Shoutbox

I have to add 0.1 to a number and keep doing it... but I get some wierd results =/

quote:

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Script has been stopped
Script is starting
Script is now loaded and ready
(!) 0.1
(!) 0.2
(!) 0.30000000000000004
(!) 0.4
(!) 0.5
(!) 0.6
(!) 0.7
(!) 0.7999999999999999
(!) 0.8999999999999999
(!) 0.9999999999999999
(!) 1.0999999999999998
(!) 1.2

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Why is this? :s


EDIT:

A for loop causes this:

code:

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    for(var x=0;x<10;x+=y){
        Debug.Trace(x);
    }

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quote:

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Script has been stopped
Script is starting
Script is now loaded and ready
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
5
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.99999999999999
6.09999999999999
6.19999999999999
6.29999999999999
6.39999999999999
6.49999999999999
6.59999999999999
6.69999999999999
6.79999999999999
6.89999999999999
6.99999999999999
7.09999999999999
7.19999999999999
7.29999999999999
7.39999999999999
7.49999999999999
7.59999999999999
7.69999999999999
7.79999999999999
7.89999999999999
7.99999999999999
8.09999999999999
8.19999999999999
8.29999999999999
8.39999999999999
8.49999999999999
8.59999999999999
8.69999999999999
8.79999999999998
8.89999999999998
8.99999999999998
9.09999999999998
9.19999999999998
9.29999999999998
9.39999999999998
9.49999999999998
9.59999999999998
9.69999999999998
9.79999999999998
9.89999999999998
9.99999999999998

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how is y made up?
maybe y != 0.1 but y == 0.0999999999999999999999
try a Debug.Trace(1000000000000 * y)

just an idea, don't know if it will do any good

edit: though that won't explain the

quote:

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(!) 0.30000000000000004

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y is definately 0.1

I'm testing the for loop with static variables

http://en.wikipedia.org/wiki/Floating_point

This is because whatever programming language and data type you use treats your numbers as IEEE floats.  Floats are not exact by their nature; the linked article should explain why not.  If you are going to use floats you should remember to code your program logic to never do exact comparisons -- only "greater than" or "less than". 

If this is not acceptable, there are a few options.  Your programming language may offer a built-in BCD (binary coded decimal) type or there may be a suitable free or commercial class available.  If you are doing fixed point math, such as dealing with money, you can simply use integer types and represent the values using the smallest base unit (e.g. 115 cents instead of $1.15).

quote:

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Originally posted by Adeptus
If you are doing fixed point math, such as dealing with money, you can simply use integer types and represent the values using the smallest base unit (e.g. 115 cents instead of $1.15).

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My best bet I think ty

I confirm what Adeptus said.

I found away around it now, thanks for everyones help