September 2017 Update

Task/Symmetric-difference/Jq/symmetric-difference-1.jq

@@ -0,0 +1,10 @@
+# The following implementation of intersection (but not symmetric_difference) assumes that the
+# elements of a (and of b) are unique and do not include null:
+def intersection(a; b):
+  reduce ((a + b) | sort)[] as $i
+    ([null, []]; if .[0] == $i then [null, .[1] + [$i]] else [$i, .[1]] end)
+  | .[1] ;
+
+def symmetric_difference(a;b):
+  (a|unique) as $a | (b|unique) as $b
+  | (($a + $b) | unique) - (intersection($a;$b));

Task/Symmetric-difference/Jq/symmetric-difference-2.jq

@@ -0,0 +1,2 @@
+symmetric_difference( [1,2,1,2]; [2,3] )
+[1,3]