Using Michael Kay's book "XSLT 2.0 and XPath 2.0 4th Ed" as a reference on page 655 he says that the type constructor function is identical to the cast as with the ? option. A quote from his book says:
For example, the expression «@A cast as xs:integer?» can be rewritten as a function call, «xs:integer(@A)» ... if an empty sequence is supplied to a constructor function, it returns an empty sequence ... The only cases where you need to use the full «cast as» expression are: When you want to indicate that an empty sequence is not allowed.
Using Michael Kay's book "XSLT 2.0 and XPath 2.0 4th Ed" as a reference on page 655 he says that the type constructor function is identical to the
cast aswith the?option. A quote from his book says: