Re: [boost] Fixed-Point Decimal Type

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2001-05-09 18:27:09

On Wednesday, May 9, 2001, at 06:50  PM, John Max Skaller wrote:

>> Anyway, I'm hoping that standard C++ facilities (I/O streams,
>> I/O manipulators and locale facets) will be sufficient.
>
> 	They definitely aren't. They're enough for
> debugging, or printing a short 'You owe me $25.00!'.
> They may be enough for ticketing. They're completely
> useless for serious commercial reporting,
> _especially_ financial reports. These things have
> formatting rules which go well beyond the primitive
> features of IO streams: the number of options is
> quite large. for example, sometimes negative
> numbers are written with brackets:
>
> 	(234.75)

This can be handled by having a class derived from 
std::moneypunct<charT> return "()" from the virtual function 
do_negative_sign().

> and sometimes with a trailing minus
>
> 	234.75-

do_negative_sign() should return "-" and do_neg_format() should return a 
pattern with "sign" as the last element.

> and sometimes spaces are required:
>
> 	12 234.76

You mean as a thousands separator?  Have do_thousands_sep() return ' '.

> and sometimes commas:
>
> 	12,234.76

Have do_thousands_sep() return ','

> and sometimes a floating dollar sign:
>
> 	  $12.30
> 	 $222.70
>
> and sometimes a fixed position for the sign:
>
> 	$ 12.30
> 	$222.70

Set adjustfield to internal, set width appropriately, and put "none" in 
the pattern where you need to fill up space (and set the fill character 
if it isn't what you want already).

> and it goes on and on. ...<snip>...In any case, the right way to do IO 
> is to do formatting
> 'in-core', and output a string. So the facilities in
> iostreams are really for debugging, and nothing more.

I disagree.  The monetary formatting functionality in <locale> is fairly 
thorough and complete.  You haven't shown any examples here that the std 
monetary facets won't handle.

-Howard