Functional Programming 👷🏼‍♂️👷🏼‍♀️

Overview

First Class Functions

• functions can be used as inputs and outputs of other functions
• functions can be assigned to variables and can be stored in collections
• can perform all the operations on functions that you can do with values of other types

Higher-Order Funcions

• takes other functions as arguments, or returns them as results

Avoiding state mutation

• once created an object never changes

Pure functions

• no side effects (no memory external to function is modified, no I/O, no exceptions thrown)
• when called with same values will always return the same result

Closure

• a function passed around along with it's environment

Currying

• evaluating multiple arguments of a function, one by one, producing intermediate results

f(x,y) = x + y
f(3,4) = 3 + 4

substituting for x we get
f(3, y) = 3 + y

Define g(y) as g(y) = 3 + y then following is true:
f(3,y) = g(y) = 3 + y