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Re: IV preservation (was Re: [PATCH 5.7.0] compiling on OS/2)

From:
Ilya Zakharevich
Date:
February 17, 2001 11:57
Subject:
Re: IV preservation (was Re: [PATCH 5.7.0] compiling on OS/2)
Message ID:
20010217145735.B26498@math.ohio-state.edu
On Sat, Feb 17, 2001 at 05:14:25PM +0000, nick@ing-simmons.net wrote:
> >>        The frexp() function is used to split the number x into  a
> >>        normalized  fraction  and  an  exponent which is stored in
> >>        exp.              
> >
> >I would not think that this has anything to do with the bitpattern
> >manipulations you described above.
> 
> Sure it is.
> frexp() says extract the exponent and stuff it in the integer provided,
> then set the exponent to 0 and return the resulting double which is 
> now the fraction.

But you are back where you were: how do you extract the bitpattern
from the "normalized fraction" part?

> Strictly speaking true. But as "minimum" float and double ranges
> fit in exactly 32 and 64 bits respectively, with the 
> sign, exponent, (hidden MSB), mantissa as per IEEE then in practice the 
> only difference is big/little endian style ordering of the fields.

I have some vague recollections that it is not always as simple as
that, even with 32b and 64b IEEE...

Ilya



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