Question

I am trying to run my program and i am using

double result = cos(90*M_PI/180);
NSLog("Cos 90 value %g",result);  //Prints 6.12323e-17

But when i run this

 NSLog("Cos 90 value %f",cos(90*M_PI/180)); //Prints 0

I want to get value of cos90 in result(double) which should be 0.I know thats floating point airthmetic issue.But how to solve it.Is there any way to do it?

Thanks

Answer 1

Lastly I found solution.All the explanation are right but “temporary” solution to this problem is with NSNumberFormatter.

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];

[formatter setAlwaysShowsDecimalSeparator:NO];
[formatter setAllowsFloats:YES];
[formatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
[formatter setMinimumFractionDigits:0];
[formatter setMaximumFractionDigits:10]; //THIS IS IMPORTANT AS AFTER DECIMAL, DIGITS SHOULD BE LESS THAN 17 because there is difference of 6.12323e-17 

double result = cos(90*M_PI/180);
NSNumber *numberResult = [NSNumber numberWithDouble:result];

[formatter setNumberStyle:NSNumberFormatterDecimalStyle];
NSLog(@"%@",[formatter stringFromNumber:number]); //Prints 0

It’s a temporary solution.You can also prints value of cos 90 with %f but it will also prints unwanted six 0 after decimal.