tour guide : Yan Cui @theburningmonk

Hi, my name is Yan Cui.

1MILLION USERS
ACTIVE
DAILY

250MILLION DAY
PER
REQUEST

agenda

Type Provider Pipes
Statically Resolved TP
Implicit Interface
Implementation
Borrowed Pointers Dependent Types
Uniqueness Types
Bit Syntax
Signals
Macros
Unit-of-Measure
Actor Model

F#
ClojureErlang
Go
RustElm Idris

F#
ClojureErlang
Go
RustElm Idris

disclaimers

“Programming languages
have a devious influence:
they shape our thinking
habits.”
- Edsger W. Dijkstra

“One of the most disastrous
thing we can learn is the first
programming language, even
if it's a good programming
language.”
- Alan Kay

“The limits of my
language means the limits
of my world.”
- Ludwig Wittgenstein

“We cannot solve our
problems with the same
thinking we used when
we created them.”
- Albert Einstein

F#
ClojureErlang
Go
RustElm Idris

your
app

your
app
CSVCSVCSV
CSVCSVXML

your
app
CSVCSVCSV
CSVCSVXML
some
service

your
app
CSVCSVCSV
CSVCSVXML
some
service
DB

1. define DTO types!
2. I/O!
3. marshal data into DTO!
4. do useful work

1. define DTO types!
2. I/O!
3. marshal data into DTO!
4. do useful work

compiler
provideexternal
data source typed info

type providers

intellisense!
tooltips!
…

compile time validation

no code generation

R
FunScript
Azure
Amazon S3
CSVSQLite
SQL Server
WSDL
WorldBank
Regex
ODATA IKVM
Facebook
Apiary
XAMLFreebaseHadoop
Oracle
Minesweeper
Don Syme
Powershell
JSON
Fizzbuzz
Mixin
RSS
Matlab
Dates
NorthPole
XML
Python

pipes

“…a clean design is one that
supports visual thinking so
people can meet their
informational needs with a
minimum of conscious effort.”
- Daniel Higginbotham
(www.visualmess.com)

Whilst talking with an ex-colleague, a question came up on how to implement the Stable Marriage
problem using a message passing approach. Naturally, I wanted to answer that question with Erlang!!
!
Let’s first dissect the problem and decide what processes we need and how they need to interact with
one another.!
!
The stable marriage problem is commonly stated as:!
Given n men and n women, where each person has ranked all members of the opposite sex with a
unique number between 1 and n in order of preference, marry the men and women together such that
there are no two people of opposite sex who would both rather have each other than their current
partners. If there are no such people, all the marriages are “stable”. (It is assumed that the participants
are binary gendered and that marriages are not same-sex).!
From the problem description, we can see that we need:!
* a module for man!
* a module for woman!
* a module for orchestrating the experiment!
In terms of interaction between the different modules, I imagined something along the lines of…
how we read ENGLISH
see also http://bit.ly/1KN8cd0

Whilst talking with an ex-colleague, a question came up on how to implement the Stable Marriage
problem using a message passing approach. Naturally, I wanted to answer that question with Erlang!!
!
Let’s first dissect the problem and decide what processes we need and how they need to interact with
one another.!
!
The stable marriage problem is commonly stated as:!
Given n men and n women, where each person has ranked all members of the opposite sex with a
unique number between 1 and n in order of preference, marry the men and women together such that
there are no two people of opposite sex who would both rather have each other than their current
partners. If there are no such people, all the marriages are “stable”. (It is assumed that the participants
are binary gendered and that marriages are not same-sex).!
From the problem description, we can see that we need:!
* a module for man!
* a module for woman!
* a module for orchestrating the experiment!
In terms of interaction between the different modules, I imagined something along the lines of…
2.top-to-bottom
1.left-to-right
how we read ENGLISH
see also http://bit.ly/1KN8cd0

how we read CODE
public void DoSomething(int x, int y)!
{!
Foo(y,!
Bar(x,!
Zoo(Monkey())));!
}
see also http://bit.ly/1KN8cd0

how we read CODE
public void DoSomething(int x, int y)!
{!
Foo(y,!
Bar(x,!
Zoo(Monkey())));!
}
2.bottom-to-top
1.right-to-left
see also http://bit.ly/1KN8cd0

