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Presto - 10x Faster Mobile App Dev with PureScript

Vimal Kumar
September 08, 2017
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Presto - 10x Faster Mobile App Dev with PureScript

Vimal Kumar

September 08, 2017
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  1. • 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
  2. 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
  3. 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.
  4. 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.
  5. Presto’s vision is to enable Freshers/PMs build and maintain apps

    with 10x less time and effort. It needn’t be this way!
  6. How? • Conversational UX DSL • Business Flows as Goal

    Trees • PureScript - Pure FP, Category Theory • Unify, Only 3 Blocks, UI | Flows | Data
  7. 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
  8. 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
  9. 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
  10. 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
  11. 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
  12. 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
  13. 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
  14. Apps in Production UPI SDK for top Apps UPI for

    Petroleum New Juspay Safe Potential for 100M+ users
  15. Next Steps Visual Programming • Auto generate UI components from

    design - Sketch plugin • UX Goal Tree as an editable Fishbone diagram