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## Is this a numerical problem?

 From: Lukas Reichlin Subject: Is this a numerical problem? Date: Thu, 19 Aug 2010 10:39:45 +0200

```Dear Octave community

I'm using Octave 3.2.4 from MacPorts on MacOSX 10.6.4 running on an Intel Core
2 Duo. I noticed a behaviour which seems strange to me. Does someone have a
good explanation for the results below?

octave:60> a = (10 * rem (-12/5, 1))
a = -4.00000000000000  # a < -4
octave:61> fix (a)
ans = -3  # I'm expecting -4
octave:62> a + 4
ans =  8.88178419700125e-16  # I'm expecting something negative

# While this is working as expected
octave:63> b = -4.001
b = -4.00100000000000
octave:64> fix (b)
ans = -4
octave:65> b + 4
ans = -0.00100000000000033

The same with R2009a:

>> a = (10 * rem (-12/5, 1))

a =

-4.0000

>> fix (a)

ans =

-3

>> a+4

ans =

8.8818e-16

>> b = -4.001

b =

-4.0010

>> fix (b)

ans =

-4

>> b + 4

ans =

-0.0010

>>

Best Regards,
Lukas

```

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