Whilst talking with an ex-colleague, a question came up on
how to implement the Stable Marriage problem using a
message passing approach. Naturally, I wanted to answer
that question with Erlang!!
!
Let’s first dissect the problem and decide what processes we
need and how they need to interact with one another.!
!
The stable marriage problem is commonly stated as:!
Given n men and n women, where each person has ranked
all members of the opposite sex with a unique number
between 1 and n in order of preference, marry the men and
women together such that there are no two people of
opposite sex who would both rather have each other than
their current partners. If there are no such people, all the
marriages are “stable”. (It is assumed that the participants
are binary gendered and that marriages are not same-sex).!
From the problem description, we can see that we need:!
* a module for man!
* a module for woman!
* a module for orchestrating the experiment!
In terms of interaction between the different modules, I
imagined something along the lines of…
2.top-to-bottom
1.left-to-right
how we read ENGLISH
public void DoSomething(int x, int y)!
{!
Foo(y,!
Bar(x,!
Zoo(Monkey())));!
}
2.top-to-bottom
1.right-to-left
how we read CODE
see also http://bit.ly/1KN8cd0

“…a clean design is one that
supports visual thinking so
people can meet their
informational needs with a
minimum of conscious effort.”

|>

how we read CODE
let drawCircle x y radius =
radius |> circle
|> filled (rgb 150 170 150)
|> alpha 0.5
|> move (x, y)
see also http://bit.ly/1KN8cd0

how we read CODE
let drawCircle x y radius =
radius |> circle
|> filled (rgb 150 170 150)
|> alpha 0.5
|> move (x, y)
2.top-to-bottom
1.left-to-right
see also http://bit.ly/1KN8cd0

let drawCircle x y radius =
circle radius
|> filled (rgb 150 170 150)
|> alpha 0.5
|> move (x, y)
see also http://bit.ly/1KN8cd0

let drawCircle x y radius =
circle radius
|> filled (rgb 150 170 150)
|> alpha 0.5
|> move (x, y)
see also http://bit.ly/1KN8cd0

let drawCircle x y radius =
circle radius
|> filled (rgb 150 170 150)
|> alpha 0.5
|> move (x, y)
see also http://bit.ly/1KN8cd0

NASA orbiter crashed
because one engineer
accidentally used miles
instead of kilometres

you’re never too smart
to make mistakes

unit-of-measure

[<Measure>]!
type Pence
e.g.! 42<Pence>!
! 153<Pence>!
! …

10<Meter> / 2<Second> ! = 5<Meter/Second>!
10<Meter> * 2<Second> ! = 20<Meter Second> !
10<Meter> + 10<Meter> ! = 20<Meter>!
10<Meter> * 10! ! ! = 100<Meter>!
10<Meter> * 10<Meter> ! = 100<Meter2>!
10<Meter> + 2<Second> ! // error!
10<Meter> + 2 ! ! ! // error

10<Meter> / 2<Second> ! = 5<Meter/Second>!
10<Meter> * 2<Second> ! = 20<Meter Second> !
10<Meter> + 10<Meter> ! = 20<Meter>!
10<Meter> * 10! ! ! = 100<Meter>!
10<Meter> * 10<Meter> ! = 100<Meter2>!
10<Meter> + 2<Second> ! // error!
10<Meter> + 2 ! ! ! // error

F#
ClojureErlang
Go
RustElm Idris
!?

Duck Typing
If it looks like a duck
and quacks like a
duck, it's a duck

def say_quack(duck):
duck.quack()

def say_quack(duck):
duck.quack()

class Duck:
def quack(self):
print("quack quack!”)

class Duck:
def quack(self):
print("quack quack!”)
!
duck = Duck()
say_quack(duck)
!
> quack quack!

class Bird:
def quack(self):
print(“tweet tweet!”)

class Bird:
def quack(self):
print(“tweet tweet!”)
!
bird = Bird()
say_quack(bird)
!
> tweet tweet!

