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C Library Functions  - is_nan (3)

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NAME

is_nan(3f) - [M_units] determine if integer is a Nan (Not a Number) value (LICENSE:PD)

CONTENTS

Synopsis
Description
Options
Example
Author
License

SYNOPSIS

elemental pure logical is_nan(value)

     integer(kind=real32|real64|real128|complex) :: value

DESCRIPTION

Determine if a real or complex value is a NaN (Not a Number) value

OPTIONS

value	The value to test

EXAMPLE

simple example

    program demo_is_nan
    use M_units, only : is_nan
    real :: x
    character(len=*),parameter   :: linei=’Infinity’
    character(len=*),parameter   :: line=’NaN’
    character(len=:),allocatable :: readable
    real,parameter :: arr(*)=[-100.0,100.0,huge(0.0)]
       readable=linei
       read(readable,*)x
       write(*,*)is_nan(x),x   ! note Infinity is not a Nan
       write(*,*)is_nan(-x),-x
       readable=line
       read(readable,*)x
       write(*,*)is_nan(x),x
       write(*,*)x==x,x  ! note Nan is never equal to another value
       write(*,*)is_nan(arr),arr
    end program demo_is_nan

Expected results

    F         Infinity
    F        -Infinity
    T              NaN
    F              NaN
    F F F  -100.000000       100.000000       3.40282347E+38

AUTHOR

John S. Urban

LICENSE

Public Domain

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Nemo Release 3.1

is_nan (3)

June 29, 2025

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