Table of Contents Overview Functional anonymous first-class usual definition high-order first-order

Name	Typing		Type-checking		Functional
Name	Static	Dynamic	Strong	Weak
JavaScript	_	X	_	X	X
Python	_	X	X	_	X
Perl	X (use strict)	X	X	_	X
Java	X	_	X	_	X

An anonymous function (function literal, lambda abstraction, or lambda expression) is a function definition that is not bound to an identifier.

Do with functions what you can do with primitive types

• create it ?
• pass it as an argument
• return it

PL have first-class functions if it treats functions as first-class citizens.
A first-class citizen (also type, object, entity, or value) in a given programming language is an entity which supports all the operations generally available to other entities. These operations typically include being passed as an argument, returned from a function, modified, and assigned to a variable.

In mathematics and computer science, a higher-order function is a function that does at least one of the following:

• takes one or more functions as arguments (i.e. procedural parameters),
• returns a function as its result.
  

A functions that operate on functions.

const twice = (f, v) => f(f(v));
const add3 = v => v + 3;
twice(add3, 7); //  ((7 + 3) + 3) = 13

All functions, but high-order, are first-order functions