September 2017 Update

Task/Remove-duplicate-elements/Jq/remove-duplicate-elements-1.jq

@@ -0,0 +1 @@
+[4,3,2,1,1,2,3,4] | unique

Task/Remove-duplicate-elements/Jq/remove-duplicate-elements-2.jq

@@ -0,0 +1,24 @@
+def removeAllButFirst:
+
+  # The hash table functions all expect the hash table to be the input.
+
+  # Is x in the hash table?
+  def hashed(x):
+    (x|tostring) as $value
+    | .[$value] as $bucket
+    | $bucket and (.[$value] | index([x]));
+
+  # Add x to the hash table:
+  def add_hash(x):
+    (x|tostring) as $value
+    | .[$value] as $bucket
+    | if $bucket and ($bucket | index([x])) then .
+      else .[$value] += [x]
+      end;
+
+  reduce .[] as $item
+    ( [[], {}]; # [array, hash]
+      if .[1] | hashed($item) then .
+      else [ (.[0] + [$item]), (.[1] | add_hash($item)) ]
+      end)
+  | .[0];