THE UNREASONABLE EFFECTIVENESS OF MONADS 🔥 🚀 A U T O M A T I O N , S T R U C T U R E , & P U R E LY F U N C T I O N A L E F F E C T S ⚙ ✨
A presentation at Øredev 2019 in November 2019 in Malmö, Sweden by Brooklyn Zelenka
THE UNREASONABLE EFFECTIVENESS OF MONADS 🔥 🚀 A U T O M A T I O N , S T R U C T U R E , & P U R E LY F U N C T I O N A L E F F E C T S ⚙ ✨
Simplicity is prerequisite for reliability 🔑 EDSGER DIJKSTRA
THE UNREASONABLE EFFECTIVENESS OF MONADS B R O O K LY N Z E L E N K A , @ e x p e d e
THE UNREASONABLE EFFECTIVENESS OF MONADS B R O O K LY N Z E L E N K A , @ e x p e d e • Cofounder/CTO at Fission • https://fission.codes • PLT & VM enthusiast • Previously an Ethereum Core Dev • Primary author of Witchcraft Suite • Used to teach Elixir professionally • Now with a Haskell team 😉
THE UNREASONABLE EFFECTIVENESS OF MONADS S A L E S P I TC H
THE UNREASONABLE EFFECTIVENESS OF MONADS S A L E S P I TC H
250 THE UNREASONABLE EFFECTIVENESS OF MONADS E D U C AT I O N I N V E S T M E N T V S C O M P L E X I T Y Structured Unconstrained
THE UNREASONABLE EFFECTIVENESS OF MONADS E D U C AT I O N I N V E S T M E N T V S C O M P L E X I T Y 1000 750 500 Unconstrained 250 Structured
THE UNREASONABLE EFFECTIVENESS OF MONADS E F F E C T- F O C U S E D
THE UNREASONABLE EFFECTIVENESS OF MONADS E F F E C T- F O C U S E D • Monads are extremely well defined
THE UNREASONABLE EFFECTIVENESS OF MONADS E F F E C T- F O C U S E D • Monads are extremely well defined • Steer away from the math 🚫
THE UNREASONABLE EFFECTIVENESS OF MONADS E F F E C T- F O C U S E D • Monads are extremely well defined • Steer away from the math • Many uses, but the main practical one is effects 🚫
THE UNREASONABLE EFFECTIVENESS OF MONADS TA B L E O F C O N T E N T S
THE UNREASONABLE EFFECTIVENESS OF MONADS TA B L E O F C O N T E N T S • Some seemingly unrelated — but already familiar — concepts • Structured abstraction • Technical prerequisites • The essence of the monadic style • Common examples
STRUCTURED ABSTRACTION
STRUCTURED ABSTRACTION 🧱
STRUCTURED ABSTRACTION structure / ˈstrʌk tʃər / 1. A mode of building, construction, or organization; arrangement of parts, elements, or constituents e.g. a pyramidal structure. 🗼
STRUCTURED ABSTRACTION abstraction / æbˈstræk ʃən / 1. Something that concentrates in itself the essential qualities of anything more extensive or more general, or of several things; its essence. ⚗
STRUCTURED ABSTRACTION TRADE-OFFS • “GOTOs considered harmful” • Exchange control for understanding Libraries Applications
STRUCTURED ABSTRACTION TRADE-OFFS • “GOTOs considered harmful” • Exchange control for understanding Libraries GENERALITY 🌏 ⚖ POWER 🚀 Applications
STRUCTURED ABSTRACTION TRADE-OFFS • “GOTOs considered harmful” • Exchange control for understanding Libraries GENERALITY 🌏 ⚖ POWER 🚀 Applications
STRUCTURED ABSTRACTION TRADE-OFFS • “GOTOs considered harmful” • Exchange control for understanding Functor/Enum Libraries GENERALITY 🌏 ⚖ POWER 🚀 Applications
STRUCTURED ABSTRACTION TRADE-OFFS • “GOTOs considered harmful” • Exchange control for understanding Functor/Enum Libraries GENERALITY 🌏 Persistent/Ecto ⚖ POWER 🚀 Applications
STRUCTURED ABSTRACTION TRADE-OFFS • “GOTOs considered harmful” • Exchange control for understanding Monad 😉 Functor/Enum Libraries GENERALITY 🌏 Persistent/Ecto ⚖ POWER 🚀 Applications
STRUCTURED ABSTRACTION SIMPLE EXAMPLE: SEMIGROUP
STRUCTURED ABSTRACTION SIMPLE EXAMPLE: SEMIGROUP • Not a data structure
STRUCTURED ABSTRACTION SIMPLE EXAMPLE: SEMIGROUP • Not a data structure • Not a function
STRUCTURED ABSTRACTION SIMPLE EXAMPLE: SEMIGROUP • Not a data structure • Not a function • An interface & rules!
