Can anybody figure out how the following statement evaluates to 7?
echo (int)( (0.1+0.7)*10 );
I was trying the operator precedence in PHP. So, if there is anybody who can help, it will be highly appreciated.
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0.1 != 0.1 as we know it.. [tony the pony](http://msmvps.com/blogs/jon_skeet/archive/2009/11/02/omg-ponies-aka-humanity-epic-fail.aspx) – Michael Kunst Aug 14 '13 at 17:23
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http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems – Mark Baker Aug 14 '13 at 17:37
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If you remove the (int) part, and run the follwing code instead:
echo number_format(((0.1+0.7)*10), 20);
The output will be 7.99999999999999911182. This value parsed to an integer will result to 7, as parsing a value to an integer will always floor the value.
Reading the following article should give you an idea of what's going on here.
In short, double values are always a binary value, and through that a 'product of 2^n', whichever will be the nearest to the decimal you said it should be. And with 2^n you dont have any chance to reach exactly 0.1.
Michael Kunst
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Pony story puts a smile on my face and is complete true. And some extra proof printf("%b", (0.1+0.7)*10); // 111 binary 7 decimal – Raymond Nijland Aug 14 '13 at 17:47