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@jenny-codes Functional programming for fun and profit!!

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@jenny_codes https://github.com/readme/featured/functional-programming

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@jenny_codes Source: https://youtu.be/ADqLBc1vFwI

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@jenny_codes Source: https://giphy.com/gifs/emoji-idk-thinking-3o7buirYcmV5nSwIRW What is functional programming?

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@jenny_codes Source: https://giphy.com/gifs/emoji-idk-thinking-3o7buirYcmV5nSwIRW What is functional programming? Should I care about it if I just want to write Ruby code?

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Functional programming helps us write better Ruby code

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@jenny_codes Jenny Shih / 施靜樺

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@jenny_codes Jenny Shih / 施靜樺 🇹🇼 Taiwan -> 🇨🇦 Canada 💎 💧 https://codecharms.me

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Programming paradigms A way to classify programming languages based on their features

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@jenny_codes Programming paradigms • Object Oriented Programming (OO) • Functional Programming (FP)

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Mental model

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@jenny_codes Value Time Behavior A program

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@jenny_codes

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@jenny_codes Value Behavior

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@jenny_codes

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@jenny_codes Time

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@jenny_codes Value Time Behavior A program State

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@jenny_codes Object An OO program Value Behavior Time Time

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@jenny_codes An OO program Object Value Behavior Object Value Behavior Object Value Behavior Time Time Time Time Time Time

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@jenny_codes A FP program Value Time Behavior

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@jenny_codes A FP program Value Time Behavior

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Immutability

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Immutability Don’t change a value once you initialize it.

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@jenny_codes Immutability

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@jenny_codes Immutability

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@jenny_codes Immutability

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@jenny_codes Immutability

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@jenny_codes Source: https://giphy.com/gifs/emoji-idk-thinking-3o7buirYcmV5nSwIRW Why?

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@jenny_codes Immutability: Why?? • Peace of mind

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@jenny_codes Immutability: Why??

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@jenny_codes Immutability: Why?? • Peace of mind

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@jenny_codes Immutability: Why?? • Peace of mind • Eliminate shared state

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@jenny_codes Immutability: Why?? • Peace of mind • Eliminate shared state

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@jenny_codes Immutability: How???

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@jenny_codes Immutability: How??? • Provide a good reason for every value mutation.

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@jenny_codes Immutability: How??? • Provide a good reason for every value mutation. • Use tools

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@jenny_codes

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@jenny_codes https://dry-rb.org/

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@jenny_codes Immutability: How??? • Provide a good reason for every value mutation. • Use tools • `dry-struct`: https://dry-rb.org/gems/dry-struct/main/

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@jenny_codes Immutability: How??? • Provide a good reason for every value mutation. • Use tools • `dry-struct`: https://dry-rb.org/gems/dry-struct/main/ • `Data.de fi ne` in Ruby

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@jenny_codes

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@jenny_codes

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@jenny_codes https://dev.to/baweaver/new-in-ruby-32-datade fi ne-2819

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@jenny_codes Immutability: How??? • Provide a good reason for every value mutation. • Use tools • `dry-struct`: https://dry-rb.org/gems/dry-struct/main/ • `Data.de fi ne` in Ruby

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@jenny_codes A FP program Value Time Behavior

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@jenny_codes A FP program Value Time Behavior Immutable data

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@jenny_codes A FP program Value Time Behavior Immutable data

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Pure functions

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes Source: https://giphy.com/gifs/emoji-idk-thinking-3o7buirYcmV5nSwIRW Why?

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@jenny_codes “The problem with OO languages is they’ve got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle.” – Joe Armstrong, Creator of Erlang Pure functions: Why??

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@jenny_codes “The problem with OO languages is they’ve got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle.” – Joe Armstrong, Creator of Erlang Pure functions: Why??

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@jenny_codes Pure functions: Why?? No implicit environment!! Source: https://thenounproject.com/icon/forest-5299391/ Source: https://thenounproject.com/icon/monkey-298282/

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@jenny_codes Pure functions: Why?? No implicit environment!! Source: https://thenounproject.com/icon/forest-5299391/ Source: https://thenounproject.com/icon/monkey-298282/

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@jenny_codes Pure functions: Why?? No implicit environment!! 🤯

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@jenny_codes Pure functions: Why?? No implicit environment!!

