[xquery-talk] Literal NaN

[David Lee]

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
function

 

http://www.xqueryfunctions.com/xq/functx_is-a-number.html

 

 

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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