---
name: "dlaisnan"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/dlaisnan/3lapack"
---

# dlaisnan(3lapack)

routine i not for general use

## NAME

DLAISNAN - routine i not for general use

## SYNOPSIS

- LOGICAL FUNCTION

  DLAISNAN(DIN1,DIN2)

- DOUBLE

  PRECISION DIN1,DIN2

## PURPOSE

This routine is not for general use.  It exists solely to avoid over-optimization in DISNAN.\
 DLAISNAN checks for NaNs 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.\
 A compiler must assume that the two arguments are\
 not the same variable, and the test will not be optimized away. Interprocedural or whole-program optimization may delete this test.  The ISNAN functions will be replaced by the correct Fortran 03 intrinsic once the intrinsic is widely available.

## ARGUMENTS

- DIN1 (input) DOUBLE PRECISION

  DIN2     (input) DOUBLE PRECISION Two numbers to compare for inequality.