Re: Identifying an exact binary representation

On Feb 3, 6:28 pm, "Bernhard Enders" <bgen...@xxxxxxxxx> wrote:
Does anybody know of a Fortran (can be Java also) procedure that is
able to identify if a given floating point number has an exact binary
representation? Is there a simple algorithm for this task that I am
missing? Thanks in advance,

Bernhard.

You'd have to start out with the decimal representation, as has been
pointed out, but couldn't youdo something like this:

Suppose the decimal representation is ".1234". Move the decimal point
to right till you have a decimal integer. Integers never get rounded
on conversion to floats. Then just compare 1234. with .1234*10**4. If
they are unequal, then clearly .1234 got rounded. This obviously only
works within a certain range, but depending on your application that
may be ok.

I must say I have an odd feeling about this suggestion - there are a
lot of smart people in this newsgroup and I wonder they are missing
something - or I am!

Daniel Feenberg

.

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