[task-416]

lib/plankton/plankton.d.ts

@@ -882,6 +882,9 @@ declare namespace lib_plankton.call {
     /**
      */
     export function sleep(seconds: float): Promise<void>;
+    /**
+     */
+    export function null_prop<type_value_from, type_value_to>(value_from: (null | type_value_from), function_: ((value: type_value_from) => type_value_to)): (null | type_value_to);
     export {};
 }
 declare namespace lib_plankton.file {

lib/plankton/plankton.js

@@ -2043,6 +2043,16 @@ var lib_plankton;
             }));
         }
         call.sleep = sleep;
+        /**
+         */
+        function null_prop(value_from, function_) {
+            return ((value_from === null)
+                ?
+                    null
+                :
+                    function_(value_from));
+        }
+        call.null_prop = null_prop;
     })(call = lib_plankton.call || (lib_plankton.call = {}));
 })(lib_plankton || (lib_plankton = {}));
 /*
@@ -3792,10 +3802,10 @@ var lib_plankton;
             options = Object.assign({
                 "compare_value": instance_compare
             }, options);
-            if (is_empty(list)) {
+            /*if (is_empty<type_element>(list)) {
                 throw (new Error("the max-arg of an empty list is not defined"));
             }
-            else {
+            else */ {
                 return (list
                     .reduce(function (result, element, index) {
                     var value = target_function(element);