From: Axel Friedrich <lists@...>
Date: 2012-12-10T23:58:16+09:00
Subject: Re: Binary Fixed-Point in Ruby? (Improved FixedPt?)

Unfortunatly, I don't understand how BigDecimal could help with my
Binary- Fixed-Point problems.

Maybe I should explain in more details:

I have _no_ problem with accuracy.
I'm developing hardware, which calculates mathematic expressions using
"fixed-point binary representations" of values. That is a certain number
of bits (say 16) represent a value (say 0.1). The format of the
fixed-point representation must "set" right (right number of bits and
right place of the virtual binary point), in order to avoid overflow or
loss of accuracy. For checking, if I have "set" the format right, I want
to simulate it in Ruby. Normaly, Ruby does it's calculations in Integer,
or Double or even BigDecimal, but not in BINARY Fixed-Point, so I think
I must use a special library for this, for example the existing
"FixedPt"-library. But unfortunately, this library is not perfect enough
for my purpose.

Maybe this explains it better:
http://en.wikibooks.org/wiki/Floating_Point/Fixed-Point_Numbers

Axel


Bartosz Dziewoński wrote in post #1088523:
> There is BigDecimal in the standard library.
>
> irb(main):011:0> require 'bigdecimal'
> => true
> irb(main):012:0> BigDecimal
> => BigDecimal
> irb(main):014:0> BigDecimal.new '123'
> => #<BigDecimal:13c0950,'0.123E3',9(18)>
>
> http://www.ruby-doc.org/stdlib-1.9.3/libdoc/bigdecimal/rdoc/index.html
>
> -- Matma Rex

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