Functional programming - part 1

Learning the skill "Distinguish Actions, Calculations and Data".

Transcript

1. Functional programming
   James Su - 2022/04/15
   Sur
   f
   ing in the changing world
   

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2. What is functional
   programming?
   

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3. Functional programming
   in Wikipedia
   • A programming paradigm characterized by mathematical functions and
   the avoidance of side e
   ff
   ects.
   
   
   • A programming style that uses only pure functions without side e
   ff
   ects.
   

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4. Side effects
   Anything a function does
   other than returning a value
   

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5. Pure functions
   Don't have any side e
   ff
   ects.
   Given the same arguments,
   return the same result.
   
   
   

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6. Bene
   f
   its of pure functions
   • Don't depend on how many times and when they are run.
   
   
   • Results are predictable, easier to understand and control.
   
   
   • Compilers can optimize for predictable things.
   

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7. But, we need side effects
   in real world
   • Send an email
   
   
   • Reading a
   f
   ile
   
   
   • Writing to database
   
   
   • Making a web request
   
   
   • Blinking a light
   

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8. Functional programming
   in real world
   • A set of skills, concepts and principles:
   
   
   • Distinguishing actions, calculations, and data
   
   
   • Staying immutable in a mutable language
   
   
   • ... and more
   
   
   • They are valuable and regardless of what language you use.
   

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9. Distinguishing
   
   
   Actions, Calculations and Data
   

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10. Actions
    • Depend on how many times or when it is run.
    
    
    • Also called: functions with side e
    ff
    ects.
    
    
    • Examples:
    
    
    • Send an email
    
    
    • Read from a database
    

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11. Calculations
    • Computations from input to output.
    
    
    • Also called: pure functions, mathematical functions.
    
    
    • Examples:
    
    
    • Find the users to send email
    
    
    • Calculate total price in shopping cart
    

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12. Data
    • Facts about events.
    
    
    • Their meanings are di
    ff
    erent according to situations.
    
    
    • Examples:
    
    
    • An email address
    
    
    • A user structure
    
    
    • A dinner receipt
    

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13. Bene
    f
    its of distinguishing actions, calculations and data
    • Thinking about a problem
    
    
    • Clarify parts that need special attention (actions)
    
    
    • What data we will need to capture (data)
    
    
    • What decisions we will need to make (calculations)
    
    
    • Coding a solution
    
    
    • Write code with immutable in mind: data > calculations > actions.
    
    
    • Reading code
    
    
    • Refactor the code to better separate from actions, calculations and data.
    

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14. Thinking a problem
    

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15. Thinking a problem
    

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16. Strati
    f
    ied design
    Organizing code by
    
    
    "rate of change"
    

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17. Why functional programming
    popular these days?
    

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18. Functional languages
    • Erlang
    
    
    • WhatsApp - Why WhatsApp Only Needs 50 Engineers for Its 900M Users
    
    
    • Elixir
    
    
    • Discord - How Discord Scaled Elixir to 5,000,000 Concurrent Users
    
    
    • Apple - Working on APIs towards carbon neutral by 2030
    
    
    • Clojure
    
    
    • Roam Research - State of Clojure 2021 Results
    
    
    • Elm
    
    
    • https://github.com/jah2488/elm-companies
    
    
    • Blazing Fast HTML
    

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20. We are in a world
    programs run on multicores and distributed devices
    • Functional programs run in parallel.
    
    
    • Compilers optimize for functional programs.
    

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22. Q & A
    

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