isreal

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

Use the isreal function to determine whether a value is a real number. This function is helpful when you need to validate data before performing numeric operations. For example, you can use isreal to filter out invalid values which could otherwise disrupt aggregations or calculations.

You often use isreal in data cleaning pipelines, conditional logic, and when inspecting metrics like durations, latencies, or numeric identifiers. It’s especially useful when working with telemetry or log data that includes optional or incomplete numeric fields.

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

Splunk uses the isnum function to check whether a string represents a numeric value.

Splunk example

... | eval is_valid = if(isnum(duration), "yes", "no")

ANSI SQL users

ANSI SQL does not have a direct equivalent to isreal. You typically check for numeric values using IS NOT NULL and avoid known invalid markers manually. APL’s isreal abstracts this by directly checking if a value is a real number.

SQL example

SELECT *, 
       CASE WHEN duration IS NOT NULL THEN 'yes' ELSE 'no' END AS is_valid
FROM traces

Usage

Syntax

isreal(value)

Parameters

Name	Type	Description
value	any	The input value to evaluate.

Returns

Returns true if the input is a valid real number. Returns false for strings, nulls, or non-numeric types.

Example

Use isreal to identify real number values.

Query

['sample-http-logs'] 
| extend is_real = isreal(123.11)

Run in Playground

Output

_time	is_real
2025-06-05T12:01:00Z	true

List of related functions

• ismap: Checks whether a value is of the dynamic type and represents a mapping.
• isstring: Checks whether a value is a string. Use this for scalar string validation.