XQuery3.0: Mimicking a FLWOR expression with higher-order functions

gistfile1.xquery

xquery version "3.0";

declare function local:flwor(
  $ctxt as item(), 
  $find as function(item()) as item()*, 
  $predicate as function(item()) as xs:boolean,
  $orderBy as function(item()) as item()) as item()* {
    
  for $result in $find($ctxt)
  where $predicate($result)
  order by $orderBy($result)
  return $result
};  

declare function local:isMale($person as element(person)) as xs:boolean {
  $person/@gender = 'male'
}; 

declare function local:getPersons($persons as element(persons)) as element(person)* {  
  $persons/person
};  
 
 
let $persons :=
<persons>
  <person gender="male">
    <country>Belgium</country>
    <name>John</name>
    <age>10</age>
  </person>
  <person gender="male">
    <country>Netherlands</country>
    <name>Robby</name>
    <age>20</age>
  </person>
  <person gender="female">
    <country>Belgium</country>
    <name>Linda</name>
    <age>80</age>
  </person>
  <person gender="male">
    <country>Belgium</country>
    <name>Davy</name>
    <age>40</age>
  </person>
  <person gender="female">
    <country>Netherlands</country>
    <name>Alice</name>
    <age>30</age>
  </person>
  <person gender="male">
    <country>Netherlands</country>
    <name>Albert</name>
    <age>36</age>
  </person> 
</persons>
 
let $getPersons := local:getPersons#1
let $isMale := local:isMale#1

return local:flwor(
  $persons, 
  $getPersons, 
  $isMale,
  function($person as element(person)) as item() { $person/name}   
)

(:
****************************************************************
XQuery output: We expect a sequence of all males ordered by name
****************************************************************
<person gender="male">
  <country>Netherlands</country>
  <name>Albert</name>
  <age>36</age>
</person>
<person gender="male">
  <country>Belgium</country>
  <name>Davy</name>
  <age>40</age>
</person>
<person gender="male">
  <country>Belgium</country>
  <name>John</name>
  <age>10</age>
</person>
<person gender="male">
  <country>Netherlands</country>
  <name>Robby</name>
  <age>20</age>
</person>
:)