostream have 
penalties, compared to using raw FILEs ;)

That said, in this case there shouldn't be many penalties.
Again, you can use
ios_base::pword and ios_base::iword for this.
It's an advanced technique, but I think it can prove very neat and flexible.

> 
> It will also change the way all sequence constructs are rendered. (n-ary 
> types have a different rendreing so won't be affected). As I understand, 
> this is the desired effect. But then:

You can make it possible to associate a fmt object with a delimeter object.

Example: pairfmt() with openclose_formatter.
basicfmt() with formatter. Etc.

Then, you can store (default) delimeter objects within the stream.
Once you want to output/input something, it requires a specific delim 
object. You'll somehow use ios_base::pword/iword to get a reference to 
that object.

> [3] how do you extend this to formatter types that have additional 
> delimeters?
see above.

> [4] how do you know when to extract the default delimeter values from 
> the stream?
> 
see above.

Best,
John

-- 
John Torjo
-- john_at_[hidden]
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