cover nullable type modifier

Author: mumian

articles/azure-resource-manager/bicep/data-types.md

@@ -2,7 +2,7 @@
 title: Data types in Bicep
 description: This article describes the data types that are available in Bicep.
 ms.topic: reference
-ms.date: 06/30/2025
+ms.date: 07/07/2025
 ms.custom: devx-track-bicep
 ---
 
@@ -437,6 +437,16 @@ The union type has some limitations:
 
 You can use the union type syntax in [user-defined data types](./user-defined-data-types.md).
 
+## Nullable Types
+
+You can make any primitive or complex type nullable by appending a `?` to the type name. This allows the parameter, variable, or output to accept null as a valid value. For example:
+
+```bicep
+param description string? = null
+param config object? = null
+output optionalValue int? = null
+```
+
 ## Secure strings and objects
 
 Secure strings use the same format as string, and secure objects use the same format as object. With Bicep, you add the `@secure()` [decorator](./parameters.md#use-decorators) to a string or object.

articles/azure-resource-manager/templates/template-functions-array.md

@@ -227,7 +227,7 @@ The output from the preceding example with the default values is:
 
 `indexFromEnd(sourceArray, reverseIndex)`
 
-Returns an element of the array by counting backwards from the end. This is useful when you want to reference elements starting from the end of a list, rather than the beginning. The [`tryIndexFromEnd()`](#tryindexfromend) function is a safe version of `indexFromEnd()`.
+Returns an element of the array by counting backwards from the end. This is useful when you want to reference elements starting from the end of a list, rather than the beginning. The [`tryIndexFromEnd`](#tryindexfromend) function is a safe version of `indexFromEnd`.
 
 In Bicep, use the [Reserved index accessor](../bicep/operators-access.md#reverse-index-accessor) operator.
 
@@ -244,7 +244,7 @@ A single element from an array, selected by counting backward from the end of th
 
 ### Example
 
-The following example shows how to use the first function with an array and string.
+The following example shows how to use the `indexFromEnd` function.
 
 ```json
 {
@@ -748,7 +748,7 @@ The output from the preceding example with the default values is:
 
 `tryndexFromEnd(sourceArray, reverseIndex)`
 
-The `tryIndexFromEnd()` function is a safe version of [`indexFromEnd()`](#indexFromEnd). It retrieves a value from an array by counting backward from the end without throwing an error if the index is out of range.
+The `tryIndexFromEnd` function is a safe version of [`indexFromEnd`](#indexfromend). It retrieves a value from an array by counting backward from the end without throwing an error if the index is out of range.
 
 In Bicep, use the [Reserved index accessor](../bicep/operators-access.md#reverse-index-accessor) operator and the [Safe dereference](../bicep/operator-safe-dereference.md#safe-dereference) operator.
 
@@ -815,7 +815,7 @@ The following example shows an out-of-bound scenario:
   },
   "resources": {},
   "outputs": {
-    "secondToLast": {
+    "outOfBound": {
       "type": "string",
       "nullable": true,
       "value": "[tryIndexFromEnd(parameters('items'), 5)]"
@@ -828,7 +828,7 @@ The output from the preceding example with the default values is:
 
 | Name | Type | Value |
 | ---- | ---- | ----- |
-| secondToLast | String | (null) |
+| outOfBound | String | (null) |
 
 ## union
 

articles/azure-resource-manager/templates/toc.yml

@@ -469,7 +469,7 @@ items:
     - name: All functions
       href: template-functions.md
     - name: Array functions
-      displayName: array,concat,contains,createArray,empty,first,indexOf,intersection,last,lastIndexOf,length,max,min,range,skip,take,union
+      displayName: array,concat,contains,createArray,empty,first,indexFromEnd,indexOf,intersection,last,lastIndexOf,length,max,min,range,skip,take,tryIndexFromEdn,union
       href: template-functions-array.md
     - name: CIDR functions
       displayName: parseCidr,cidrSubnet,cidrHost