Convenience
Safety

what if…

Convenience Safety
see also http://bit.ly/1H2fN9i

implicit
interface!
implementation

type Duck interface
{
Quack()
}
see also http://bit.ly/1ER5zVs

func sayQuack(duck Duck) {
duck.Quack()
}
see also http://bit.ly/1ER5zVs

type Donald struct { }
func (d Donald) Quack()
{
fmt.Println(“quack quack!”)
}
see also http://bit.ly/1ER5zVs

type Bird struct { }
func (b Bird) Quack()
{
fmt.Println(“tweet tweet!”)
}
see also http://bit.ly/1ER5zVs

func main() {
donald := Donald{}
sayQuack(donald)
bird := Bird{}
sayQuack(bird)
}
see also http://bit.ly/1ER5zVs

quack quack!
func main() {
donald := Donald{}
sayQuack(donald)
bird := Bird{}
sayQuack(bird)
}

tweet tweet!
func main() {
donald := Donald{}
sayQuack(donald)
bird := Bird{}
sayQuack(bird)
}

type Dog struct { }
func (d Dog) Bark()
{
fmt.Println(“woof woof!”)
}
see also http://bit.ly/1ER5zVs

func main() {
dog := Dog{}
sayQuack(dog)
}
main.go:40: cannot use dog (type Dog) as type
Duck in argument to sayQuack:!
! Dog does not implement Duck (missing
Quack method)
see also http://bit.ly/1ER5zVs

patterns are observed
after the fact
see also http://bit.ly/1ER5zVs

system building is also
a process of learning
and discovery
see also http://bit.ly/1ER5zVs

implementation
package
interface package
see also http://bit.ly/1ER5zVs

encourages precise
interface definitions
see also http://bit.ly/1ER5zVs

F#
ClojureErlang
Go
RustElm Idris
!?

Homoiconicity
…homoiconicity is a property of some
programming languages in which the program
structure is similar to its syntax, and therefore
the program’s internal representation can be
inferred by reading the text’s layout…

code is data
data is code

(let [x 1]
(inc x))
see also http://bit.ly/1PpIrjS

(let [x 1]
(inc x))
!
=> 2
see also http://bit.ly/1PpIrjS

list (1 2 3)
vector [1 2 3]
see also http://bit.ly/1PpIrjS

(let [x 1]
(inc x))
!
list
see also http://bit.ly/1PpIrjS

(let [x 1]
(inc x))
!
symbol
see also http://bit.ly/1PpIrjS

(let [x 1]
(inc x))
!
vector
see also http://bit.ly/1PpIrjS

(let [x 1]
(inc x))
!
list
see also http://bit.ly/1PpIrjS

form :
code as data structure
see also http://bit.ly/1PpIrjS

code data
quote
eval
see also http://bit.ly/1PpIrjS

quote
(+ 1 2)
=> 3
see also http://bit.ly/1PpIrjS

quote
(+ 1 2)
=> 3
(quote (+ 1 2))
=> (+ 1 2)
see also http://bit.ly/1PpIrjS

quote
(+ 1 2)
=> 3
(quote (+ 1 2))
=> (+ 1 2)
‘(+ 1 2)
=> (+ 1 2)
see also http://bit.ly/1PpIrjS

eval
‘(+ 1 2)
=> (+ 1 2)
(eval ‘(+ 1 2))
=> 3
see also http://bit.ly/1PpIrjS

macros

(defmacro assert-equals [actual expected]
‘(let [actual-val# ~actual]
(when-not (= actual-val# ~expected)
(throw
(AssertionError.
(str “FAIL in “ ‘~actual
“n expected: “ ‘~expected
“n actual: “ actual-val#))))))
see also http://bit.ly/1PpIrjS

(assert-equals (inc 1) 2) ; => nil
(assert-equals (inc 1) (+ 0 1))
; => AssertionError FAIL in (inc 1)
; expected: (+ 0 1)
; actual: 2
see also http://bit.ly/1PpIrjS

(assert-equals (inc 1) 2) ; => nil
(assert-equals (inc 1) (+ 0 1))
; => AssertionError FAIL in (inc 1)
; expected: (+ 0 1)
; actual: 2
see also http://bit.ly/1PpIrjS

(assert-equals (inc 1) 2) ; => nil
(assert-equals (inc 1) (+ 0 1))
; => AssertionError FAIL in (inc 1)
; expected: (+ 0 1)
; actual: 2
see also http://bit.ly/1PpIrjS
huh?? where? what? how?

