I just ran into a peculiar problem in PHP. What should this result in?
floor(100 * (5.8 - floor(5.8)))
This should equal 80, but I keep getting 79, which is obviously wrong. Any suggestions? Does anyone have the same problem?
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Lars Ebert
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7Welcome to floating point math – John Conde Jun 12 '14 at 15:45
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2See also: http://floating-point-gui.de/basic/ – Amal Murali Jun 12 '14 at 15:46
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3Also happens in javascript: put Math.floor(100 * (5.8 - Math.floor(5.8))) into your console. See http://stackoverflow.com/questions/4502588/doing-exact-real-number-arithmetic-with-php for possible solutions. – Kris Erickson Jun 12 '14 at 15:46
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1Everyone has the same problem, floating point math is imprecise. – TJHeuvel Jun 12 '14 at 15:49
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1Don't take the floor of your result. Just leave it at `100 * (5.8 - floor(5.8))`. It might not be practical for your application, but it will return 80. – dcclassics Jun 12 '14 at 15:58
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5.8 was just an example in this case, the target was to get exactly two decimal digits from a float – Lars Ebert Jun 12 '14 at 15:59