[refactor] make use of HoFs in test:apply

Seems to be a tad faster even.

Author: line-o

exist-core/src/main/resources/org/exist/xquery/lib/xqsuite/xqsuite.xql

@@ -716,28 +716,17 @@ declare function test:apply($func as function(*), $meta as element(function), $a
 };
 
 (:~
- : Call the given function with parameters taken from $args.
+ : Call the given function with parameters taken from $args
+ : since the items in the $args sequence are itself functions
+ : apply them first.
+ : The maximum number of items in $args is set to seven.
  :)
-declare %private function test:apply($func as function(*), $args as item()*) {
-    switch (count($args))
-        case 0 return
-            $func()
-        case 1 return
-            $func($args[1]())
-        case 2 return
-            $func($args[1](), $args[2]())
-        case 3 return
-            $func($args[1](), $args[2](), $args[3]())
-        case 4 return
-            $func($args[1](), $args[2](), $args[3](), $args[4]())
-        case 5 return
-            $func($args[1](), $args[2](), $args[3](), $args[4](), $args[5]())
-        case 6 return
-            $func($args[1](), $args[2](), $args[3](), $args[4](), $args[5](), $args[6]())
-        case 7 return
-            $func($args[1](), $args[2](), $args[3](), $args[4](), $args[5](), $args[6](), $args[7]())
-        default return
-            error($test:WRONG_ARG_COUNT, "Function takes too many arguments")
+declare %private function test:apply($func as function(*), $args as function(*)*) {
+    if (count($args) gt 7)
+    then error($test:WRONG_ARG_COUNT, "Function takes too many arguments")
+    else apply($func,
+        array:for-each(array{ $args }, (: iterate over an array to supply the arguments to apply :)
+            apply(?, [])))       (: same as $args[$n]() :)
 };
 
 declare %private function test:get-test-name($meta as element(function)) as xs:string {
@@ -752,8 +741,11 @@ declare %private function test:get-test-name($meta as element(function)) as xs:s
 (:~
  : Print out evaluation results for a given test.
  :)
-declare %private function test:print-result($meta as element(function), $result as item()*,
-        $assertResult as element(report)*) {
+declare %private function test:print-result(
+        $meta as element(function),
+        $result as item()*,
+        $assertResult as element(report)*
+) {
     <testcase name="{test:get-test-name($meta)}" class="{$meta/@name}">
     {
         if (exists($assertResult)) then