[xquery-talk] Literal NaN

David Lee dlee at calldei.com
Fri Feb 25 10:29:11 PST 2011

Today I ran into yet a new hole in my xquery knowledge.  (I guess I'm a
sponge !)


I needed to check if a value was numeric or not.  I found the functx





The code is interesting :


define function is-a-number 

  ( $value as xdt:anyAtomicType? )  as xs:boolean {


   fn:string(fn:number($value)) != 'NaN'




I'm wondering why this hand-standing ? Why cant I compare to NaN directly ?

Is there no literal constructor for NaN ? I cant find any . and my obvious
attempts fail like


                If(  number("abc") eq NaN ) . 


Its just strange to me to have a value which can be returned by a function
which you cant construct .

Or have to use conversion to string , or maybe something equally obtuse


                number("NaN") eq number( non-numeric-value )







David A. Lee

 <mailto:dlee at calldei.com> dlee at calldei.com

 <http://www.xmlsh.org> http://www.xmlsh.org


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