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Re: decimal to binary?

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Bryan R Harris
September 23, 2009 17:37
Re: decimal to binary?
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>>>>>> "BRH" == Bryan R Harris <> writes:
>   BRH> Maybe this is just my own ignorance on big-endian vs. little endian,
> but
>   BRH> this code:
>   BRH>   print "big-endian:     ", unpack("H*", pack("d", -3205.0569059)),
> "\n";
>   BRH>   print "little-endian:  ", unpack("h*", pack("d", -3205.0569059)),
> "\n";
>   BRH> prints:
>   BRH>   big-endian:     e626c5221d0aa9c0
>   BRH>   little-endian:  6e625c22d1a09a0c
> note that those are the same bytes but each byte is printed with
> different ordering for the hex digits.
> the docs say this:
>                    h   A hex string (low nybble first).
>                    H   A hex string (high nybble first).
> and a nybble (or nibble) is a single hex digit of 4 bits and there are
> two in a byte. the h vs H only changes the nibble order in a byte. this
> has nothing to do with endian issues which are a byte ordering thing.
> pack doesn't have a direct way to deal with endians with floats. you can
> just use reverse on the byte string to control that. that is what i do
> in Sort::Maker for this. did you look at that module yet? as i keep
> saying it does exactly what you are trying to do so you can learn from it.

Ah, this is the key I was missing!  Thanks.  Now I'm getting this:

value:  -3205.0569059
      big-endian:     c0 a9 0a 1d 22 c5 26 e6
      little-endian:  e6 26 c5 22 1d 0a a9 c0

I'm not sure whether I have my endians switched, but I'm putting my chances
of being right here at a little better than 50%.  =)  (Actually, I see your
$IS_BIG_ENDIAN check at the beginning of Sort::Maker, and borrowing that, I
think my chances are much better now that I got it right.)

As for looking at Sort::Maker, I have to admit I was a little scared at
first.  It's not obvious to me why you'd need to be packing doubles for a
sort routine, and I feared I'd get lost in the code...  That said, I found
the reverse part and it looked easy, so that's what I needed.

I think I'm good.  Thanks again to all.  Hope this makes good list-archives

- Bryan

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