Beefy Boxes and Bandwidth Generously Provided by pair Networks
We don't bite newbies here... much
 
PerlMonks  

Re: Extracting IEEE 754 floating point numbers

by physgreg (Scribe)
on Oct 29, 2002 at 09:32 UTC ( #208692=note: print w/replies, xml ) Need Help??


in reply to Extracting IEEE 754 floating point numbers

Thanks for all your replies. I tried printing out the value of 1.0, packed as a float, then unpacked in hex. I got the value 0000803f. Then I tried the same with the encoded value sent from my application, and got 3f800000. This looked like it could be the little endian/big endian problem, so I tried the suggested conversion
unpack "f*", pack "N*", unpack "V*", $_[0];
which did the trick. I have one last query - does the order of the bits matter as to whether the format qualifies as a IEEE 754 floating point number? This is quite a concern, as the application that was causing the trouble is a test suite for a particular standard (which specified IEEE 754 as the floating point format), so I don't want to code to this application if it is wrong!

Once again, thank you for all your suggestions.

Replies are listed 'Best First'.
Re: Re: Extracting IEEE 754 floating point numbers
by Thelonius (Priest) on Oct 29, 2002 at 12:50 UTC
    Does the order of the bits matter as to whether the format qualifies as a IEEE 754 floating point number?
    No, but when sent between machines they should be stored in network byte order, which is what the application did.
Re: Re: Extracting IEEE 754 floating point numbers
by jmcnamara (Monsignor) on Oct 29, 2002 at 13:27 UTC

    I have one last query - does the order of the bits matter as to whether the format qualifies as a IEEE 754 floating point number?

    Both systems are valid since the IEEE754 specification doesn't state which order the bytes should be in. And just to clarify, it is the bytes that are reordered not the bits. ;-)

    --
    John.

Re: Re: Extracting IEEE 754 floating point numbers
by physgreg (Scribe) on Oct 29, 2002 at 14:34 UTC
    Great! Thanks for the clarification - I feel a lot happier now. I also found the same issue with double precision numbers, but in this case I had to do a 'reverse' on the input (as per a previous suggestion), as there was no applicable unpack format that would work.

Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: note [id://208692]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others about the Monastery: (4)
As of 2022-08-13 10:15 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found

    Notices?