Re: [xml] XPath fix

On Fri, Mar 22, 2002 at 12:23:39PM -0000, Cyberthymia wrote:
 Section 3.5 of the XPath spec states:
   "This is the same as the % operator in Java and ECMAScript."
   "This is not the same as the IEEE 754 remainder operation,
    which returns the remainder from a rounding division."

So they may be right, I hate those parts where XPath/XSLT relies on Java
for the semantic of operations, it is usually a mess.

That bit confused the heck out of me - so does that imply that Java doesn't
do IEEE 754 floating point numbers properly?
  seems to imply it, yes. You're surprized ?
I've found another couple of problems with float, round and ceil.
floor(-5.2) returns -5 instead of -6
ceiling(-5.2) returns -4 instead of -5
round(-5.6) returns -5 instead of -6
I've had a look at the code in xpath.c that does this maths
(xmlXPathFloorFunction(), etc) and what I thought would have been the
correct fix (by using the real C functions) in all 3 cases has been "#if
0"'d out and replaced by approximations doing wierd things with casts.
This is probably a silly question, but was there a specific issue caused by
using the C functions that stopped them from working?

  Looked at it, I wonder if I didn't do this to avoid using the
functions from the math library when avoidable. Weird casts are 
a sign of ownership ... it seems I forgot about negative values though :-)

  Apparently I got burned by a problem with floor() as a comment
indicates : "floor(0.999999999999) => 1.0 !!!!!!!!!!!"
and decided to bypass it using direct cast to implement the right

The enclosed patch tries to fix this, could you build a test file
like the others in test/XPath/expr/ testings those 3 functions and
raise errors if there is still some to fix,



Daniel Veillard      | Red Hat Network
veillard redhat com  | libxml GNOME XML XSLT toolkit | Rpmfind RPM search engine

Attachment: rounding.patch
Description: Text document

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