(defmacro assert-equals [actual expected]
‘(let [actual-val# ~actual]
(when-not (= actual-val# ~expected)
(throw
(AssertionError.
(str “FAIL in “ ‘~actual
“n expected: “ ‘~expected
“n actual: “ actual-val#))))))
(assert-equals (inc 1) (+ 0 1))
see also http://bit.ly/1PpIrjS

(defmacro assert-equals [actual expected]
‘(let [actual-val# ~actual]
(when-not (= actual-val# ~expected)
(throw
(AssertionError.
(str “FAIL in “ ‘~actual
“n expected: “ ‘~expected
“n actual: “ actual-val#))))))
(assert-equals (inc 1) (+ 0 1))
see also http://bit.ly/1PpIrjS

(defmacro assert-equals [actual expected]
‘(let [actual-val# ~actual]
(when-not (= actual-val# ~expected)
(throw
(AssertionError.
(str “FAIL in “ ‘~actual
“n expected: “ ‘~expected
“n actual: “ actual-val#))))))
(assert-equals (inc 1) (+ 0 1))
see also http://bit.ly/1PpIrjS

see also http://bit.ly/1PpIrjS
(defmacro assert-equals [actual expected]
‘(let [actual-val# ~actual]
(when-not (= actual-val# ~expected)
(throw
(AssertionError.
(str “FAIL in “ ‘~actual
“n expected: “ ‘~expected
“n actual: “ actual-val#))))))

see also http://bit.ly/1PpIrjS
(defmacro assert-equals [actual expected]
‘(let [actual-val# ~actual]
(when-not (= actual-val# ~expected)
(throw
(AssertionError.
(str “FAIL in “ ‘~actual
“n expected: “ ‘~expected
“n actual: “ actual-val#))))))
‘(

expanded at
compile time
see also http://bit.ly/1PpIrjS

see also http://bit.ly/1PpIrjS
(macroexpand '(assert-equals (inc 1) (+ 0 1)))
; =>
; (let* [actual-value__16087__auto__ (inc 1)]
; (clojure.core/when-not
; (clojure.core/= actual-value__16087__auto__ (+ 0 1))
; (throw (java.lang.AssertionError.
; (clojure.core/str
; "FAIL in " (quote (inc 1))
; "nexpected: " (quote (+ 0 1))
; "n actual: " actual-value__16087__auto__)))))

F#
ClojureErlang
Go
RustElm Idris

GC is great

runtime cost

ownership
see also http://bit.ly/1F6WBVD

memory safety
without GC
see also http://bit.ly/1F6WBVD

ZERO
runtime cost
see also http://bit.ly/1F6WBVD

safety + speed
see also http://bit.ly/1F6WBVD

fn foo() {
// v has ownership of the vector
let v = vec![1, 2, 3];
// mutable binding
let mut v2 = vec![];
}
// vector is deallocated at the
// end of scope,
// this happens deterministically
see also http://bit.ly/1F6WBVD

immutable by default
see also http://bit.ly/1F6WBVD

// take ownership
let v = vec![1, 2, 3];
see also http://bit.ly/1F6WBVD

// take ownership
let v = vec![1, 2, 3];
!
// moved ownership to v2
let v2 = v;
see also http://bit.ly/1F6WBVD

// take ownership
let v = vec![1, 2, 3];
!
// moved ownership to v2
let v2 = v;
!
println!("v[0] is {}", v[0]);
// error: use of moved value: `v`
// println!("v[0] is {}", v[0]);
// ^
see also http://bit.ly/1F6WBVD

fn take(v : Vec<i32>) {
// ownership of vector transferred
// to v in this scope
}
see also http://bit.ly/1F6WBVD

// take ownership
let v = vec![1, 2, 3];
!
// moved ownership
take(v);
see also http://bit.ly/1F6WBVD

// take ownership
let v = vec![1, 2, 3];
!
// moved ownership
take(v);
!
println!("v[0] is {}", v[0]);
// error: use of moved value: `v`
// println!("v[0] is {}", v[0]);
// ^
see also http://bit.ly/1F6WBVD

see also http://bit.ly/1F6WBVD

see also http://bit.ly/1F6WBVD
let me buy
your book

see also http://bit.ly/1F6WBVD
sure thing!

