Re: How to check a Float for NaN

[anon@anon.org (anon)]

Reference Microsoft and 

"isnan.asm" from 

http://www.visionlab.uncc.edu/websvn/filedetails.php?repname=toolchain&path=%2Fvendor%2Fvdsplibs%2Fcurrent%2Flibdsp%2Fisnan.asm&rev=1693&sc=1

The only mistake is that T > 16#7F000000# because I forgot to adjust 
for the the sign bit because NaN can have a valid sign set.

This work because in Intel the NaN is set by forcing bits 30-24 to 1 aka 
16#7F000000# 

The 
  T : Long_Long_Integer := Long_Long_Integer ( N ) ;
moves the bit-value of N a 48-bit float to a Long_Long_Integer (T)
without conversion. 



In <b42cb056-f923-45d9-9e01-d46d8376c41b@t12g2000prg.googlegroups.com>, Jerry <lanceboyle@qwest.net> writes:
>On May 9, 12:49=A0pm, a...@anon.org (anon) wrote:
>> =A0 --
>> =A0 -- Nan is define to be greater than value of hex 16#FF000000#
>> =A0 --
>>
>> =A0 function isNan ( N : Float ) return Boolean is
>>
>> =A0 =A0 =A0T : Long_Long_Integer :=3D Long_Long_Integer ( N ) ;
>>
>> =A0 =A0 begin
>> =A0 =A0 =A0 if T > 16#FF000000# then
>> =A0 =A0 =A0 =A0 return True ;
>> =A0 =A0 =A0 else
>> =A0 =A0 =A0 =A0 return False ;
>> =A0 =A0 =A0 end if ;
>> =A0 =A0 end ;
>>
>> In <3132e38d-18bb-4890-9cec-31056ac6e...@x19g2000prg.googlegroups.com>, Je=
>rry <lancebo...@qwest.net> writes:
>>
>> >How would one check a Float or Long_Float if it has value NaN? The
>> >only ways that I can come up with are to import a C function (isnan, I
>> >think) or to write Long_Float'image(Some_Float) to a string and
>> >examine the first three characters to see if they are "NaN" (and that
>> >seems to be a GNAT implementation choice so might not be portable,
>> >which is OK for my use).
>>
>> >Jerry
>
>No offense to anon, but does this work? Does anyone know of a
>reference for this definition of a NaN?
>
>Also, wondering how one might detect an Inf.
>
>It seems that there is enough information in this thread to begin
>writing a little package to deal with some of these things.
>
>Thanks for all the great tips, BTW.
>
>Jerry