Switch in rank expressions documentation

en/ranking/ranking-expressions-features.html

@@ -233,7 +233,16 @@ <h3 id="accessing-feature-function-values-in-results">Accessing feature/function
 
 
 
-<h2 id="the-if-function-and-string-equality-tests">The "if" function and string equality tests</h2>
+<h2 id="conditional-expressions">Conditional expressions</h2>
+
+<p>
+Ranking expressions support conditional logic to choose between different sub-expressions based on document attributes, query parameters, or other features.
+This enables ranking to adapt to different document types, user segments, or business rules within a single rank profile.
+</p>
+
+
+<h3 id="the-if-function">The if function</h3>
+<span id="the-if-function-and-string-equality-tests"></span>
 
 <p>
 <code>if</code> can be used for other purposes than encoding MLR trained decision trees.
@@ -268,6 +277,27 @@ <h2 id="the-if-function-and-string-equality-tests">The "if" function and string
 </p>
 
 
+<h3 id="the-switch-function">The switch function</h3>
+<p>
+When comparing many values against the same discriminant value,
+the <code>switch</code> function provides a more readable alternative to deeply nested <code>if</code> statements.
+For example, the nested if expression above can be written more clearly as:
+</p>
+<pre>
+switch (attribute(category)) {
+    case "restaurant": <em>&hellip;restaurant function</em>,
+    case "hotel": <em>&hellip;hotel function</em>,
+    default: <em>&hellip;default function</em>
+}
+</pre>
+<p>
+Use <code>switch</code> when testing a single expression for equality against multiple values.
+Continue using <code>if</code> for different comparison operators or when each condition tests different expressions,
+such as in the tiering example above.
+See the <a href="../reference/ranking/ranking-expressions.html#the-switch-function">switch function reference</a> for details.
+</p>
+
+
 <h2 id="using-constants">Using constants</h2>
 
 <p>

en/reference/ranking/ranking-expressions.html

@@ -172,6 +172,31 @@ <h2 id="the-if-function">The if function</h2>
 
 
 
+<h2 id="the-switch-function">The switch function</h2>
+{% include note.html content='Available from Vespa 8.626.55' %}
+<p>
+The <code>switch</code> function chooses between multiple sub-expressions based on matching a value.
+It provides a more readable alternative to chained <code>if</code> statements when selecting from several options.
+</p>
+<pre>
+switch (discriminant) {
+    case value1: result1,
+    case value2: result2,
+    ...
+    default: defaultResult
+}
+</pre>
+<p>
+The <code>discriminant</code> expression is compared for equality against each <code>case</code> value expression in order.
+When a match is found, the corresponding result expression is evaluated and returned.
+If no case matches, the <code>default</code> result is returned.
+All expressions may be any ranking expression.
+At least one <code>case</code> must be specified.
+The <code>default</code> must be specified.
+</p>
+
+
+
 <h2 id="the-foreach-function">The foreach function</h2>
 <p>
 The foreach function is not really part of the expression language but implemented as a