# ?laisnan

Tests input for `NaN`.

## Syntax

val = slaisnan( sin1, sin2 )

val = dlaisnan( din1, din2 )

## Description

This logical routine checks for NaNs (NaN stands for 'Not A Number') by comparing its two arguments for inequality. NaN is the only floating-point value where `NaN ≠ NaN` returns .TRUE. To check for NaNs, pass the same variable as both arguments.

This routine is not for general use. It exists solely to avoid over-optimization in ?isnan.

## Input Parameters

sin1, sin2

  REAL for sisnan

  Two numbers to compare for inequality.

din2, din2

  DOUBLE PRECISION for disnan

  Two numbers to compare for inequality.

## Output Parameters

val

  Logical. Result of the comparison.

Parent topic: Auxiliary Routines