Add a unique function.

builtin.c

@@ -295,6 +295,7 @@ static const char* jq_builtins[] = {
   "def select(f): if f then . else empty end;",
   "def sort_by(f): _sort_by_impl(map([f]));",
   "def group_by(f): _group_by_impl(map([f]));",
+  "def unique: group_by(.) | map(.[0]);",
 };
 
 

docs/content/3.manual/manual.yml

@@ -542,6 +542,18 @@ sections:
             input: '[{"foo":1, "bar":10}, {"foo":3, "bar":100}, {"foo":1, "bar":1}]'
             output: ['[[{"foo":1, "bar":10}, {"foo":1, "bar":1}], [{"foo":3, "bar":100}]]']
 
+      - title: `unique`
+        body: |
+          
+          The `unique` function takes as input an array and produces
+          an array of the same elements, in sorted order, with
+          duplicates removed.
+
+        examples:
+          - program: 'unique'
+            input: '[1,2,5,3,5,3,1,3]'
+            output: ['[1,2,3,5]']
+
       - title: `contains`
         body: |
 

testdata

@@ -448,3 +448,7 @@ sort
 [{"a": 4, "b": 1, "c": 3}, {"a": 0, "b": 2, "c": 43}, {"a": 1, "b": 4, "c": 3}, {"a": 1, "b": 4, "c": 14}]
 [[{"a": 4, "b": 1, "c": 3}], [{"a": 0, "b": 2, "c": 43}], [{"a": 1, "b": 4, "c": 14}, {"a": 1, "b": 4, "c": 3}]]
 [[{"a": 1, "b": 4, "c": 14}, {"a": 0, "b": 2, "c": 43}], [{"a": 4, "b": 1, "c": 3}, {"a": 1, "b": 4, "c": 3}]]
+
+unique
+[1,2,5,3,5,3,1,3]
+[1,2,3,5]