[Haskell-beginners] How to improve the accuracy of floating point calculation?

[David McBride]

Use rationals and then convert to float.  Ie:

> [0.1::Rational,0.2..2]
[1 % 10,1 % 5,3 % 10,2 % 5,1 % 2,3 % 5,7 % 10,4 % 5,9 % 10,1 % 1,11 % 10,6
% 5,13 % 10,7 % 5,3 % 2,8 % 5,17 % 10,9 % 5,19 % 10,2 % 1]

Then to get something useful from it:

> map fromRational $ [0.1::Rational,0.2..2]
[0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0,1.1,1.2,1.3,1.4,1.5,1.6,1.7,1.8,1.9,2.0]

On Tue, Feb 5, 2013 at 5:41 PM, yi lu <zhiwudazhanjiangshi at gmail.com> wrote:

> Hi,
>
> I found that in ghci, I input
> [0.1,0.2..2]
> and run, I get a result of
>
>
> [0.1,0.2,0.30000000000000004,0.4000000000000001,0.5000000000000001,0.6000000000000001,0.7000000000000001,0.8,0.9,1.0,1.1,1.2000000000000002,1.3000000000000003,1.4000000000000004,1.5000000000000004,1.6000000000000005,1.7000000000000006,1.8000000000000007,1.9000000000000008,2.000000000000001]
>
> But, as you know, it is not the exact answer.
>
> So, I wonder if there is something I can do to achieve a better
> performance and get [0.1,0.2,0.3,0.4..] as the result.
>
> Thanks.
>
> _______________________________________________
> Beginners mailing list
> Beginners at haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/beginners/attachments/20130205/5bb5d75a/attachment.htm>