Double increment from negative to positive in for loop

Asked May 19 '14 at 09:07

Active May 19 '14 at 09:16

Viewed 639 times

I executed the below for loop,

for(double i = -1.0;i <=1.0;i=i+0.1)
      System.out.println(i);

O/P:

-1.0
-0.9
-0.8
-0.7000000000000001
-0.6000000000000001
-0.5000000000000001
-0.40000000000000013
-0.30000000000000016
-0.20000000000000015
-0.10000000000000014
-1.3877787807814457E-16
0.09999999999999987
0.19999999999999987
0.2999999999999999
0.3999999999999999
0.4999999999999999
0.5999999999999999
0.6999999999999998
0.7999999999999998
0.8999999999999998
0.9999999999999998

In the middle before 0.0 getting a weird -1.3877787807814457E-16.

There is no exact representation of the decimal points in binary, but there should be a relevance. This -1.3877787807814457E-16 does not related to any values between -0.1 to 0.0.

why this value is computed ?

edited May 19 '14 at 09:16

asked May 19 '14 at 09:07

user1894220

1

Don't you ever use `double` in loops. – Maroun May 19 '14 at 09:08
Related: http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html – sp00m May 19 '14 at 09:09
ya i agree. But why this middle value? just out of curiosity. – user1894220 May 19 '14 at 09:09
It's E notation - basically it means -1.3877787807814457 x 10^(-16). Basically a very small number. – Evan Knowles May 19 '14 at 09:11
You have an accumulated error and -0.10000000000000014 + 0.1 is -1.4e-16 so that is perhaps the least surprising number in your list ;) – Peter Lawrey May 19 '14 at 10:02

Double increment from negative to positive in for loop

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