see also http://bit.ly/1F6WBVD
thanks

see also http://bit.ly/1F6WBVD
BURN!!! !
>:D

see also http://bit.ly/1F6WBVD
but I
still need it..!
:’(

borrowing
see also http://bit.ly/1F6WBVD

// note we're taking a reference,
// &Vec<i32>, instead of Vec<i32>
fn take(v : &Vec<i32>) {
// no need to deallocate the vector
// after we go out of scope here
}
see also http://bit.ly/1F6WBVD

// take ownership
let v = vec![1, 2, 3];
!
// notice we're passing a reference,
// &v, instead of v
take(&v); // borrow ownership
!
println!("v[0] is {}", v[0]);
// v[0] is 1
see also http://bit.ly/1F6WBVD

see also http://bit.ly/1F6WBVD
let me
borrow your
book

see also http://bit.ly/1F6WBVD
sure thing!

see also http://bit.ly/1F6WBVD
thanks

see also http://bit.ly/1F6WBVD
I’m done,
here you go

see also http://bit.ly/1F6WBVD
thanks

see also http://bit.ly/1F6WBVD
immutable by default

fn take(v : &Vec<i32>) {
v.push(5);
}
!
let v = vec![];
take(&v);
// cannot borrow immutable borrowed
// content `*v` as mutable
// v.push(5);
// ^
see also http://bit.ly/1F6WBVD

fn take(v : &mut Vec<i32>) {
v.push(5);
}
!
let mut v = vec![];
take(&mut v);
!
println!("v[0] is {}", v[0]);
// v[0] is 5
see also http://bit.ly/1F6WBVD

borrowing
rules
see also http://bit.ly/1F6WBVD

see also http://bit.ly/1F6WBVD
Rule 1.!
!
the borrower’s scope must not
outlast the owner

see also http://bit.ly/1F6WBVD
Rule 2.!
!
one of the following, but not both:!
2.1 0 or more refs to a resource!
2.2 exactly 1 mutable ref

see also http://bit.ly/1F6WBVD
data race
There is a ‘data race’ when two or more pointers
access the same memory location at the same
time, where at least one of them is writing, and
the operations are not synchronised.

see also http://bit.ly/1F6WBVD
data race
a. two or more pointers to the same resource!
b. at least one is writing!
c. operations are not synchronised

see also http://bit.ly/1F6WBVD
Data Race Conditions!
a. two or more pointers to the same resource!
b. at least one is writing!
c. operations are not synchronised
Borrowing Rules!
one of the following, but not both:!
! 2.1 0 or more refs to a resource!
! 2.2 exactly 1 mutable ref

see also http://bit.ly/1F6WBVD
Data Race Conditions!
a. two or more pointers to the same resource!
b. at least one is writing!
c. operations are not synchronised
Borrowing Rules!
one of the following, but not both:!
! 2.1 0 or more refs to a resource!
! 2.2 exactly 1 mutable ref

see also http://bit.ly/1F6WBVD

F#
ClojureErlang
Go
RustElm Idris
!!!

seen generics?
aka parametric polymorphism

List<T>

List<T>
List<int> List<Cat>
List<string>

what if…

types that depend on
arbitrary values?

Vect n a
vector of n elements of type a

zipWith :
(a -> b -> c)
-> Vect n a
-> Vect n b
-> Vect n c

zipWith f [] [] = []
zipWith f (x :: xs) (y :: ys) =
f x y :: zipWith f xs ys

Type Driven Development

making invalid state
UNREPRESENTABLE

see also https://vimeo.com/123606435

F#
ClojureErlang
Go
RustElm Idris

Functional Reactive
Programming

Value over Time

Time
Value

Signals

Move Up
Move Down

private var arrowKeyUp:Bool;
private var arrowKeyDown:Bool;
!
private var platform1:Platform;
private var platform2:Platform;
private var ball:Ball;

function keyDown(event:KeyboardEvent):Void
{
if (currentGameState == Paused &&
event.keyCode == 32) {
setGameState(Playing);
} else if (event.keyCode == 38) {
! ! arrowKeyUp = true;!
}else if (event.keyCode == 40) {
! ! arrowKeyDown = true;!
}
}

