on Steroids Freestyle Free & Tagless Separation of Concerns...Practical Problems with Free #1 Boilerplate @miciek Freestyle which is built on top of Cats @miciek After Freestyle No

@miciek

Michał Płachta

Freestyle Free & Tagless

www.michalplachta.comwww.michalplachta.com

Separation of Concerns on Steroids

@miciek

@miciek

Separation of Concerns… not

@miciek

Intelligent Thinking

It is, that one is willing to study in depth an aspect of one's subject matter in isolation for the sake of its own consistency, all the time knowing that one is occupying oneself only with one of the aspects.

Portrait by Hamilton Richards - manuscripts of Edsger W. Dijkstra, University Texas at Austin, CC BY-SA 3.0,

https://commons.wikimedia.org/w/index.php?curid=4204157

“

@miciek

Separate All the Things!

High LevelLogic

Business #1 Business #2

Logging

Metrics

DB Access

Low Level Logic

High LevelLogic

Low Level Logic

business concern

technical concern

@miciek

Separate All the Things!

High LevelLogic


Logging

Metrics

DB Access

Low Level Logic

High LevelLogic

Low Level Logic

business concern

technical concern

knows about

@miciek

No outgoing arrows = separated

High LevelLogic


Logging

Metrics

DB Access

Low Level Logic

High LevelLogic

Low Level Logic

@miciek

Developer Experience

Intended Design

Real Life Usage

https://i.imgur.com/JIXACph.jpg


@miciek


Database

https://i.imgur.com/JIXACph.jpg

Business #1

High LevelLogic

Low Level Logic

DB Access

@miciek


https://cdn-images-1.medium.com/max/1920/1*WeZlYd1Exr2JVup0MeSwaw.jpeg

@miciek

We’ll use Free

Free[F, A]A program that uses

language F to produce A

@miciek

Journey

Prisoner’s Dilemma

3 apps15 overlapping concernsusing Cats & Freestyle

more Freestyle Tagless Final

hardcore concern separation

@miciek


Simple example with non-trivial mechanics...

@miciek


@miciek


The other prisoner is GUILTY!

I prefer to remainSILENT

or

@miciek


GUILTY!

GUILTY!

3 years

3 years

@miciek


GUILTY!

GUILTY!

3 years

3 years

...

...

1 year

1 year

@miciek


GUILTY!

GUILTY!

3 years

3 years

...

...

1 year

1 year

GUILTY!

...

FREE

3 years

@miciek


GUILTY!

GUILTY!

3 years

3 years

...

...

1 year

1 year

GUILTY!

...

FREE

3 years

...

GUILTY!

3 years

FREE

@miciek

Repeated Prisoner’s Dilemmahttp://ncase.me/trust/

@miciek

Journey




@miciek

Hot Seat GameWelcome to Hot Seat Game, Prisoner A!What's your name?> AdamHello, Adam!Welcome to Hot Seat Game, Prisoner B!What's your name?> JaneHello, Jane!

@miciek

Hot Seat GameWelcome to Hot Seat Game, Prisoner A!What's your name?> AdamHello, Adam!Welcome to Hot Seat Game, Prisoner B!What's your name?> JaneHello, Jane!Adam, is Jane guilty?> nYour decision: SilenceJane, is Adam guilty?> nYour decision: SilenceVerdict for Adam is 1 yearVerdict for Jane is 1 year

@miciek

Hot Seat Game

@miciek

Hot Seat Game Concerns

Hot SeatLogic

business concern

technical concern

knows about

@miciek


Hot SeatLogicComputing

VerdictPlayer

Interaction

Player Communicationusing Console

business concern

technical concern

knows about

@miciek



VerdictPlayer

Interaction


@miciek



VerdictPlayer

Interaction


Free[F, A]

@miciek

ComputingVerdictConcern #1

@miciek

Player InteractionConcern #2

Operation name Return value

@miciek

Player InteractionConcern #2

@miciek

Hot Seat LogicConcern #3

@miciek

Player Interaction using ConsoleConcern #4

How to transform Player[A] into IO[A]?

@miciek

Player Interaction using ConsoleConcern #4

@miciek

Connecting the Dots


VerdictPlayer

Interaction


pure function Free[Player, A]

Player[A] ~> IO[A]

Free[S, Unit]

@miciek

End of the World

@miciek

Practical Problems with Free#1 Boilerplate

@miciek

Freestyle

which is built on top of Cats

@miciek

After FreestyleNo Boilerplate Algebra

@miciek

After FreestyleNo Boilerplate Interpreter

@miciek

Playing with a Bot

Adding new features is adding more concerns!

@miciek

Playing with a Bot

Welcome to Single Player Game!What's your name?> MichalHello, Michal!Michal, is WALL-E guilty?> nYour decision: SilenceVerdict for Michal is 1 year

Adding new features is adding more concerns!

