Presto - 10x Faster Mobile App Dev with PureScript

Transcript

1. 10x Faster
   Mobile App Dev
   with PureScript
   Presto.
   

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2. ● Built large scale systems at Juspay, Amazon,
   Trilogy serving millions of users
   ● A convert to PureScript from Clojure / JavaScript
   ● Passionate about building Creation tools
   Hello!
   I’m Vimal Kumar, CEO of Juspay
   

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3. Why do commercial apps take months
   to develop and millions of $$ to
   maintain?
   PROBLEM
   

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4. Why are Apps hard?
   Unnatural programming model for
   Business Logic
   ● Event based model complicates transactional apps
   ● No clarity of flow of control - too many jumps
   ● Can’t compose flows, smaller to larger, due to async nature
   

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5. Why are Apps hard?
   Frameworks focus on Getting started quick;
   Not on fundamentals to Control complexity
   ● Complexity of serious apps is exponentially increasing.
   ● Need a strong theory like Functional Programming / Category
   theory with extreme focus on composition.
   ● Hard theories need years of investment to get practical advantage.
   

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6. Why are Apps hard?
   Fragmented Architecture, Need Unification
   ● Frontend, Backend, Persistence, External service integration,
   Analytics, Business Logic, Infrastructure.
   ● All are handled in different ways. They can be unified with a
   few simple building blocks.
   

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7. Presto’s vision is to enable
   Freshers/PMs build and maintain apps
   with 10x less time and effort.
   It needn’t be this way!
   

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8. How?
   ● Conversational UX DSL
   ● Business Flows as Goal Trees
   ● PureScript - Pure FP, Category Theory
   ● Unify, Only 3 Blocks, UI | Flows | Data
   

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9. UX Flows as Conversational DSL
   User System
   App
   Welcome
   Tell
   Ask
   Ask-Options
   Ask-Search
   Ask-Confirm
   Thank
   Delight
   Suggest
   Cross Sell
   Notify
   Fetch
   Detect
   Search
   Commit
   Track
   SetTimer
   Etc..
   App
   The App
   Weaves a.
   Conversation
   between User
   & System
   towards a
   Goal
   Goal
   

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10. Business Logic as Goal Trees
    ● Composable Goals!
    ● Understandable to
    non-tech - Designers,
    Product Managers
    Introduce Verify Mobile Create VPA Goal: BHIM Onboarding
    UI: Step 1 Help
    UI: Step 2 Help
    UI: Success
    OR
    Verify Mobile
    With OTP
    Verify Mobile
    Sending SMS
    API: Trigger OTP
    Poll SMS Inbox
    for OTP
    More steps
    Tree extends
    here…
    Local API: Send
    SMS Code
    Poll Server for
    SMS Code
    UI: Success
    More steps
    Tree extends
    here…
    More steps
    Tree extends
    here…
    UI: Welcome
    UI: Ask Mobile
    

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11. Welcome Dilip to the app
    Ask to pay the DTH bill (why not give some incentive!) >
    Ask to choose DTH Operator. If a lot, let him search >
    Ask for his Customer ID. Show HELP on where to find the Customer ID >
    Fetch his Customer Name and latest due bill amount :: LOAD >
    Show the bill details and Ask to pay
    SubFlow Collect_UPI_MPIN
    Commit the payment and Show confirmation status.
    Cross Sell Ask if he’d like to set up Auto-deduct OR Payment reminder for future bills >
    Thank Dilip.
    Goal Tree as a Narrative
    

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12. DSL Goal Tree - Code Walkthrough
    

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13. PureScript - Pure FP
    ● Composition, State Management, Conciseness and Clarity
    ● CPS (Continuation passing style) for the DSL Goal Trees
    ● Choice of PureScript - Best of Haskell and JavaScript.
    ● Category Theory - Functors / Monads / Applicatives
    

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14. Just 3 Building Blocks - Unify
    ● UI Structure - Visual Components like React
    ● Goal Tree - Flows as Pure Functions
    ○ Represents the entire business logic
    ○ Unified Backend and Frontend
    ● Data as Types
    ○ Single set of types for Frontend, Backend, UI, Storage
    ○ Types mapped to DB data model
    

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15. Why PureScript and CPS?
    LANGUAGE OPTIONS
    ARCHITECTURE OPTIONS
    PureScript GhcJS ClojureScript
    Haskell Like
    + Strong FP - Focus on Purity,
    Composition, Concise.
    + Types - Few errors, Easy refactoring
    JS Integration
    + Solid and easy JS FFI
    + JS Code Small & Reliable
    - New and evolving
    + Implements all Haskell’s
    features and access to most
    Haskell Libraries.
    - Large size JS and not so
    reliable runtime
    + Is a Lisp!
    + Strong Developer community
    + Proven runtime
    - Lacks Types
    - Lacks strong math / category
    theory foundation of Haskell
    CPS (Continuation Passing) Elm Architecture / Redux Pure FRP
    Maps directly to UX flows / flows as
    conversion funnel.
    Global state complicates
    transactional flows vs CPS manages
    local state in stack
    More general than CPS but
    complicates UX flows. Presto will add
    FRP support in future
    

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16. How is this 10X?
    ● Reuse of Lego Blocks: UI / Flow / Data components become
    extremely reusable across apps as we use Pure FP techniques.
    ● FP and Types guarantee Reliability for Free, minimizes testing.
    ● The DSL - Unifies Product / Dev and Design teams, improves
    clarity & removes communication overhead.
    ● Unified UI code for Android / iOS / Progressive Webapp / Desktop
    Web removes necessity for multiple UI dev teams
    ● Unified frontend / backend removes need for separate mobile and
    backend teams
    

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17. Apps in Production
    UPI SDK for top Apps UPI for Petroleum New Juspay Safe
    Potential for 100M+ users
    

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18. Next Steps
    School of Functional Programming
    

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19. Next Steps
    Visual Programming
    ● Auto generate UI components from design - Sketch plugin
    ● UX Goal Tree as an editable Fishbone diagram
    

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20. Thanks!
    Want to contribute? Just mail us at
    presto@juspay.in
    

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