Written Tutorial

Problem

You have a sequence and want to know whether each item in that sequence is also in another sequence.

Solution

Applies to MarkLogic versions 7+

declare function local:seq-contains($s1 as item()*, $s2 as item()*)
{
  every $s in $s1 satisfies $s = $s2
};

local:seq-contains((1, 2), (1, 2, 3, 4)) => true
local:seq-contains((2, 1), (1, 2, 3, 4)) => true (order does not matter)
local:seq-contains(('a', 'b', 'z'), ('a', 'b', 'c', 'd')) => false

Discussion

The line of code within the local:seq-contains function is a Quantified Expression. This will work with scalar values as well as with nodes, making it a flexible way of determining membership.