@miciek

Reusing Values

ComputingVerdict

Player Interaction


Unknown OpponentLogic

Opponent Interaction

#1 #2

#3Bot

Opponent

@miciek


Freestyle generates all the case classes and other helpers!

@miciek

Unknown Opponent Logic

@miciek

Friend’s Reaction

@miciek

End of the World

@miciek

End of the World

???

@miciek

Bot Opponent

@miciek

End of the World

@miciek

Workflow

1. Define operations2. Create programs3. Try to run them4. Fix errors by implementing interpreters

Player Interaction

Unknown Opponent

Unknown Opponent

@miciek

Different Interpreter for Opponent?

ComputingVerdict

Player Interaction




? Bot Opponent

@miciek

Remote Opponent

ComputingVerdict

Player Interaction




Remote Opponent

Bot Opponent

@miciek

Meeting Remote Opponent

Player A Player B

RegisterAsWaiting

GetWaitingPlayers

JoinWaitingPlayer

CheckIfOpponentJoined

UnregisterWaiting

foundPlayer A

foundPlayer B

@miciek

Matchmaking

@miciek

Matchmaking Programs

Player A Player B

waitForOpponent findOpponent

RegisterAsWaiting

GetWaitingPlayers

JoinWaitingPlayer

CheckIfOpponentJoined

UnregisterWaiting

@miciek

Find Opponent

@miciek

Remote Opponent

ComputingVerdict

Player Interaction




Remote Opponent

Bot Opponent

@miciek

Bot OpponentRecap:

@miciek

Remote Opponent

What should we interpret Opponent into?

???

@miciek

Remote Opponent

We should interpret Opponent into Free

@miciek

Workflow

1. Define operations2. Create programs3. Try to run them4. Fix errors by implementing interpreters

Player Interaction

Unknown Opponent

Unknown Opponent

@miciek

Recap: Game with a Bot



Bot Opponent

var state: Map...

@miciek

Interpreting into Free



Bot Opponent

var state: Map...

Remote Opponent is interpreting into

another Free program!

Remote Opponent

@miciek

Multiplayer Game Mode


Remote Opponent

Matchmaking

?

Let’s zoom in!

@miciek

Multiplayer Game Mode


Remote Opponent

Matchmaking

Remote Actor Matchmaker

@miciek

MatchmakingRecap:

@miciek

Matchmaking Server Handler

@miciek

End of the World

@miciek

3 Game Modes = 15 Concerns + 31 Tests

ComputingVerdict

Player Interaction




Remote Opponent

Bot Opponent

Decision Registry

Matchmaking

Matchmaking Server

Decision Server Timing

Hot SeatLogic

EoW

Thread Timing

x3

Player Local Interaction

@miciek

3 Game Modes = 15 Concerns + 31 Tests

ComputingVerdict

Player Interaction




Remote Opponent

Bot Opponent

Decision Registry

Matchmaking

Matchmaking Server

Decision Server Timing

Hot SeatLogic

EoW

Thread Timing

x3

Player Local Interaction

Thread.sleep

printlnvar

@miciek

Journey




@miciek

FreestyleComposing Algebras using Modules

@miciek

Pure CatsComposing Algebras using Coproducts

@miciek

Pure Cats FreeCreating Lots of Objects

@miciek

Journey




@miciek

Final TaglessInstead of wrapping everything in Free

@miciek

Final TaglessLet’s execute instructions directly!

F can be anything!

@miciek

Final Tagless using Freestyle

@miciek

Course of Action

▪ Use Free directly using cats or scalaz▪ Use Final Tagless directly▪ When comfortable, start using freestyle▪ Decide @tagless or @free per use case

@miciek

@free or @tagless?

@free @taglessprogram is data program is an expression

plain values expressions parametrized by F[_]

stack-safe stack-safe iff F[_] is stack-safe

Remember: Mix and match your algebras using Freestyle!

More here:https://softwaremill.com/free-tagless-compared-how-not-to-commit-to-monad-too-early/

Note that Freestyle gets rid of some problems mentioned there!

https://softwaremill.com/free-tagless-compared-how-not-to-commit-to-monad-too-early/

@miciek

Learn More

https://github.com/miciek/free-prisoners6 apps / 3 in Free / 3 in Freestyle / 2 Akka actors / 31 tests

https://github.com/miciek/free-prisoners

@miciek

Michał Płachta

www.michalplachta.com

THANKS!

Freestyle Free & Tagless

https://github.com/miciek/free-prisoners6 pure apps / 15 concerns / 2 Akka actors / 31 tests

@miciek
https://github.com/miciek/free-prisoners

Documents

on Steroids Freestyle Free & Tagless Separation of Concerns...Practical Problems with Free #1 Boilerplate @miciek Freestyle which is built on top of Cats @miciek After Freestyle No