Functional Programming

First class functions

• passing functions as arguments to other functions
• returning functions as the values from other functions
• assigning functions to variables or storing them in data structure
• anonymous function / lambdas

Pure functions

• same output for same function arguments/inputs.
• no side effects

Higher order functions

• function that takes one or more functions as arguments or
• returns a function as its result

Closure & state capturing

• technique for implementing lexically scoped name binding in a language with first class functions
• combination of a function bundled together with references to its surrounding state.

func get_me_closure(v int) func(int) bool {
    return func(x int) bool {
        return v == x
    }
}

Function currying

• technique of translating a function that takes multiple arguments into a sequence of families of function, each taking a single argument
• eg. option pattern