RE: Representation of floating point values.

We're both right: Java appears to use option 3 for compile-time literals,
option 2 for the Double.parseDouble() method (string to double conversion).

Michael Kay
 

> -----Original Message-----
> From: Daniel Engovatov [mailto:dengovatov@bea.com] 
> Sent: 07 March 2005 22:23
> To: Michael Kay; www-xml-schema-comments@w3.org
> Cc: w3c-xml-query-wg@w3.org
> Subject: RE: Representation of floating point values.
> 
> 
> >Of the three possible options:
> 
> >1. Map to the largest finite double
> >2. Map to +Infinity
> >3. Raise an error
> 
> >option 1 seems the least desirable.
> 
> >Java does (2).
> 
> 
> According to 
> 
> http://java.sun.com/docs/books/jls/second_edition/html/lexical
> .doc.html#
> 230798
>  
> Java uses option 3, doesn't it?  Quote:
> 
> " A compile-time error occurs if a nonzero floating-point 
> literal is too
> large, so that on rounded conversion to its internal representation it
> becomes an IEEE 754 infinity. A program can represent 
> infinities without
> producing a compile-time error by using constant expressions such as
> 1f/0f or -1d/0d or by using the predefined constants POSITIVE_INFINITY
> and NEGATIVE_INFINITY of the classes Float and Double."
> 
> Actually, this document has the same bug, as a "rounded 
> conversion" can
> not be infinity.
> 
> I would imagine that raising an error (not a valid 
> representation of an 
> Floating point literal) is the most desirable outcome.  If somebody
> wanted an INF, there are explicit way to construct it.
> 
> Daniel;
> 
>  
> 
> > -----Original Message-----
> > From: w3c-xml-query-wg-request@w3.org 
> > [mailto:w3c-xml-query-wg-request@w3.org] On Behalf Of 
> Daniel Engovatov
> > Sent: 07 March 2005 21:43
> > To: www-xml-schema-comments@w3.org
> > Cc: w3c-xml-query-wg@w3.org
> > Subject: Representation of floating point values.
> > 
> > 
> > During our recent XQuery working group meeting we have 
> closed an issue
> > regarding what should be done if a numerical literal representing a
> > float or double value is out of range for IEEE 754 values 
> > (positive and
> > negative overflow or underflow).
> > 
> > --------
> > RESOLUTION: Too big float/double values.
> > 
> http://lists.w3.org/Archives/Member/w3c-xml-query-wg/2005Feb/0084.html
> > is rejected. No action required to 3.1.1. Schema says that 
> one should
> > map to the largest float or double value.
> > --------
> > 
> > It does seem to me that this is an unfortunate choice in 
> the Schema to
> > just map a non-representable number into another number.  Probably,
> > other options should be allowed for an implementation, such 
> raising an
> > error and mapping to +/- INF.
> > 
> > Sincerely,
> > 
> > Daniel Engovatov.   
> > 
> > 
> > 
> > 
> 
> 
> 
> 
> 
>

Received on Monday, 7 March 2005 22:38:08 UTC