STRUCTURED ABSTRACTION SIMPLE EXAMPLE: SEMIGROUP • Not a data structure • Not a function • An interface & rules!
STRUCTURED ABSTRACTION A SEMIGROUP ON…
STRUCTURED ABSTRACTION A SEMIGROUP ON…
STRUCTURED ABSTRACTION A SEMIGROUP ON…
STRUCTURED ABSTRACTION A SEMIGROUP ON…
STRUCTURED ABSTRACTION UNLAWFUL COUNTEREXAMPLE 🚨
STRUCTURED ABSTRACTION W E U S E L O T S O F D I F F E R E N T F E AT U R E S D A I LY
STRUCTURED ABSTRACTION W E U S E L O T S O F D I F F E R E N T F E AT U R E S D A I LY • Promises (AKA async/await) • Network • Database • Long computation
STRUCTURED ABSTRACTION W E U S E L O T S O F D I F F E R E N T F E AT U R E S D A I LY • Promises (AKA async/await) • Network • Database • Long computation • throw/catch
STRUCTURED ABSTRACTION W E U S E L O T S O F D I F F E R E N T F E AT U R E S D A I LY • Promises (AKA async/await) • Network • Database • Long computation • throw/catch • Tracing
STRUCTURED ABSTRACTION W E U S E L O T S O F D I F F E R E N T F E AT U R E S D A I LY • Promises (AKA async/await) • Network • Database • Long computation • throw/catch • Tracing • Context or config values
STRUCTURED ABSTRACTION B U T M AY B E N O T S O D I F F E R E N T
STRUCTURED ABSTRACTION B U T M AY B E N O T S O D I F F E R E N T
STRUCTURED ABSTRACTION B U T M AY B E N O T S O D I F F E R E N T
STRUCTURED ABSTRACTION B U T M AY B E N O T S O D I F F E R E N T
STRUCTURED ABSTRACTION B U T M AY B E N O T S O D I F F E R E N T
STRUCTURED ABSTRACTION B U T M AY B E N O T S O D I F F E R E N T
STRUCTURED ABSTRACTION B U T M AY B E N O T S O D I F F E R E N T
STRUCTURED ABSTRACTION B U T M AY B E N O T S O D I F F E R E N T 🚂 ⏲ ⛓ 🖊
STRUCTURED ABSTRACTION YOU’RE ALREADY DOING THIS
STRUCTURED ABSTRACTION YOU’RE ALREADY DOING THIS 🤾 S U R P R I S E AT T A C K E F F E C T S 💥
FRONT EFFECTS
FRONT EFFECTS 👋
FRONT EFFECTS SIDE EFFECTS
FRONT EFFECTS SIDE EFFECTS • Implicit effects that happen “off to the side”
FRONT EFFECTS SIDE EFFECTS • Implicit effects that happen “off to the side” • Built into the language / platform
FRONT EFFECTS SIDE EFFECTS • Implicit effects that happen “off to the side” • Built into the language / platform • Hard to inspect
FRONT EFFECTS SIDE EFFECTS • Implicit effects that happen “off to the side” • Built into the language / platform • Hard to inspect • …thus hard to change, compose, or test
FRONT EFFECTS E F F E C T S - A S - D ATA
FRONT EFFECTS E F F E C T S - A S - D ATA • Data is simple
FRONT EFFECTS E F F E C T S - A S - D ATA • Data is simple • Effects don’t need to be separate: express effects as data
FRONT EFFECTS E F F E C T S - A S - D ATA • Data is simple • Effects don’t need to be separate: express effects as data • Write your own effects
FRONT EFFECTS E F F E C T S - A S - D ATA • Data is simple • Effects don’t need to be separate: express effects as data • Write your own effects • Inspect them as needed
FRONT EFFECTS E F F E C T S - A S - D ATA • Data is simple • Effects don’t need to be separate: express effects as data • Write your own effects • Inspect them as needed • Compose as needed
FRONT EFFECTS ENTER THE MONAD
FRONT EFFECTS ENTER THE MONAD • A common interface to make this straightforward!
