Using trig functions in Swift

Question

Apple offers a bunch of functions from a file called 'math.h' containing, you guessed it, math stuff. Among these are trigonometric functions such as sin() and cos().

But, of course, there's a problem when it comes to the tangent function, tan(). It takes in a Double and returns a Double, in radians, but because of a mathematical property to which I am already aware, Swift returns an error if you write tan(M_PI / 2) (M_PI is a constant for pi in the same file), rather than returning nil.

I myself won't program this specifically, but it may be tried by a user of my program. Does anyone know how I could safely wrap this result and present it to the user without crashing my app?

Answer 1 · 2015-12-27T05:27:06Z

December 27, 2015 5:27am

Your math.h providing your tan function is imported along with Foundation. It is old, from way back in the Darwin days. :)

Consider the following code:

import Foundation

let result = tan(M_PI / 2)  // Returns 1.633123935319537e+16

The header shows this:

 #include <math.h>

 double
 tan(double x);

 long double
 tanl(long double x);

 float
 tanf(float x);

So in the case of the code above, taking in M_PI as a double returns result as a double.

Perhaps you are needing a long or a float?

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Joshua Rapoport

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Using trig functions in Swift

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Nathan Tallack

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