Swift Programming: The Big Nerd Ranch Guide

Functional Programming

Swift adopts some patterns from the functional programming paradigm. It is difficult to provide a concrete definition of functional programming because people use the phrase with different meanings and intentions, but typically it is understood to include:

• First-class functions – functions can be passed as arguments to other functions, can be stored in variables, etc.; they are just like any other type.

• Pure functions – functions have no side effects; functions, given the same input, always return the same output, and do not modify other states elsewhere in the program. Most math functions like sin, cos, fibonacci, and factorial are pure.

• Immutability – mutability is de-emphasized as it is more difficult ...