update operator articles

Author: mumian

articles/azure-resource-manager/bicep/operators-access.md

@@ -3,7 +3,7 @@ title: Bicep accessor operators
 description: Describes Bicep resource access operator and property access operator.
 ms.topic: reference
 ms.custom: devx-track-bicep
-ms.date: 02/12/2025
+ms.date: 05/20/2025
 ---
 
 # Bicep accessor operators
@@ -13,6 +13,7 @@ The accessor operators are used to access child resources, properties on objects
 | Operator | Name |
 | ---- | ---- |
 | `[]` | [Index accessor](#index-accessor) |
+| `[^index]` | [Reverse index accessor](#reverse-index-accessor) |
 | `.`  | [Function accessor](#function-accessor) |
 | `::` | [Nested resource accessor](#nested-resource-accessor) |
 | `.`  | [Property accessor](#property-accessor) |
@@ -68,6 +69,52 @@ Output from the example:
 | ---- | ---- | ---- |
 | accessorResult | string | 'Development' |
 
+## Reverse index accessor
+
+Beginning with [Bicep CLI version 0.34.x](https://github.com/Azure/bicep/releases/tag/v0.34.1), the reverse index accessor operator (`^`) allows you to retrieve an element from an array or a character from a string by counting from the end. This one-based index means `^1` returns the last item, `^2` the second-to-last, and so on. The index must be a positive integer greater than zero and can be specified as a literal or an expression that evaluates to an integer.
+
+```bicep
+array[^index]
+string[^index]
+```
+
+### Remarks
+
+- The reverse index operator provides a convenient way to access elements or characters from the end of a sequence without calculating its length.
+- The index must be at least 1. Using `^0` results in a compilation error.
+- If the index exceeds the length of the array or string, a compilation error occurs for static indices, or a runtime error occurs for dynamic indices.
+- For constant arrays or strings, the operator is evaluated at compile time. For dynamic inputs, such as [parameters](./parameters.md), evaluation occurs at deployment time.
+
+### Example
+
+```bicep
+var items = [
+  'apple'
+  'banana'
+  'orange'
+  'grape'
+]
+
+output secondToLast string = items[^2]
+```
+
+Output from the example:
+
+| Name | Type | Value |
+| ---- | ---- | ---- |
+| secondToLast | string | 'orange' |
+
+```bicep
+var text = 'bicep'
+output secondToLastChar string = text[^2]
+```
+
+Output from the example:
+
+| Name | Type | Value |
+| ---- | ---- | ---- |
+| secondToLastChar | string | 'p' |
+
 ## Function accessor
 
 `resourceName.functionName()`

articles/azure-resource-manager/bicep/operators.md

@@ -3,7 +3,7 @@ title: Bicep operators
 description: Describes the Bicep operators available for Azure Resource Manager deployments.
 ms.topic: reference
 ms.custom: devx-track-bicep, devx-track-arm-template
-ms.date: 02/12/2025
+ms.date: 05/20/2025
 ---
 
 # Bicep operators
@@ -46,6 +46,7 @@ The accessor operators are used to access nested resources and properties on obj
 | Operator | Name | Description |
 | ---- | ---- | ---- |
 | `[]` | [Index accessor](./operators-access.md#index-accessor) | Access an element of an array or property on an object. |
+| `[^index]` | [Reverse index accessor](./operators-access.md#reverse-index-accessor) | Accesses an array element by index, counting from the end of the array (1-based from the end). |
 | `.` | [Function accessor](./operators-access.md#function-accessor) | Call a function on a resource. |
 | `::` | [Nested resource accessor](./operators-access.md#nested-resource-accessor) | Access a nested resource from outside of the parent resource. |
 | `.` | [Property accessor](./operators-access.md#property-accessor) | Access properties of an object. |