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From: Jan Burse <janburse@fastmail.fm>
Newsgroups: comp.lang.java.programmer
Subject: Re: Fixed-point arithmetic library
Date: Wed, 22 Feb 2012 22:59:45 +0100
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If a decimal scale suits you, you could use:

http://docs.oracle.com/javase/7/docs/api/java/math/BigDecimal.html

Decimal scale means your numbers would be represented as:

      mantissa * 10 ^ -scale

Bye

Tom Anderson schrieb:
> Evening all,
>
> I would quite like to represent some numbers in fixed point, and do
> arithmetic with them.
>
> These numbers will mostly not be more than a bilion, and will probably
> never be more than a hundred billion. Some of them, i will need to
> represent to eight decimal places. I'd like to be able to multiply two
> large numbers, but i suspect will not need to multiply three. 11 * 2 + 8
> = 30 decimal digits; that's about 100 bits, so 128 bits would be big
> enough (about 5 decimal digits of headroom).
>
> Can anyone suggest an existing library for doing fixed-point arithmetic
> which would cover this?
>
> I have googled, but not found anything. There are a few fixed-precision
> libraries aimed at J2ME (i assume because old phones didn't have
> floating-point units?). There's something called jExigo, but it's 64-bit
> and the code doesn't look great.
>
> It's quite possible that there is no such library. But i thought it
> prudent to ask before writing one myself.
>
> Thanks,
> tom
>