Add fn:partition, and change a couple of examples

specifications/xpath-functions-40/src/function-catalog.xml

@@ -19579,7 +19579,7 @@ chain((1, 2, 3, 4), $product3)
          <eg><![CDATA[
 declare %private function while-do-helper(
   $input     as item()*,
-  $predicate as function(item()*, xs:integer) as xs:boolean,
+  $predicate as function(item()*, xs:integer) as xs:boolean?,
   $action    as function(item()*, xs:integer) as item()*,
   $pos       as xs:integer
 ) as item()* {
@@ -19590,7 +19590,7 @@ declare %private function while-do-helper(
 
 declare function while-do(
   $input     as item()*,
-  $predicate as function(item()*, xs:integer) as xs:boolean,
+  $predicate as function(item()*, xs:integer) as xs:boolean?,
   $action    as function(item()*, xs:integer) as item()*
 ) as item()* {
   while-do-helper($input, $predicate, $action, 1)
@@ -19729,7 +19729,7 @@ return $result?numbers
 declare %private function do-until-helper(
   $input     as item()*,
   $action    as function(item()*, xs:integer) as item()*,
-  $predicate as function(item()*, xs:integer) as xs:boolean,
+  $predicate as function(item()*, xs:integer) as xs:boolean?,
   $pos       as xs:integer
 ) as item()* {
   let $result := $action($input, $pos)
@@ -19743,7 +19743,7 @@ declare %private function do-until-helper(
 declare function do-until(
   $input     as item()*,
   $action    as function(item()*, xs:integer) as item()*,
-  $predicate as function(item()*, xs:integer) as xs:boolean
+  $predicate as function(item()*, xs:integer) as xs:boolean?
 ) as item()* {
   do-until-helper($input, $action, $predicate, 1)
 };]]></eg>
@@ -30646,7 +30646,7 @@ path with an explicit <code>file:</code> scheme.</p>
       <fos:signatures>
          <fos:proto name="partition" return-type="array(item())*">
             <fos:arg name="input" type="item()*"/>
-            <fos:arg name="split-when" type="function(item()*, item(), xs:integer) as xs:boolean"/>
+            <fos:arg name="split-when" type="function(item()*, item(), xs:integer) as xs:boolean?"/>
          </fos:proto>
       </fos:signatures>
       <fos:properties>
@@ -30668,7 +30668,7 @@ path with an explicit <code>file:</code> scheme.</p>
             the sequence of arrays.</p>
          <p>If the <code>$split-when</code> function returns <code>true</code>, the current partition is wrapped as an array and added to the result,
             and a new current partition is created, initially containing the item <var>J</var> only. If the <code>$split-when</code> 
-            function returns <code>false</code>, the item <var>J</var> is added to the current partition.</p>
+            function returns <code>false</code> or <code>()</code>, the item <var>J</var> is added to the current partition.</p>
          <p>More formally, the function returns the result of the expression:</p>
          <eg>fold-left($input, (), fn($partitions, $next, $pos) {
   if (empty($partitions) or $split-when(foot($partitions)?*, $next, $pos))