feat: implement std.avg (#1087)

* Add std.avg in standard library

Author: deepgoel17

doc/_stdlib_gen/stdlib-content.jsonnet

@@ -1394,6 +1394,16 @@ local html = import 'html.libsonnet';
             |||,
           ]),
         },
+        {
+          name: 'avg',
+          params: ['arr'],
+          availableSince: '0.20.0',
+          description: html.paragraphs([
+            |||
+              Return average of all element in <code>arr</code>.
+            |||,
+          ]),
+        },
         {
           name: 'remove',
           params: ['arr', 'elem'],

stdlib/std.jsonnet

@@ -1709,6 +1709,12 @@ limitations under the License.
 
   sum(arr):: std.foldl(function(a, b) a + b, arr, 0),
 
+  avg(arr)::
+    if std.length(arr) == 0 then
+      error 'Cannot calculate average of an empty array.'
+    else
+      std.sum(arr)/std.length(arr),
+
   minArray(arr, keyF=id, onEmpty=error 'Expected at least one element in array. Got none')::
     if std.length(arr) == 0 then
       onEmpty

test_suite/stdlib.jsonnet

@@ -1549,6 +1549,10 @@ std.assertEqual(std.all([]), true) &&
 
 std.assertEqual(std.sum([1, 2, 3]), 6) &&
 
+std.assertEqual(std.avg([1, 2, 3]), 2) &&
+std.assertEqual(std.avg([0, 0, 0]), 0) &&
+std.assertEqual(std.avg([1, 1, 2.5]), 1.5) &&
+
 std.assertEqual(std.minArray([1, 2, 3]), 1) &&
 std.assertEqual(std.minArray(['1', '2', '3']), '1') &&