Friendly Elm (怖くないElm)

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1 Friendly Elm 2016/11/04 Yosuke Torii

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2 怖くない Elm 2016/11/04 Yosuke Torii

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3 Who I am * Yosuke Torii * @jinjor * Works Applications Co., Ltd. * Contributor of Elm

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4 Who I am * Yosuke Torii * @jinjor * Works Applications Co., Ltd. * Contributor of Elm

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5 Introduction to Elm

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6 Q. How many folks have heard of Elm? Q. How many folks have written any piece of code in Elm?

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7 Q. How many folks have heard of Elm? 45 Q. How many folks have written any piece of code in Elm? 5

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8 Elm is a FP Language * Generates JavaScript * Static Typing * Everything is Immutable * Fast rendering via Virtual DOM

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9 Elm = Language + Framework VS No more JavaScript Fatigue!

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10 How strong is Elm's type? Strong Haskell Elm Scala Java TypeScript JavaScript Ruby Python Flow

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11 How strong is Elm's type? Strong Haskell Elm Scala Java TypeScript JavaScript Ruby Python Flow No Runtime Errors

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12 Experiencing Elm in Practice

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13 Making a seat arrangement app

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14 Lots of complex UIs! * Copy / Cut / Paste * Undo / Redo * Selecting * Dragging * Zooming * Searching * Context Menu * Clipboard * Keyboard Shortcuts * Auto Saving * Co-editing

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15 After several months... * Started using in our company (Still continuing development) * Open Source (WorksApplications/office-maker)

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16 Stats

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17 Stats 9,400 lines of Elm code

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18 Stats 9,400 lines of Elm code 0 runtime errors

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19 Refactoring with confidence * Regressions rarely happen * No fear with large/frequent changes * No untouchable code any more!

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20 But... it looks difficult to learn

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21 Elm is friendly for FP beginners ✓ FP for Front End developer ✗ Front End for FP programmer

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22 No need to learn Haskell VS * Monad and other terminologies from Category theory * Type classes in general use The most difficult parts do not exist in Elm

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23 Elm is getting even simpler 0.16 (2015/11) * More friendly compile error messages * Remove some record operations * Remove multi-way if 0.17 (2016/05) * Remove Signals (which was the most defficult) * Simplify main function 0.18 (2016/11) * More friendly compile error messages * Remove backticks * Remove [1..4] syntax * Remove primes in variable name

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24 Elm is getting even simpler 0.16 (2015/11) * More friendly compile error messages * Remove some record operations * Remove multi-way if 0.17 (2016/05) * Remove Signals (which was the most defficult) * Simplify main function 0.18 (2016/11) * More friendly compile error messages * Remove backticks * Remove [1..4] syntax * Remove primes in variable name