function keyUp(event:KeyboardEvent):Void {
if (event.keyCode == 38) {
! ! arrowKeyUp = false;!
} else if (event.keyCode == 40) {
! ! arrowKeyDown = false;!
}
}

function everyFrame(event:Event):Void {
if(currentGameState == Playing){
if (arrowKeyUp) {
platform1.y -= platformSpeed;
}
if (arrowKeyDown) {
platform1.y += platformSpeed;
}
if (platform1.y < 5)
platform1.y = 5;
if (platform1.y > 395)
platform1.y = 395;
}
}

function everyFrame(event:Event):Void {
if(currentGameState == Playing){
if (arrowKeyUp) {
platform1.y -= platformSpeed;
}
if (arrowKeyDown) {
platform1.y += platformSpeed;
}
if (platform1.y < 5) !
! ! ! platform1.y = 5;!
! ! if (platform1.y > 395) !
! ! ! platform1.y = 395;!
}
}

source files
state changes

source files execution

source files execution

mental model
input state new state behaviour
{ x; y } { x; y-speed }
{ x; y } { x; y+speed }
timer { x; y } { x; y } draw platform
… … … …

transformation
let y = f(x)
Imperative Functional
x.f()
mutation

transformations
simplify problem
decomposition

Move Up
Move Down

type alias Platform = {x:Int, y:Int}
defaultPlatform = {x=5, y=0}
!
delta = Time.fps 20
input = Signal.sampleOn delta Keyboard.arrows
!
cap x = max 5 <| min x 395
!
p1 : Signal Platform
p1 = foldp ({x, y} s -> {s | y <- cap <| s.y + 5*y})
defaultPlatform
input

type alias Platform = {x:Int, y:Int}!
defaultPlatform = {x=5, y=0}
!
delta = Time.fps 20
input = Signal.sampleOn delta Keyboard.arrows
!
cap x = max 5 <| min x 395
!
p1 : Signal Platform
p1 = foldp ({x, y} s -> {s | y <- cap <| s.y + 5*y})
defaultPlatform
input

type alias Platform = {x:Int, y:Int}
defaultPlatform = {x=5, y=0}
!
delta = Time.fps 20
input = Signal.sampleOn delta Keyboard.arrows
!
cap x = max 5 <| min x 395
!
p1 : Signal Platform
p1 = foldp ({x, y} s -> {s | y <- cap <| s.y + 5*y})
defaultPlatform
input

Keyboard.arrows
UP { x=0, y=1 }
DOWN { x=0, y=-1 }
LEFT { x=-1, y=0 }
RIGHT { x=1, y=0 }

type alias Platform = {x:Int, y:Int}
defaultPlatform = {x=5, y=0}
!
delta = Time.fps 20
input = Signal.sampleOn delta Keyboard.arrows
!
cap x = max 5 <| min x 395
!
p1 : Signal Platform!
p1 = foldp ({x, y} s -> {s | y <- cap <| s.y + 5*y})
defaultPlatform
input

type alias Platform = {x:Int, y:Int}
defaultPlatform = {x=5, y=0}
!
delta = Time.fps 20
input = Signal.sampleOn delta Keyboard.arrows
!
cap x = max 5 <| min x 395
!
p1 : Signal Platform
p1 = foldp ({x, y} s -> {s | y <- cap <| s.y + 5*y})
defaultPlatform
input

type alias Platform = {x:Int, y:Int}
defaultPlatform = {x=5, y=0}
!
delta = Time.fps 20
input = Signal.sampleOn delta Keyboard.arrows
!
cap x = max 5 <| min x 395
!
p1 : Signal Platform
p1 = foldp ({x, y} s -> {s | y <- cap <| s.y + 5*y})
defaultPlatform
input

type alias Platform = {x:Int, y:Int}
defaultPlatform = {x=5, y=0}
!
delta = Time.fps 20
input = Signal.sampleOn delta Keyboard.arrows
!
cap x = max 5 <| min x 395
!
p1 : Signal Platform
p1 = foldp ({x, y} s -> {s | y <- cap <| s.y + 5*y})
defaultPlatform
input

see also http://oreil.ly/1i5CyhO

“I thought of objects being like
biological cells and/or
individual computers on a
network, only able to
communicate with messages.”
- Alan Kay

