# Functions and Operators

The `fn:dateTime` function has been changed so that if either argument is an empty sequence, the result is an empty sequence. This implements a late change to the specification: see W3C bugzilla entry 3651.

The old `xdt` namespace is no longer supported. (The types previously in this namespace are now in the XML Schema namespace `http://www.w3.org/2001/XMLSchema`).

A new extension function `saxon:sort` has been introduced to allow sorting in free-standing XPath applications. There are two variants: a single argument version which simply sorts a sequence of nodes or atomic values on the value itself (after atomization in the case of a node), and a two-argument version whose second argument is an expression (obtained by calling saxon:expression()) that is used to calculate the sort key.

An enhancement to the `saxon:transform` extension function allows parameters to be supplied to the transformation. This is done by introducing an optional parameter whose value is a sequence of nodes (typically elements): the name of the node is used as the name of a parameter, and the atomized value of the node is used as the value of the parameter.

The Saxon-SA extension functions `saxon:index` and `saxon:find` have been rewritten to use the same indexing logic as is used for implicitly-created indexes. A consequence is that the order of results (which has never been well-defined) may be different from before.

The function `iri-to-uri()` now escapes ASCII characters that are disallowed in an IRI value, specifically the characters space, double-quotation-mark, less-than, greater-than, backslash, circumflex, grave accent, left curly brace, vertical bar, and right curly brace.

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