xf:index-of

I tried following xquery on Tamino Interactive Interface, but it gives the error saying that the function is unknown. What did I do wrong?

declare namespace xf=“http://www.w3.org/2002/08/xquery-functions
let $b := (1,2,3)
return xf:index-of($b,1)

It seems all the functions on sequences are not working. Can someone tell me why? thanks.

All of the functions documented in the Tamino documentation appear to be working. “index-of” is not documented there, so I presume it is not supported.

You can retrieve a specific node of a sequence with something like this:

let $b := (1,2,3)
return $b[position()=2]