todouble, toreal

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

Use the todouble function (or its synonym toreal) to convert various data types to a real (floating-point) number. This is helpful when you need to normalize numeric values from different sources into decimal format for mathematical operations, comparisons, or aggregations.

You typically use todouble when working with numeric strings, integers, or other types that need to be converted to floating-point numbers for precise calculations or when decimal precision is required.

Usage

Syntax

APL

todouble(value)
toreal(value)

Parameters

Name	Type	Description
value	dynamic	The value to convert to real.

Returns

If conversion is successful, the result is a value of type real. If conversion isn't successful, the result is null.

Conversion behavior

The todouble function converts values based on their type:

Integer: Converted to float. For example, 1 becomes 1.0, -1 becomes -1.0.
String: Parsed as a 64-bit float using Go floating-point literal syntax, which supports scientific notation. For example, "1e3" becomes 1000.0.
Boolean: true becomes 1.0, false becomes 0.0
Datetime: Converted to nanoseconds since epoch as a float
Duration: Converted to float nanoseconds

Use case examples

Convert string representations of numeric values to real numbers for mathematical calculations and aggregations.

Query

APLRun in Playground

['sample-http-logs']
| extend duration_seconds = todouble(['req_duration_ms']) / 1000.0
| extend is_slow = duration_seconds > 0.001
| where is_slow == true
| project _time, ['uri'], ['req_duration_ms'], duration_seconds, is_slow

Output

_time	uri	req_duration_ms	duration_seconds	is_slow
Jun 24, 09:28:10	/api/users	1500	1.5	true

This example converts milliseconds to seconds using todouble to ensure decimal precision in the calculation, enabling accurate time-based analysis.

Convert trace duration values to real numbers for precise duration calculations and percentile analysis.

Query

APLRun in Playground

['otel-demo-traces']
| extend duration_ms = todouble(['duration']) / 1000000.0
| extend is_slow_span = duration_ms > 100.0
| where is_slow_span == true
| project _time, ['trace_id'], ['service.name'], ['duration'], duration_ms, is_slow_span

Output

_time	trace_id	service.name	duration	duration_ms	is_slow_span
Jun 24, 09:28:10	abc123	frontend	150000000	150.0	true

This example converts nanosecond durations to milliseconds using todouble to maintain decimal precision, enabling accurate performance analysis of trace spans.

Convert numeric security metrics to real numbers for threshold-based security analysis and alerting.

Query

APLRun in Playground

['sample-http-logs']
| extend risk_score = todouble(['req_duration_ms']) / 100.0
| extend is_high_risk = risk_score > 0.01
| where is_high_risk == true
| project _time, ['uri'], ['status'], ['req_duration_ms'], risk_score, is_high_risk

Output

_time	uri	status	req_duration_ms	risk_score	is_high_risk
Jun 24, 09:28:10	/admin	403	5500	55.0	true

This example converts request duration to a risk score using todouble to enable precise threshold-based security analysis with decimal precision.

toreal: Synonym for todouble. Both functions convert values to real numbers.
toint: Converts input to integer. Use toint when you need whole numbers, and todouble when you need decimal precision.