Re: [boost] Re: Re: is_nan

From: Gabriel Dos Reis (gdr_at_[hidden])
Date: 2003-07-13 03:21:40

"Paul A. Bristow" <boost_at_[hidden]> writes:

| I think this would be excellent (and overdue). It needs to support double and
| long double (and facilitate UDTs too if possible).
| 
| There is also the matter of signalling and quiet NaN. Although signalling NaN
| may cause an hardware exception if enabled, I suspect it is more useful if isnan
| returns ture for both types of NaN.

Agreed.  It is no question that isnan should distinguish between Quiet
NaNs and Signalling NaNs.  They are all NaNs.

|  At least we should make this clear.  I
| think this is what MSVC 7.1 does but the documentation is thin.
| 
| There is also a single IEEE FP pattern called 'indeterminate' or what Intel call
| 'NotAVal" (ox1fffe000...) which might become useful as a Portable Standard
| "missing value" marker if portably supported?

I won't take that road.  

Signalling NaNs are used to indicate missing initialization values.

| And can anyone help with allowing one to easily customise the display of NaNs?
| (and infs, max, min...?) I believe that a new (derived) num_put facet is the way
| to do this.  Does anyone have an actual implementation of this to contribute
| too?

I'm willing to volunteer but I'm not sure I really understand the
question. Can you elaborate a little bit?

-- Gaby