Add get field value from record with default

* Format getor function and add example
* Add get_or function for records
* Add at_or returing n-th value or default

core/stdlib/std.ncl

@@ -172,6 +172,25 @@
         "%
       = fun n l => %elem_at% l n,
 
+    at_or
+      : forall a. Number -> a -> Array a -> a
+      | doc m%"
+          Retrieves the n-th element from an array, with indices starting at 0
+          or provided value in case index is out of bounds.
+
+          # Examples
+
+          ```nickel
+          std.array.at 3 "default" [ "zero", "one" ] =>
+            "default"
+          ```
+        "%
+      = fun n default_value array =>
+        if n < %length% array then
+          %elem_at% array n
+        else
+          default_value,
+
     concat
       : forall a. Array a -> Array a -> Array a
       | doc m%"
@@ -2148,6 +2167,28 @@
       "%%
       = fun field r => r."%{field}",
 
+    get_or
+      : forall a. String -> a -> { _ : a } -> a
+      | doc m%%"
+        Returns the field of a record with given name or default value,
+        if there is no such field.
+
+        # Examples
+
+        ```nickel
+        std.record.get_or "tree" 3 { one = 1, two = 2 } =>
+          3
+
+        std.record.get_or "one" 11 { one = 1, two = 2 } =>
+          1
+        ```
+      "%%
+      = fun field default_value record =>
+        if %has_field% field record then
+          record."%{field}"
+        else
+          default_value,
+
     insert
       : forall a. String -> a -> { _ : a } -> { _ : a }
       | doc m%%"