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Use the isinf function in APL to check whether a numeric value is positive or negative infinity. The function returns true only when the value is ±∞ and false for all finite values and NaN. isinf is useful for detecting overflow conditions or division-by-zero results in computed columns. Unlike isfinite, which also catches NaN values, isinf specifically targets infinite results, allowing you to distinguish overflow from undefined computations.

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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 doesn’t have a direct isinf() function. You typically check whether a value equals a specific infinity representation, which isn’t directly available in most SPL expressions.
| eval is_inf = if(value = 'Infinity' OR value = '-Infinity', 1, 0)
Standard SQL does not define an ISINF() function. Most SQL databases raise an error on division by zero rather than producing infinity, so there is no direct equivalent.
-- Division by zero raises an error in most SQL dialects; no direct ISINF() equivalent
SELECT CASE WHEN value > 1e308 OR value < -1e308 THEN 1 ELSE 0 END AS is_inf FROM logs

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Usage

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Syntax

isinf(x)

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Parameters

NameTypeRequiredDescription
xrealYesThe numeric value to check.

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Returns

true if x is positive or negative infinity. false for finite values and NaN.
  • isfinite: Returns true for values that are neither infinite nor NaN. Use it for a broader check covering all invalid float states.
  • isnan: Returns true only for NaN values. Use it alongside isinf to detect the other class of invalid float.
  • isint: Returns true for integer values. Use it when you need to validate that a value is a whole number.
  • not: Reverses a boolean value. Use not(isinf(x)) as a shorthand for isfinite(x) when NaN values are not a concern.
  • log: Returns the natural logarithm. Compute log on potentially zero or negative values and use isinf to detect the resulting -inf.