RE: An empty sequence is not allowed as the first arg

You've got two choices. Either write your function so it can handle an empty
sequence, or don't call it with an empty sequence. One way of doing the
latter is to include string(.....) in the function call - the string()
function never returns an empty sequence.

Michael Kay
http://www.saxonica.com/ 

> -----Original Message-----
> From: cknell@xxxxxxxxxx [mailto:cknell@xxxxxxxxxx] 
> Sent: 02 June 2006 21:02
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject:  An empty sequence is not allowed as the first 
> argument ...
> 
> I've written an XSLT function to format dates fetched from a 
> database. This worked well until I pulled some records with 
> NULL values for the date I wished to format. When my 
> stylesheet encountered this element, Saxon emitted this error 
> message and ended with a fatal error:
> 
> Fatal Error! An empty sequence is not allowed as the first 
> argument of ck:std-date-string-fmt()
> 
> You may well ask, "What did you expect?" The answer is that I 
> was not expecting anything. I was happily ignorant of the 
> lurking danger. I tried to supply a default empty string 
> value for the parameter that causes the function to choke 
> when no value is supplied, only to be upbraided by Saxon 
> telling me that default values are not permitted in function 
> parameters.
> 
> (I had slipped in an xsl:choose to catch the empty-sting 
> cases, but without being able to assign a default value, that failed.)
> 
> Does an empty sequence have some kind of xs:type that I could 
> cast to an xs:string, and if so, how is it done? If not, how 
> do I handle cases when no data comes from my database?
> --
> Charles Knell
> cknell@xxxxxxxxxx - email