Re: [XSL 3.0] Function that check if a xs:string can b

Hello,

As an academic exercise it is still interesting to ponder what might be done
without 'castable as'.

I think it was Ken H who once suggested (context of XSLT 1.0)
select="number($str) = number($str)" as NaN is not equal to itself. I can't
say where he got it. (In XPath 1.0 one was forced to be creative.) Or whether
it would work for you in the given context or indeed corresponds to 'castable
as'.

Regards, Wendell


-----Original Message-----
From: John Lumley john@xxxxxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Sent: Wednesday, May 31, 2023 10:09 AM
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re:  [XSL 3.0] Function that check if a xs:string can be
converted as a xs:double

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