Re: [xsl] [XSL 3.0] Function that check if a xs:string can be converted as a xs:double

["John Lumley john@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

On 31/05/2023 13:13, Christophe Marchand cmarchand@xxxxxxxxxxxxxx wrote:
> I've also found xs:boolean(number($s)) is working correctly.

I would strongly suggest that you use the $s castable as xs:double 
construct rather than this one.

As has been pointed out it fails for s="0", as the boolean value of a 
zero is false. But you've also been somewhat misled by getting correct 
answers with e.g.s="A string".

The definition of number() 
(https://www.w3.org/TR/xpath-functions-31/#func-number) shows that when 
supplied with a string which cannot be parsed as a number, in most 
circumstances rather than failing, it returns NaN (not a number), whose 
boolean value is then taken as false.

When you wish to check whether something can be cast to a given type 
using the castable as operator 
(https://www.w3.org/TR/xpath-31/#id-castable) is much preferable, and 
much clearer.


John Lumley