I'm making a calculator app using DDMathParser. The problem I'm facing is sin(pi()) doesn't return 0 but a trivial number like 1.2246...e-16. I'm just wondering is there any way to convert it to 0?
Thank you.
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No need for DDMathParser for that. Just use `sin(M_PI);`. – rmaddy Jan 30 '15 at 04:52
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I'd like to convert any input expressions into a double value, so it's by far easier to write if I use a math parser. – user Jan 30 '15 at 06:00
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The -description method on NSNumber does not accurately represent the underlying number:
NSLog(@"%f", sin(M_PI)); // logs 0.000000
NSLog(@"%@", @(sin(M_PI))); // logs 1.224646799147353e-16
To work around this, you can pull out the -doubleValue of the NSNumber, and that should give you 0:
NSLog(@"%f", @(sin(M_PI)).doubleValue); // logs 0.000000
Dave DeLong
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You are cheating here: `M_PI` is not exactly π, and therefore `sin(M_PI)` is not exactly zero. `NSLog(@"%f", sin(M_PI))` logs 0.000000 because it rounds to a precision of 6 decimal digits, not because it is "more accurate" than the description method of NSNumber. – Martin R Jul 16 '16 at 21:13