@alpacalang

Static Typing on the BEAM

@alpacalang

Who am I?

j14159

Director of Platform Engineering

@alpacalang

What Is Alpaca?• Statically Typed

• Functional

• http://alpaca-lang.org

@alpacalang

What Is Alpaca?• Type inference (Hindley-Milner)

• ML-family inspired

• Trying to stay simple and obvious

• Started January 2016, open-sourced June

@alpacalang

It is not…• Standard ML

• OCaml

• Haskell

@alpacalang

Doesn’t care about…• Higher kinded types

• Dependent typing

• Effect typing

• Ad-hoc polymorphism (e.g. typeclasses)

@alpacalang

A masochist’s guideto learning

Damas-Hindley-Milner

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Why (build it)?

@alpacalang

❤ Erlang

❤ Static Typing

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Types and patterns

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Types and patterns

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Uh-oh…

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Testing

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Stealing from Erlang❤ Erlang

❤ Pattern matching

❤ Tests

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Static typing

CC0

Chri

stop

h Br

aun

@alpacalang

Tests and Types

CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=10407097

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Algebraic Data Types (ADTs)

❤ pattern matching

tests

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Actual Alpaca

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Actual Alpaca

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What’s important?

@alpacalang

Safety

CC0

Chri

stop

h Br

aun

@alpacalang

Utility

Copy

righ

t St

eve

Bran

am, cl

oseg

rain

.com

@alpacalang

Simplicity

CC-B

Y-SA

3.0

Jan

ekpf

eife

r

@alpacalang

@alpacalang

Why…?• Target BEAM?

• Borrow from ML?

@alpacalang

Why BEAM?• VM

• Core Erlang

@alpacalang

Why ML?

Brevity

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Unification

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And a few similarities

Some Differences

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Some differences

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Maps

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Maps

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ADTs

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ADTs

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ADTs

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ADTs

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Don’t like it. Not one bit.

Any

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We hates it

@alpacalang

Matching

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Matching

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Type tests

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Type tests

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Clauses

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Clauses

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Clauses

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Clauses

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FFI

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FFI

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FFI

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My favourites• typed messages

• records with row polymorphism

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Typed Messages

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Erlang

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Alpaca

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receiver 'message_type 'return_type

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receiver 'message_type 'return_type

pid 'message_type

@alpacalang

Receivers

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Receivers

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Receivers

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Receivers

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Receivers

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Receivers

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unify(int, receiver atom int)

receiver atom int

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Receivers

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Receivers

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unify(A, receiver B C)

receiver B A

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Spawning

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pid ‘a

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Spawning

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No receiver?

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Row polymorphism!

Records

@alpacalang

Row polymorphism

@alpacalang

Row polymorphism

@alpacalang

Row polymorphism

@alpacalang

Row polymorphism

@alpacalang

Row polymorphism

@alpacalang

Transformations

@alpacalang

Transformations

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Trade-offs

@alpacalang

Processes

CC-B

Y-SA

4.0

Seo

ul M

etro

poli

tan

Fire

& D

isas

ter

Head

quar

ters

@alpacalang

Code Reloading

CC-B

Y 2.

0 Ro

bert

Fre

iber

ger

@alpacalang

OTP Interop?

CC-B

Y-SA

3.0

Mag

nus

Mans

ke

@alpacalang

Compiler StructureFront End

AST Generation

Back End

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Compiler Back EndTyper

Match Exhaustiveness

Code Generation

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Compiler Back Endmodule_name.alp

alpaca_module_name.beam

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Code of Conduct v1.4

Contributor Covenant

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Contributors

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Accessibility

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Growth

CC-B

Y-SA

3.0

Dor

otan

m

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Communicating• https://github.com/alpaca-lang

• #alpaca-lang on freenode.net

• Google Group https://groups.google.com/forum/#!forum/alpaca-lang

@alpacalang

Where to help?

CC-B

Y-SA

3.0

Myk

ola

Swar

nyk

@alpacalang

Community Projects• rebar3 plugin

• Alpaca shell

• emacs mode

• VSCode extension

@alpacalang

Where to help?• standard library

• tooling (editors, etc)

• module system ideas

@alpacalang

Where to help?• Alpaca examples

• libraries using the FFI

• documentation

• participate in feature discussions

• use it and break it! We like finding bugs!

@alpacalang

Where to help?

CC-B

Y-SA

3.0

Myk

ola

Swar

nyk

@alpacalang

More details?• Language tour:https://github.com/alpaca-lang/alpaca/blob/master/Tour.md

• Where the typer started:http://okmij.org/ftp/ML/generalization.html

• Row polymorphism:https://www.cs.cmu.edu/~neelk/rows.pdf