FRONT EFFECTS ENTER THE MONAD • A common interface to make this straightforward! • Learn once, use everywhere
THE FUNCTOR TOWER
THE FUNCTOR TOWER 🗼 LET ’S COVER SOME INTERNALS
THE FUNCTOR TOWER Progress is possible only if we train ourselves to think about programs without thinking of them as pieces of executable code 🚀 EDSGER DIJKSTRA
THE FUNCTOR TOWER F U N CTO R
THE FUNCTOR TOWER F U N CTO R • Always returns the same shape!
THE FUNCTOR TOWER F U N CTO R • Always returns the same shape! Functor.map
THE FUNCTOR TOWER F U N CTO R • Always returns the same shape! Functor.map
THE FUNCTOR TOWER A P P LY Functor.map
THE FUNCTOR TOWER A P P LY Functor.map Apply.apply
THE FUNCTOR TOWER A P P L I C AT I V E Functor.map Apply.apply 🙋 AKA return, pure, of, unit
THE FUNCTOR TOWER A P P L I C AT I V E Functor.map Apply.apply Applicative.wrap 🙋 AKA return, pure, of, unit
THE FUNCTOR TOWER CHAIN Functor.map Apply.apply Applicative.wrap
THE FUNCTOR TOWER CHAIN Functor.map Apply.apply Applicative.wrap Chain.bind
THE FUNCTOR TOWER MONAD 6 Functor.map Apply.apply Applicative.wrap Chain.bind
THE FUNCTOR TOWER MONAD 6 Functor.map Apply.apply Applicative.wrap Chain.bind Monad • Monads are the essence of Turing complete, effectual computation
R E S U LT ( S )
THE FUNCTOR TOWER M O N A D ( F I N A L LY ! )
E I T H E R / R E S U LT
E I T H E R / R E S U LT 🚂 RAILROAD PROGRAMMING
E I T H E R / R E S U LT RAILROAD PROGRAMMING
E I T H E R / R E S U LT RAILROAD PROGRAMMING Happy Path (Continue) Error Case (Skip) No Effect (Afterwards)
E I T H E R / R E S U LT RAILROAD PROGRAMMING Happy Path (Continue) Error Case (Skip) No Effect (Afterwards)
E I T H E R / R E S U LT RAILROAD PROGRAMMING Happy Path (Continue) Error Case (Skip) No Effect (Afterwards)
E I T H E R / R E S U LT RAILROAD PROGRAMMING Happy Path (Continue) Error Case (Skip) No Effect (Afterwards)
E I T H E R / R E S U LT RAILROAD PROGRAMMING Happy Path (Continue) Error Case (Skip) No Effect (Afterwards)
E I T H E R / R E S U LT RAILROAD PROGRAMMING Happy Path (Continue) Error Case (Skip) No Effect (Afterwards)
E I T H E R / R E S U LT RAILROAD PROGRAMMING Happy Path (Continue) Error Case (Skip) No Effect (Afterwards)
E I T H E R / R E S U LT RAILROAD PROGRAMMING Happy Path (Continue) Error Case (Skip) No Effect (Afterwards)
E I T H E R / R E S U LT C A R R I E R D ATA
E I T H E R / R E S U LT I N S TA N C E S
E I T H E R / R E S U LT USE
E I T H E R / R E S U LT USE
WRITER
WRITER 🖊 I N S P E C T A B L E , D A TA - O R I E N T E D L O G G I N G
WRITER MONAD 🖊
WRITER MONAD 🖊 Log Program
WRITER MONAD 🖊 Log Program
WRITER C A R R I E R D ATA
WRITER I N S TA N C E S
WRITER USE
READER
READER 📚 CONFIG OR CONTEXT INJECTION
READER MONAD
READER MONAD Context Program
READER MONAD Context Program
READER C A R R I E R D ATA
READER I N S TA N C E S
READER USE
MONADS
MONADS 🚀 A LOT OF POWER FOR A HANDFUL OF FUNCTIONS
https://fission.codes https://tools.fission.codes 8 THANK YOU, MALMÖ 🎉 brooklyn@fission.codes g i t h u b . c o m /e x p e d e @expede