“OOP to me means only
messaging, local retention and
protection and hiding of state-
process, and extreme late-
binding of all things.”
- Alan Kay

F#
ClojureErlang
Go
RustElm Idris
!?

actor model

actor
state
mailbox

actors share nothing

actor
state
mailbox
actor

actor
state
mailbox
actor

processing!
storage!
communication

loop (Map) ->!
receive!
{get, Key, Pid} ->!
Pid ! maps:get(Key, Map, not_found),!
loop(Map);!
{set, Key, Value} ->!
loop(maps:put(Key, Value, Map))!
end.

loop (Map) ->!
receive!
{get, Key, Pid} ->!
Pid ! maps:get(Key, Map, not_found),!
loop(Map);!
{set, Key, Value} ->!
loop(maps:put(Key, Value, Map))!
end.

loop (Map) ->!
receive!
{get, Key, Pid} ->!
Pid ! maps:get(Key, Map, not_found),!
loop(Map);!
{set, Key, Value} ->!
loop(maps:put(Key, Value, Map))!
end.

loop (Map) ->!
receive!
{get, Key, Pid} ->!
Pid ! maps:get(Key, Map, not_found),!
loop(Map);!
{set, Key, Value} ->!
loop(maps:put(Key, Value, Map))!
end.

client (N, Pid) ->!
Pid ! {set, N, N},!
Pid ! {get, N, self()},!
receive!
not_found -> io:format(“~p :-(~n”, [N]);!
N -> io:format(“~p :-)~n”, [N]);!
_ -> io:format(“~p …~n”, [N])!
end.

client (N, Pid) ->!
Pid ! {set, N, N},!
Pid ! {get, N, self()},!
receive!
not_found -> io:format(“~p :-(~n”, [N]);!
N -> io:format(“~p :-)~n”, [N]);!
_ -> io:format(“~p …~n”, [N])!
end.

client (N, Pid) ->!
Pid ! {set, N, N},!
Pid ! {get, N, self()},!
receive!
not_found -> io:format(“~p :-(~n”, [N]);!
N -> io:format(“~p :-)~n”, [N]);!
_ -> io:format(“~p …~n”, [N])!
end.

start(N) ->!
Kvs = spawn(mod, loop, [#{}]),!
[spawn(mod, client, [X, Kvs]) !
|| X <- lists:seq(1,N)].

actors are cheap

no locks!

need state?!
talk to the actor!

location
transparency

makes you !
THINK !
about !
distributed systems

messaging promotes
failure thinking

Distributed
Computing

Network is reliable!
Latency is zero!
Bandwidth is infinite!
Network is secure!
Topology doesn't change!
There is one administrator!
Transport cost is zero!
The network is homogeneous
8 fallacies of distributed computing

supervise & restart

F#
ClojureErlang
Go
RustElm Idris

10,000 hours to be
good at something
see also http://bit.ly/1KN7SLq

10,000 hours to be
good at something
see also http://bit.ly/1KN7SLq

10,000 hours to reach
top of an ultra-
competitive field
see also http://bit.ly/1KN7SLq

the first 20 hours -
how to learn anything
see also http://bit.ly/1KN7SLq

Practice Time
Howgoodyouare
see also http://bit.ly/1KN7SLq

1.Deconstruct the skill
see also http://bit.ly/1KN7SLq

1.Deconstruct the skill!
2.Learn enough to self-correct
see also http://bit.ly/1KN7SLq

1.Deconstruct the skill!
2.Learn enough to self-correct!
3.Remove practice barriers
see also http://bit.ly/1KN7SLq

1.Deconstruct the skill!
2.Learn enough to self-correct!
3.Remove practice barriers!
4.Practice at least 20 hrs
see also http://bit.ly/1KN7SLq

learn a new paradigm!
not a new syntax
see also http://bit.ly/1IzXVSo

logic programming

stack-oriented
programming

array programming

“A language that doesn't
affect the way you think
about programming, is not
worth knowing.”
- Alan Perlis

see also http://bit.ly/1IzXVSo

see also http://bit.ly/1IzXVSo

“Learning is an act of creation
itself, because something
happens in you that wasn't
there before.”
- Alan Kay

@theburningmonk
theburningmonk.com
github.com/theburningmonk