Add std.maxArray in standard library (#1081)

Co-authored-by: Dave Cunningham <sparkprime@gmail.com>

Author: deepgoel17

doc/_stdlib_gen/stdlib-content.jsonnet

@@ -1350,6 +1350,14 @@ local html = import 'html.libsonnet';
             |||
               Return the min of all element in <code>arr</code>.
         },
+        {
+          name: 'maxArray',
+          params: ['arr', 'keyF', 'onEmpty'],
+          availableSince: 'upcoming',
+          description: html.paragraphs([
+            |||
+              Return the max of all element in <code>arr</code>.
+        },
         {
           name: 'contains',
           params: ['arr', 'elem'],

stdlib/std.jsonnet

@@ -1715,6 +1715,18 @@ limitations under the License.
           a;
       std.foldl(minFn, arr, minVal),
 
+  maxArray(arr, keyF=id, onEmpty=error 'Expected at least one element in array. Got none')::
+    if std.length(arr) == 0 then
+      onEmpty
+    else
+      local maxVal = arr[0];
+      local maxFn(a, b) =
+        if std.__compare(keyF(a), keyF(b)) < 0 then
+          b
+        else
+          a;
+      std.foldl(maxFn, arr, maxVal),
+
   xor(x, y):: x != y,
 
   xnor(x, y):: x == y,

test_suite/stdlib.jsonnet

@@ -1547,6 +1547,11 @@ std.assertEqual(std.sum([1, 2, 3]), 6) &&
 std.assertEqual(std.minArray([1, 2, 3]), 1) &&
 std.assertEqual(std.minArray(['1', '2', '3']), '1') &&
 
+std.assertEqual(std.maxArray([1, 2, 3]), 3) &&
+std.assertEqual(std.maxArray(['1', '2', '3']), '3') &&
+std.assertEqual(std.maxArray(['a', 'x', 'z']), 'z') &&
+
+
 std.assertEqual(std.xor(true, false), true) &&
 std.assertEqual(std.xor(true, true), false) &&