isinf

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.

Usage

Syntax

isinf(x)

Parameters

Returns

true if x is positive or negative infinity. false for finite values and NaN.

List of related functions

• 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 aren't a concern.
• log: Returns the natural logarithm. Compute log on potentially zero or negative values and use isinf to detect the resulting -inf.

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