# Any body can help me ? why is this happen?

Hii All

I use ruby 1.8.7
I run irb and type:

a = (0.29 * 100).to_i

the result is 28

why???

could u explain to me… Please???

THank you

Senior Rails Developer
Anton Effendi - Wu You Duan

Scary!

irb(main):019:0> (0.57 * 100).to_i
=> 56
irb(main):020:0> (0.58 * 100).to_i
=> 57

This is totally out of my understanding… Will look into core… seems
like some bug…

Nm… this explains it:

http://rubypond.com/blog/when-ruby-floating-just-isn-t-good-enough

(0.29*100).to_s.to_i will return what you expect.

Quoting anton effendi [email protected]:

Hii All

I use ruby 1.8.7
I run irb and type:

a = (0.29 * 100).to_i

the result is 28

Here’s why:

irb(main):008:0> ‘%0.16f’ % (0.29 * 100)
=> “28.9999999999999964”

Most decimal fractions cannot be represented exactly in binary. If you
need
them to behave in certain ways, e.g. using real numbers to represent US
dollars and cents, take care and learn to use the following functions as
needed.

irb(main):002:0> (0.29 * 100).to_i
=> 28
irb(main):003:0> (0.29 * 100).round
=> 29
irb(main):004:0> (0.29 * 100).floor
=> 28
irb(main):005:0> (0.29 * 100).ceil
=> 29
irb(main):009:0> (-0.29 * 100)
=> -29.0
irb(main):010:0> (-0.29 * 100).to_i
=> -28
irb(main):011:0> (-0.29 * 100).floor
=> -29
irb(main):012:0> (-0.29 * 100).round
=> -29
irb(main):013:0> (-0.29 * 100).ceil
=> -28

IIRC, .to_i rounds towards zero, .floor rounds down, .ceil rounds up,
and
.round adds 1/2 and rounds towards zero.

HTH,
Jeffrey

P.S. if you are in the financial field, the SEC has rules on how to do
arithmetic in US dollars and cents.

See this may be u get some idea…
http://rubypond.com/blog/when-ruby-floating-just-isn-t-good-enough

-Shyam

Thank you all
I found why that happen…

On Wed, Mar 31, 2010 at 11:39 PM, Jeffrey L. Taylor
[email protected]wrote:

Here’s why:
irb(main):002:0> (0.29 * 100).to_i
=> -28

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