At 2006-05-15 12:30 +0200, David Landwehr wrote:
It might be that a default of rounding the number expression isn't
always the solution an author would want. The reason I took a guess
for rounding is that if you write select="element[(((7 div 5) div 3)
* 5) * 3]", you get from the constant expression
select="element[6.99999999999]" which will never select an element.
In that particular case rounding would be what I expected.
Yes, I understood that, and it seems intuitive but from a standards
perspective the question would be would you want that to *always*
happen, or should it be up to the user to decide what to do with
inaccurate results as it might depend on the situation (as I tried to
highlight in my example)?
Thanks for following up.
. . . . . . . . . Ken
Best regards,
David
G. Ken Holman wrote:
At 2006-05-15 11:19 +0200, David Landwehr wrote:
Reading XPath 1.0 it states that a predicate evaluating to a
number will return true if equal to the proximity position of the
current node. I was wondering if there is a reason the evaluated
number isn't rounded by the XPath engine? Because XPath is based
on IEEE 754 the result of an evaluation might be inaccurate on the
last digit which will cause a predicate to return false where it
should return true. I'm just asking this out of curiosity and
accepts that an author has to call the round function if she uses
arithmetic which can give inaccurate results.
As the typical use is merely ordinal position in a node set I've
never had to worry about this in a predicate ... but I did have to
think about position() and rounding in a standalone <xsl:if> when
doing a two-column display in XSL-FO and I wanted to introduce a
column break in a standalone block ... I might have wanted to use
floor() instead of round() in the following:
<xsl:if test="position()=round(last() div 2)">
<block break-before="column"/>
</xsl:if>
... but I cannot readily extrapolate that into an XPath predicate.
I think you summarized correctly that if the author is doing things
that might give inaccurate results they should do it explicitly ...
as in my case they might want to make the decision between floor()
and ceiling() but in a predicate rather than just round(), so I
don't believe it makes sense to just implement round() by default.
I hope this helps.
. . . . . . . . . Ken
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