Elm kyivfprog 2015
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The document introduces Elm, a functional programming language that compiles to JavaScript. It has a focus on simplicity, robustness, and helping developers avoid bugs. Some key points about Elm include its functional, immutable, and statically typed nature; built-in support for functional reactive programming; use for building rich user interfaces; and emphasis on easy refactoring and adding new features. The document also discusses Elm's syntax, type system, record handling, approach to avoiding runtime exceptions, architecture for user interface apps, and ecosystem of tools.
![Extensible records
point = { x = 3, y = 4 } -- create a record
point.x -- access field
map .x [point,{x=0,y=0}] -- field access function
{ point - x } -- remove field
{ point | z = 12 } -- add field
{ point - x | z = point.x } -- rename field
{ point - x | x = 6 } -- update field
{ point | x <- 6 } -- nicer way to update a field
{ point | x <- point.x + 1
, y <- point.y + 1 } -- batch update fields](https://image.slidesharecdn.com/elmkyivfprog2015-151031130730-lva1-app6891/85/Elm-kyivfprog-2015-11-320.jpg)
![let list = [1, 2, 3];
let first = (lst) => lst[0];
let doubleFirst = (lst) => first(list) * 2
list = [1, 2, 3]
first lst = List.get 0 list
doubleFirst lst = (first lst) * 2
js Elm](https://image.slidesharecdn.com/elmkyivfprog2015-151031130730-lva1-app6891/85/Elm-kyivfprog-2015-14-320.jpg)
![let list = [1, 2, 3];
let first = (lst) => lst[0];
let doubleFirst = (lst) => first(list) * 2
list = [1, 2, 3]
first lst = List.get 0 list
doubleFirst lst = (first lst) * 2
js Elm](https://image.slidesharecdn.com/elmkyivfprog2015-151031130730-lva1-app6891/85/Elm-kyivfprog-2015-15-320.jpg)
![let list = [1, 2, 3];
let first = (lst) => lst[0];
let doubleFirst = (lst) => first(list) * 2
list = [1, 2, 3]
first list = get 0 list
doubleFirst list = case first list of
Just n -> Just (n * 2)
Nothing -> Nothing
js Elm](https://image.slidesharecdn.com/elmkyivfprog2015-151031130730-lva1-app6891/85/Elm-kyivfprog-2015-16-320.jpg)
![let list = [1, 2, 3];
let first = (lst) => lst[0];
let doubleFirst = (lst) => first(list) * 2
But it doesn’t fail if []?](https://image.slidesharecdn.com/elmkyivfprog2015-151031130730-lva1-app6891/85/Elm-kyivfprog-2015-17-320.jpg)
Elm kyivfprog 2015
- 2. Mostovenko Alexander ● fullstack engineer in datarobot ● for inspiration: haskell, elm, purescript ● for job: python, javascript ● twitter - https://twitter.com/MostovenkoA ● github - https://github.com/AlexMost
- 3. Elm in general ● Functional (ML-like, compiles to js). ● Immutable data structures. ● Statically typed. (ADT, type inference). ● With FRP in mind (Signals are built in language). ● Created for building rich UI apps.
- 4. Idea Why another to-js lang ?
- 9. The main focus ● Easy to get started. ● Simple and clean syntax. ● Focus on business logic (no frameworks holy wars e.t. c.). ● Simple refactor. ● Simple add features. ● Less bugs in production.
- 10. Minimal but powerful syntax type alias Model = Int -- UPDATE type Action = Increment | Decrement update : Action -> Model -> Model update action model = case action of Increment -> model + 1 Decrement -> model - 1 ● Comments ● Literals ● Lists ● Conditionals ● Union Types ● Records ● Functions ● Infix Operators ● Let Expressions ● Applying Functions ● Mapping with (<~) and (~) ● Modules ● Type Annotations ● Type Aliases ● JavaScript FFI
- 11. Extensible records point = { x = 3, y = 4 } -- create a record point.x -- access field map .x [point,{x=0,y=0}] -- field access function { point - x } -- remove field { point | z = 12 } -- add field { point - x | z = point.x } -- rename field { point - x | x = 6 } -- update field { point | x <- 6 } -- nicer way to update a field { point | x <- point.x + 1 , y <- point.y + 1 } -- batch update fields
- 12. Extensible records sumCoordinates: {a | x: Int, y: Int} -> Int sumCoordinates {x, y} = x + y http://research.microsoft.com/pubs/65409/scopedlabels.pdf
- 14. let list = [1, 2, 3]; let first = (lst) => lst[0]; let doubleFirst = (lst) => first(list) * 2 list = [1, 2, 3] first lst = List.get 0 list doubleFirst lst = (first lst) * 2 js Elm
- 15. let list = [1, 2, 3]; let first = (lst) => lst[0]; let doubleFirst = (lst) => first(list) * 2 list = [1, 2, 3] first lst = List.get 0 list doubleFirst lst = (first lst) * 2 js Elm
- 16. let list = [1, 2, 3]; let first = (lst) => lst[0]; let doubleFirst = (lst) => first(list) * 2 list = [1, 2, 3] first list = get 0 list doubleFirst list = case first list of Just n -> Just (n * 2) Nothing -> Nothing js Elm
- 17. let list = [1, 2, 3]; let first = (lst) => lst[0]; let doubleFirst = (lst) => first(list) * 2 But it doesn’t fail if []?
- 18. NaN
- 19. Signals
- 20. UI app architecture ● Unidirectional data flow ● Virtual dom ● FRP based approach
- 21. The Elm architecture https://github.com/evancz/elm-architecture-tutorial/ ● Model (State) ● Update ● View
- 23. Ecosystem ● Package manager ● Packege catalog - http://package.elm-lang.org/ ● build tool (elm-make, elm-reactor) ● time travel debugger ● hot swap
- 24. Elm package manager Semantic versioning (1.0.0 - major.minor.patch) elm-package bump - new version can see diff - elm-package diff 1.0.1
- 25. Time travel debugger mario demo - http://debug.elm-lang.org/edit/Mario.elm
- 27. Elm exists in production
- 28. Demo 2048 - https://github.com/AlexMost/2048 more demos - http://elm-lang.org/examples
- 29. :)