The 60s called

And they have some ideas for your code.

Presented by: Dave Smith

In the 60's, some people were working
to shape the future of computing.

Some people weren't.

Keep this in mind...

Lisp ... has assisted a number of our most gifted fellow humans in thinking previously impossible thoughts.

- Edsger Dijkstra, 1972

ancient Concepts You use today

  • Garbage Collection
  • First Class Functions
  • Closures

garbage collection

Invented in 1959 by John McCarthy to improve Lisp

Before Garbage Collection

void my_function() {
char *data = malloc(1024);
return; // oops! memory leak

After Garbage Collection

function my_function() {
var data = [1, 2, 3, 4, ..., 1024];
return; // data will be freed later

First class Functions

Defined by  Christopher Strachey in the mid-1960's.

Example 1: Function Returning a Function

function counter() {
var n = 0;
return function() {
return n;
c = counter();
c(); // returns 1
c(); // returns 2

Example 2: Function as Argument

$("button").click(function(event) {
// handle the click

Example 3: Storing Functions in Data Structures

var handlers = [
function() { ... },
function() { ... }
var thingsToRun = {
red: function() { ... },
blue: function() { ... },
green : function() { ... }

Example 4: Storing data structures on functions?

function Thing() { = "Bob"; = [1138, 42, 1701];

var thing = new Thing();


Peter J. Landin defined the term in 1964

Closure Definition:

  1. A reference to a function
  2. With the enclosing environment

Closure Example:

(function () {
var name = "Bob, the Closure String";
$("button").click(function() {
alert("My closure has a name variable: " + name)
IIFE's are closures!

JavaScript developers use closures more than
any other developer community I've seen.

Some examples:

Garbage Collection


First Class Functions




Very Productive Programming

lesser known* ancient concepts

  • Referential Transparency
  • Function Composition
  • Lazy Evaluation
  • Immutability

* Warning: Subjective statement.

Referential Transparency

Defined by Christopher Strachey in 1967

a.k.a. The philosophy that contributes to React's speed.

Definition of Referential Transparency

The ability to replace a function with its return value.

Every mathematical expression is referentially transparent

I can write:


or I can write:


They are equivalent.

Side note: OS X Spotlight is nifty

How React uses referential transparency

To put it more mathematically:

function composition

Applying functions to the result of functions 

Maybe popularized by Haskell Curry  in the 1960s?

See also: Currying

The mathy version:


Without Composition

function capitalize(list) {
for (var i=0; i<list.length; i++) {
list[i] = list[i].toUpperCase();

Not composable because:
  1. No return value
  2. Mutates the input list

With Composition

function upper(str) {
return str.toUpperCase()
function capitalize(list) {

  1. Can be chained with other functions
  2. Referentially transparent
  3. Easily testable

Promises use composition:


What does  then() return?

lazy evaluation

Invented for computer programming in 1976


Delay the evaluation of an expression until it is needed


  • Performance wins
  • Construct infinite data sets

Example: Expensive CPU operation

Eager evaluation:
function findNextPrime(previousPrime) {
// do lots of work
return nextPrime;

Lazy evaluation:
function findNextPrime(previousPrime) {
return function() {
// do lots of work
return nextPrime;

The caller decides when (or if) to actually do the work.

JavaScript has weak built-in support for lazy evaluation

But Python's support is awesome:

translated_string = trans("Hello, world!") 

The variable "translated_string" will not get translated until the first time someone tries to read its value.


Don't know when this concept was invented.

But it was probably Lisp.

Everything is Lisp.


Definition of immutability:

Objects can be created, but not altered.

var x = {name: "Bob"}; = "Fred"; // Not allowed!

Benefits of immutable data:

  • More easily testable
  • Easier concurrency
  • No side effects
  • Easier flyweights

JavaScript strings are immutable

Most string methods return new strings.

JavaScript has no enforcement for immutable objects.

Or does it...

Whoa. Object.freeze()


OTher concepts from ANTIQUITY

  • Tail recursion
  • Side effects
  • Pure functions

The 60's gave us functional programming.

The 60's are coming back

"Boundaries" by Gary Bernhardt

Why functional programming is on the rise

The 60's in modern languages

Visual F#

The 60's were awesome

The 60's called

By djsmith

The 60's called

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