Floating point calculation problem

ruby-talk
1

hi.
i'm confused by float point calculation.
like this!

···

------------------------------------------
irb(main):001:0> 123.6 - 123
=> 0.599999999999994

------------------------------------------

how to i get result 0.6 ?
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Posted via http://www.ruby-forum.com/.

2

Hi,

hi.
i'm confused by float point calculation.
like this!

------------------------------------------
irb(main):001:0> 123.6 - 123
=> 0.599999999999994

------------------------------------------

how to i get result 0.6 ?

try using BigDecimal, like:

irb(main):001:0> require 'bigdecimal'
=> true
irb(main):002:0> x = BigDecimal("123.6") - BigDecimal("123")
=> #<BigDecimal:8b13c,'0.6E0',4(16)>
irb(main):003:0> x.to_f
=> 0.6

zoran

···

On Tue, Jul 8, 2008 at 10:39 AM, Hyun chul Park <paxcholy@gmail.com> wrote:
--
Human by day user by night

3

-------- Original-Nachricht --------

Datum: Tue, 8 Jul 2008 17:39:50 +0900
Von: Hyun chul Park <paxcholy@gmail.com>
An: ruby-talk@ruby-lang.org
Betreff: Floating point calculation problem

Hi --

hi.
i'm confused by float point calculation.
like this!

------------------------------------------
irb(main):001:0> 123.6 - 123
=> 0.599999999999994

------------------------------------------

how to i get result 0.6 ?

you may want to take a look at this:

http://docs.sun.com/source/806-3568/ncg_goldberg.html

If you want to do exact calculations, you can use fractions

http://www.ruby-doc.org/stdlib/libdoc/rational/rdoc/classes/Rational.html

To convert between the two, for each real number (Float), you can use its continued fraction
approximation.

Here's a link to a Ruby program that calculates digits of Pi from its continued fraction representation
(and also a Java one, which is much longer):

http://www.cs.utsa.edu/~wagner/pi/pi_cont.html

Best regards,

Axel

···

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4

Zoran Regvart wrote:

Hi,

how to i get result 0.6 ?

try using BigDecimal, like:

irb(main):001:0> require 'bigdecimal'
=> true
irb(main):002:0> x = BigDecimal("123.6") - BigDecimal("123")
=> #<BigDecimal:8b13c,'0.6E0',4(16)>
irb(main):003:0> x.to_f
=> 0.6

zoran

thank you, you're reply.

···

On Tue, Jul 8, 2008 at 10:39 AM, Hyun chul Park <paxcholy@gmail.com> > wrote:

--
Posted via http://www.ruby-forum.com/\.