XPath/XSLT and extended precision

[Vincent Lefevre]

Hello,

The XPath 1.0 recommendation says:

A number represents a floating-point number. A number can have any
double-precision 64-bit format IEEE 754 value [IEEE 754]. These
include a special "Not-a-Number" (NaN) value, positive and negative
infinity, and positive and negative zero. See Section 4.2.3 of [JLS]
for a summary of the key rules of the IEEE 754 standard.

It doesn't say many things concerning the operations, but it seems that
it also requires them to conform to the IEEE-754 standard (as this is
the case for the division: "The div operator performs floating-point
division according to IEEE 754.").

Now my question: is extended precision allowed as the "destination"
format (where "destination" is defined in the IEEE-754 standard)?
i.e. computations would be performed with exact rounding to extended
precision, then rounded to double precision (hence the results would
be rounded twice).

This is what happens with xsltproc (libxslt) on x86 processors:

<?xml version="1.0"?>

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:output method="text" indent="no"/>

<xsl:template match="/">
<xsl:choose>
<xsl:when test="9007199254740992 + 1.00001 = 9007199254740992">
<xsl:text>equal</xsl:text>
</xsl:when>
<xsl:otherwise>
<xsl:text>different</xsl:text>
</xsl:otherwise>
</xsl:choose>
<xsl:text> </xsl:text>
</xsl:template>

</xsl:stylesheet>

On an x86, the output is "equal", whereas on a PowerPC, it is
"different". So, is it a bug in libxslt or is it allowed by the
XPath recommendation?

--
Vincent Lefèvre <vi*****@vinc17.org> - Web: <http://www.vinc17.org/> - 100%
validated (X)HTML - Acorn Risc PC, Yellow Pig 17, Championnat International
des Jeux Mathématiques et Logiques, TETRHEX, etc.
Work: CR INRIA - computer arithmetic / SPACES project at LORIA

[Dimitre Novatchev]

> This is what happens with xsltproc (libxslt) on x86 processors:

<?xml version="1.0"?>

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:output method="text" indent="no"/>

<xsl:template match="/">
<xsl:choose>
<xsl:when test="9007199254740992 + 1.00001 = 9007199254740992">
<xsl:text>equal</xsl:text>
</xsl:when>
<xsl:otherwise>
<xsl:text>different</xsl:text>
</xsl:otherwise>
</xsl:choose>
<xsl:text> </xsl:text>
</xsl:template>

</xsl:stylesheet>

On an x86, the output is "equal", whereas on a PowerPC, it is
"different". So, is it a bug in libxslt or is it allowed by the
XPath recommendation?

I cannot reproduce your problem. xsltProc gives me: "different" on my
Pentium 4.

=====
Cheers,

Dimitre Novatchev.
http://fxsl.sourceforge.net/ -- the home of FXSL

[Vincent Lefevre]

In article <bi************@ID-152440.news.uni-berlin.de>,
Dimitre Novatchev <dn********@yahoo.com> wrote:

I cannot reproduce your problem. xsltProc gives me: "different" on my
Pentium 4.

Perhaps a different version for which the problem was fixed?
Here's mine:

greux:~> xsltproc --version
Using libxml 20508, libxslt 10030 and libexslt 720
xsltproc was compiled against libxml 20507, libxslt 10030 and libexslt 720
libxslt 10030 was compiled against libxml 20507
libexslt 720 was compiled against libxml 20507

FYI, this is the latest version of the Debian package (sid).

--
Vincent Lefèvre <vi*****@vinc17.org> - Web: <http://www.vinc17.org/> - 100%
validated (X)HTML - Acorn Risc PC, Yellow Pig 17, Championnat International
des Jeux Mathématiques et Logiques, TETRHEX, etc.
Work: CR INRIA - computer arithmetic / SPACES project at LORIA

[Dimitre Novatchev]

Mine is:

Using libxml 20504, libxslt 10027 and libexslt 718
xsltproc was compiled against libxml 20504, libxslt 10027 and libexslt 718
libxslt 10027 was compiled against libxml 20504
libexslt 718 was compiled against libxml 20504

=====
Cheers,

Dimitre Novatchev.
http://fxsl.sourceforge.net/ -- the home of FXSL
"Vincent Lefevre" <vi**********@vinc17.org> wrote in message
news:20*****************@vinc17.org...

In article <bi************@ID-152440.news.uni-berlin.de>,
Dimitre Novatchev <dn********@yahoo.com> wrote:

I cannot reproduce your problem. xsltProc gives me: "different" on my
Pentium 4.
Perhaps a different version for which the problem was fixed?
Here's mine:

greux:~> xsltproc --version
Using libxml 20508, libxslt 10030 and libexslt 720
xsltproc was compiled against libxml 20507, libxslt 10030 and libexslt 720
libxslt 10030 was compiled against libxml 20507
libexslt 720 was compiled against libxml 20507

FYI, this is the latest version of the Debian package (sid).

--
Vincent Lefèvre <vi*****@vinc17.org> - Web: <http://www.vinc17.org/> -

100% validated (X)HTML - Acorn Risc PC, Yellow Pig 17, Championnat International des Jeux Mathématiques et Logiques, TETRHEX, etc.
Work: CR INRIA - computer arithmetic / SPACES project at LORIA

[Vincent Lefevre]

In article <bi************@ID-152440.news.uni-berlin.de>,
Dimitre Novatchev <dn********@yahoo.com> wrote:

Mine is: Using libxml 20504, libxslt 10027 and libexslt 718
xsltproc was compiled against libxml 20504, libxslt 10027 and libexslt 718
libxslt 10027 was compiled against libxml 20504
libexslt 718 was compiled against libxml 20504

Older than mine. So, I've filled a bug on the Debian BTS, in case this
is a Debian(/unstable)-only bug.

--
Vincent Lefèvre <vi*****@vinc17.org> - Web: <http://www.vinc17.org/> - 100%
validated (X)HTML - Acorn Risc PC, Yellow Pig 17, Championnat International
des Jeux Mathématiques et Logiques, TETRHEX, etc.
Work: CR INRIA - computer arithmetic / SPACES project at LORIA