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<h1>New features in XPath 3.0</h1>
<div class="boxed"
style="border: solid thin; background-color: #B1CCC7; padding: 2px">These features are available in Saxon only if explicitly enabled, either directly, or by requesting
support for XSLT 3.0 or XQuery 3.0. In both cases, this requires Saxon-PE or above.</div>
<p>Some of the new features in XPath 3.0 are as follows. For full details, see the W3C specifications.</p>
<ol>
<li>
<p>The concatenation operator <code>||</code> is available (as in SQL). For example,
<code>('$' || 12.5)</code> returns the string '$12.5'.</p>
</li>
<li>
<p>A new simple mapping operator is available, <code>!</code>. This works rather like <code>/</code>,
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, <code>(1 to 7)!(.*.)</code> returns the sequence
<code>(1, 4, 9, 16, 25, 36, 49)</code>.</p>
</li>
<li>
<p>Local variables can be declared in a <code>let</code> expression, for example
<code>let $x := /*/@version return //e[@version = $x]</code></p>
</li>
<li>
<p>Inline function items can be declared, and used as arguments to higher-order
functions. For example <code>map(//employee, function($e){$e/salary + $e/bonus})</code>.
A <i>function item</i> is a third kind of item, alongside nodes and atomic values.
The function represented by a function item <code>$f</code> can be invoked using a dynamic
function call <code>$f(args)</code>.</p>
</li>
<li>
<p>Maps are available (for more details see <a class="bodylink" href="../expressions/xpath30maps.xml">Maps</a>.
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
<a class="bodylink" href="../functions/intro.xml">XSLT 2.0 and XPath 2.0 Functions</a>), and in addition there is new syntax for a map constructor
(of the form <code>map{ key := value, key := value }</code> where both the keys and values
are arbitrary expressions. There is a sequenceType for maps: <code>map(K, V)</code>
defining the types of the key and value parts. Maps are functions, so given a map $M,
the entry for a key $K can be obtained as the result of the function call <code>$M($K)</code>.</p>
</li>
<li>
<p>Expanded QNames can be written in the notation <code>"uri":local</code>, allowing
XPath expressions to be written that do not depend on an externally-supplied namespace context.</p>
</li>
</ol>
<p>A number of new functions are available, including <code>head</code>, <code>tail</code>, <code>map</code>,
<code>filter</code>, <code>map-pairs</code>, <code>pi</code>, <code>sin</code>, <code>cos</code>, <code>tan</code>,
<code>asin</code>, <code>acos</code>, <code>atan</code>, <code>sqrt</code>, <code>format-integer</code>, and others.
For details see <a class="bodylink" href="../functions/intro.xml">XSLT 2.0 and XPath 2.0 Functions</a>.</p>
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