The func keyword in the context of a structure indicates that this is a method. It takes a single parameter of type Double and returns an instance of Vector.
Hillegass, Aaron; Preble, Adam; Chandler, Nate (2015-04-16). Cocoa Programming for OS X: The Big Nerd Ranch Guide (5th Edition) (Big Nerd Ranch Guides) (Kindle Locations 1693-1695). Pearson Education. Kindle Edition.
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The func keyword in the context of a structure indicates that this is a method. It takes a single parameter of type Vector and returns an instance of Vector.