add function to get multiple keys from maps and arrays

[line-o]

There is a need to get a sequence of properties from a map and indexes from an array.

TODO: There might be an obvious and simpler solution to this problem

xquery version "3.1";

declare function local:map-get-sequence ($map as map(*), $keys as xs:anyAtomicType* ) as item()* {
    for-each($keys, map:get($map, ?))
};

map { 1:2, 3:4, 5:6 } => local:map-get-sequence((1, 4, 5))
(: returns  (2, 6) :)

xquery version "3.1";
declare function local:array-get-sequence ($array as array(*), $indexes as xs:integer* ) as item()* {
    for-each($indexes, array:get($array, ?))
};

[2, 4, 6] => local:array-get-sequence((1, 3))
(: returns  (2, 6) :)

[line-o]

This does work as well:

[1,"s","s","s",5,"s","s"]
=> (function ($a, $s) { $a?($s) })((1,5))

[line-o]

It works for all function types (array and map)

map {1: "s", "s": "s", 5:"s", "a":()}
=> (function ($array-or-map as item(), $fields as xs:anyAtomicType*) { $array-or-map?($fields) })((1, "a"))