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Re: NaN and Infinity in format-number
Subject: Re: NaN and Infinity in format-number|
From: Jack Matheson <jack@xxxxxxxxxxxxxx>
Date: Fri, 13 Jan 2006 11:59:42 -0600
Thanks again for the great explanation!
In the following stylesheet:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/
1: <xsl:value-of select="format-number(0.0 div 0.0, '(#)')"/>
2: <xsl:value-of select="format-number(1.0 div 0.0, '(#)')"/>
...I see interesting results in Saxon 6 and Xalan 2.6:
I was expecting either parenthesis around both values or no
parenthesis at all. Is this a result of the XSLT 1.0
DecimalFormat in the JDK?
Yes, almost certainly.
Is this the conforming XSLT 1.0 behavior?
XSLT 1.0 defines the spec in terms of the JDK 1.1.8 specification
DecimalFormat. This is a pretty shoddy spec, as it happens. It says:
* NaN is formatted as a single character, typically \\uFFFD.
* +/-Infinity is formatted as a single character, typically \
the positive and negative pre/suffixes.
The "single character" is nonsense (though it's still there in the
spec): DecimalFormatSymbols allows a String for these symbols! But
it's clearly a string.
But yes (to my surprise), it does seem to be an explicit part of
that the prefix/suffix are included for Infinity, but not for NaN. My
surprise is because there are so many other aspects of the behavior
aren't defined in any detail in the 1.1.8 spec, although in some
have been defined more carefully in subsequent versions.
There's one notorious oddity: the JDK 1.1.8 implementation ignores
the negative subpattern, except for the prefix and suffix, but
nothing in the spec to suggest this. In subsequent versions of the
behavior was documented.
I noticed Saxon 8 puts parenthesis around both values. Is this an an
XSLT 2.0 action?
Yes. The XSLT 2.0 spec has cut loose from the original dependency
on the JDK
documentation, and now contains a self-contained definition of the
See http://www.w3.org/TR/xslt20/#formatting-the-number. Rule 1 says
the value is NaN, it is output using the prefix and suffix from the
I hadn't actually noticed that this was an incompatibility from
behavior. I'll raise it as a comment on the spec for the WG to review.
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