reverse

This page explains how to use the reverse function in APL.

The reverse function reverses the order of characters in a string. Use this function to analyze strings from right to left, detect palindromes, or transform data for specific pattern matching requirements.

For users of other query languages

If you come from other query languages, this section explains how to adjust your existing queries to achieve the same results in APL.

Splunk SPL users

In Splunk SPL, reversing strings typically requires custom functions or scripts. APL’s reverse provides this functionality natively.

Splunk example

| eval reversed=mvreverse(split(field, ""))| eval reversed=mvjoin(reversed, "")

ANSI SQL users

In ANSI SQL, string reversal varies by database with different functions. APL’s reverse provides standardized string reversal.

SQL example

SELECT REVERSE(field) AS reversed FROM logs;

Usage

Syntax

reverse(value)

Parameters

Name	Type	Required	Description
value	string	Yes	The input string to reverse.

Returns

Returns the input string with its characters in reverse order.

Use case examples

Log analysis

Detect palindromic patterns in URIs or identifiers for data validation.

Query

['sample-http-logs']
| extend reversed_uri = reverse(uri)
| extend is_palindrome = uri == reversed_uri
| summarize palindrome_count = countif(is_palindrome), total_count = count() by method
| extend palindrome_percentage = round(100.0 * palindrome_count / total_count, 2)
| sort by palindrome_count desc

Run in Playground

Output

method	palindrome_count	total_count	palindrome_percentage
GET	12	8765	0.14
POST	5	2341	0.21
PUT	2	987	0.20

This query detects palindromic URIs by comparing them with their reversed versions, which can help identify unusual or test data patterns.

List of related functions

• substring: Extracts parts of strings. Use this with reverse to extract from the end of strings.
• strlen: Returns string length. Use this with reverse for position calculations from the right.
• strcat: Concatenates strings. Use this to build strings with reversed components.
• split: Splits strings into arrays. Use this with reverse to process tokens in reverse order.