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@jenny_codes Pure functions: Why?? No implicit environment!! 🤘

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@jenny_codes Pure functions: Why?? No implicit environment!! 🤘🐛 🔪

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@jenny_codes Pure functions: Why?? No implicit environment!! 🤘🐛 🔪 🧪

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@jenny_codes Pure functions: Why?? No implicit environment!! 🤘🐛 🔪 🧪 ✅

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@jenny_codes Pure functions: Why?? No implicit environment!! 🤘🐛 🔪 🧪 ✅ ✌

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@jenny_codes Pure functions: Why?? No implicit environment!! 🤘🐛 🔪 🧪 ✅ ✌ Source: https://www.ktiv.com/2022/10/07/nobel-peace-prize-awarded-human-rights-advocates/

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@jenny_codes Pure functions: How???

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@jenny_codes Pure functions: How??? • Parameterization/Dependency Injections

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: Parameterization

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@jenny_codes Pure functions: How??? • Parameterization/Dependency Injections • Transformation instead of mutation

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@jenny_codes Pure functions: Transformation over Mutation

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@jenny_codes Pure functions: Transformation over Mutation

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@jenny_codes Pure functions: Transformation over Mutation

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@jenny_codes 1. Only depends on its input argument 2. Does not mutate states (no side effects) A pure function

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@jenny_codes A pure function 1. Only depends on its input argument ✅ 2. Does not mutate states (no side effects)

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@jenny_codes A pure function 1. Only depends on its input argument ✅ 2. Does not mutate states ✅ (no side effects)

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@jenny_codes A FP program Value Time Behavior Immutable data

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@jenny_codes A FP program Value Time Behavior Immutable data Pure functions

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@jenny_codes A FP program Value Time Behavior Immutable data Pure functions

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Concurrency

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@jenny_codes An OO program Object Value Behavior Object Value Behavior Object Value Behavior Time Time Time Time Time Time

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@jenny_codes An OO program Object Value Behavior Object Value Behavior Object Value Behavior Time Time Time Time Time Time Global Interpreter Lock 🔐

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@jenny_codes A FP program Value Time Behavior Immutable data Pure functions Concurrency 💯

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@jenny_codes Elixir’s concurrency model: Actors Actor / Process Actor / Process Actor / Process

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@jenny_codes Elixir’s concurrency model: Actors Thread Thread Thread

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@jenny_codes “It’s multi-core age today. Concurrency is very important. With Ractor, along with Async Fiber, Ruby will be a real concurrent language.” — Matz Ruby’s concurrency abstraction: Ractor https://www.ruby-lang.org/en/news/2020/12/25/ruby-3-0-0-released/

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@jenny_codes Ractor Ractor Ractor ︴︴︴ ︴︴︴ ︴︴︴ Ruby’s concurrency abstraction: Ractor ︴︴︴= threads

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@jenny_codes Ractor Ractor Ractor 🔐 🔐 🔐 ︴︴︴ ︴︴︴ ︴︴︴ 🔐 = Global Interpreter Lock Ruby’s concurrency abstraction: Ractor ︴︴︴= threads

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@jenny_codes Ractor Ractor Ractor 🔐 🔐 🔐 ︴︴︴ ︴︴︴ ︴︴︴ 🔐 = Global Interpretation Lock Ruby’s concurrency abstraction: Ractor ︴︴︴= threads ❓

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@jenny_codes

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@jenny_codes A FP program Value Time Behavior Immutable data Pure functions Concurrency

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Recap

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@jenny_codes We are defined not so much by what we can do, but what we don’t do.

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@jenny_codes A FP program Value Time Behavior Immutable data Pure functions Concurrency

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@jenny_codes A FP program Value Time Behavior Immutable data Pure functions Concurrency

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@jenny_codes A FP program Value Time Behavior Immutable data Pure functions Concurrency

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@jenny_codes A FP program Value Time Behavior Immutable data Pure functions Concurrency

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Functional programming helps us write better Ruby code

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@jenny_codes Resources: Functional programming mental model • Jose Valim’s ElixirConf 2017 Keynote by Jose Valim • Are we there yet by Rich Hickey • The language of programming by Anjana Vakil • Value Object by Martin Fowler

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@jenny_codes Resources: Functional programming architecture (That I didn’t get to talk about because I’d get too excited and run overtime) • Functional Architecture for the Practical Rubyist by Tim Riley • Functional web with Ruby by Luca Luigi • Boundaries by Gary Bernhardt • The Hanami Ruby framework • (Book) Domain Modelling Made Functional by Scott Wlaschin

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@jenny_codes Resources: Ruby docs • https://ruby-doc.org/core-3.2.0_preview2/Ractor.html • https://scoutapm.com/blog/ruby-ractor • https://dev.to/baweaver/new-in-ruby-32-datade fi ne-2819 • https://github.com/ruby/ruby/pull/6353