New features in XPath 3.0

Some of the new features in XPath 3.0 are as follows. For full details, see the W3C specifications.

The concatenation operator || is available (as in SQL). For example, ('$' || 12.5) returns the string '$12.5'.
A new simple mapping operator is available, !. This works rather like /, except there is no restriction that the left hand operand must be a node-set, and there is no sorting of results into document order. For example, (1 to 7)!(.*.) returns the sequence (1, 4, 9, 16, 25, 36, 49).
Local variables can be declared in a let expression, for example let $x := /*/@version return //e[@version = $x]
Inline function items can be declared, and used as arguments to higher-order functions. For example map(//employee, function($e){$e/salary + $e/bonus}). A function item is a third kind of item, alongside nodes and atomic values. The function represented by a function item $f can be invoked using a dynamic function call $f(args).
Maps are available (for more details see Maps. They provide a similar capability to "objects" in Javascript, or "associative arrays" in some other languages. But as befits a function language like XPath, they are immutable. A collection of functions is available to operate on maps (see ), and in addition there is new syntax for a map constructor (of the form map{ key := value, key := value } where both the keys and values are arbitrary expressions. There is a sequenceType for maps: map(K, V) defining the types of the key and value parts. Maps are functions, so given a map $M, the entry for a key $K can be obtained as the result of the function call $M($K).
Expanded QNames can be written in the notation "uri":local, allowing XPath expressions to be written that do not depend on an externally-supplied namespace context.

A number of new functions are available, including head, tail, map, filter, map-pairs, pi, sin, cos, tan, asin, acos, atan, sqrt, format-integer, and others. For details see .