# dlaisnan.f - Man Page

## Synopsis

### Functions/Subroutines

logical function **dlaisnan** (DIN1, DIN2)**DLAISNAN** tests input for NaN by comparing two arguments for inequality.

## Function/Subroutine Documentation

### logical function dlaisnan (double precision, intent(in) DIN1, double precision, intent(in) DIN2)

**DLAISNAN** tests input for NaN by comparing two arguments for inequality.

**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.

**Parameters:***DIN1*DIN1 is DOUBLE PRECISION

*DIN2*DIN2 is DOUBLE PRECISION Two numbers to compare for inequality.

**Author:**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**June 2017

Definition at line 76 of file dlaisnan.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dlaisnan(3) is an alias of dlaisnan.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK