Add examples of recursive methods

qt4cg · Dec 22, 2023 · ee2bccc · ee2bccc
1 parent 2856af5
commit ee2bccc
Showing 1 changed file with 25 additions and 1 deletion.
diff --git a/specifications/xquery-40/src/expressions.xml b/specifications/xquery-40/src/expressions.xml
@@ -9712,7 +9712,7 @@ return $incrementors[2](4)]]></eg>
 
             <example id="id-example-method-updating">
                <head>Example of an updating method</head>
-               <p>The following examble demonstrates how a method might be used to increase
+               <p>The following example demonstrates how a method might be used to increase
                the size of a rectangle by a given factor.</p>
 
                <eg><![CDATA[declare item type geo:rect as record(
@@ -9735,7 +9735,31 @@ declare function geo:rectangle(
                <ednote><edtext>Depends on resolution of issue 296 (recursive record types)</edtext></ednote>
 
             </example>
+
+            <p>Methods can be used to deliver recursive inline functions, as shown in the example below.</p>
 
+            <example id="id-example-method-recursve">
+               <head>Example of recursive method</head>
+               <p>The following example implements an anonymous function that computes
+                  the product of sequence of numbers:</p>
+
+               <eg><![CDATA[let $product := 
+    map{"_product": %method fn($in) {
+       if (empty($in))
+       then 1
+       else head($in) * $self?_product(tail($in))}
+    }?_product
+return $product((1.05, 1.04, 1.03))]]></eg>
+
+               <p>The next example illustrates a library of functions that are mutually
+               recursive:</p>
+
+               <eg><![CDATA[let $lib := 
+    map{"even": %method fn($val) {$val = 0 or $self?odd(abs($val)-1)},
+        "odd":  %method fn($val) {not($self?even($val))}
+       }
+return $lib?odd(23)]]></eg>
+            </example>
 
          </div3>