RE: [xsl] rounding within the "format-number" function

Subject: RE: [xsl] rounding within the "format-number" function
From: "Michael Kay" <mike@xxxxxxxxxxxx>
Date: Thu, 26 Jan 2006 16:50:28 -0000
> What I have noticed is that the XSL  "format-number" function 
>  rounds to
> the nearest even number, instead of the bigger one, as is usual and
> would be expected.  According to one site, this is sometimes called
> "banker's rounding." 
> Its purpose is to eliminate the slight bias that occurs when always
> rounding upwards.
> I am using XSLT 1.0.

Technically I don't think that XSLT 1.0 defines the rounding algorithm. It
defines format-number() in terms of the JDK 1.1 specification, and the JDK
1.1 specification didn't actually say what the rounding rules were. XSLT
implementations written in Java probably used the underlying JDK class
library, which did "banker's rounding", but implementations in other
languages might have used a different algorithm. XSLT 2.0 defines the rules
as you describe.
> On our pages, we want to always round up to two decimal places, and I
> don't want to lose the formatting. I would  want 9.2850 to round up to
> 9.29.   The solution that I have come up with is: 
> <xsl:value-of select='format-number( round(100*$number) div 100 ,
> "##.00" )'  
> Do you have a better solution?? Is there anyway to globally change the
> default rounding (banker's rounding) to always round up???

No, and no. (Not even in 2.0!)

Michael Kay

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