Let's talk about PureScript

Presentation at Frontend Meetup Riga, August 2016.

Transcript

1. an exciting trip
   through history
   prelude
   

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2. 1936
   Lambda Calculus is
   born
   

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3. 1990
   A bunch of smart
   people start working
   Haskell
   

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4. 1995
   Brendan Eich is hired
   by NetScape to write
   Scheme for the
   browser
   

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5. Spoiler alert:
   He doesn't write a
   Scheme for NetScape
   

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7. You shouldn't be
   sad.
   

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8. Maybe those
   functional dudes got
   something right.
   

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9. let's talk about
   purescript
   Kārlis Lauva
   @skazhy
   frontend rīga meetup, 2016
   

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10. Hello.
    I write Clojure and
    dabble with other
    things
    This is not a monad
    tutorial
    This is, like, my
    opinion
    

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11. So, Haskell for
    the browser, eh
    

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12. module Main where
    import Prelude
    import Control.Monad.Eff
    import Control.Monad.Eff.Console
    sup :: String -> String
    sup g = "sup, " ++ g
    main :: forall e. Eff (console :: CONSOLE | e) Unit
    main = do
    log $ sup "world"
    

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14. (function(exports) {
    "use strict";
    var Prelude = PS["Prelude"];
    var Control_Monad_Eff = PS["Control.Monad.Eff"];
    var Control_Monad_Eff_Console = PS["Control.Monad.Eff.Console"];
    var sup = function (g) { return "sup, " + g; };
    var main = Control_Monad_Eff_Console.log(sup("world"));
    exports["main"] = main;
    exports["sup"] = sup;;
    })(PS["Main"] = PS["Main"] || {});
    PS["Main"].main();
    

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15. Y
    

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16. turns out, functional
    programming languages
    are really useful for
    web things
    

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17. but javascript too
    can be purely
    functional
    

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19. let's
    discuss the
    bad parts
    

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20. [Object object]
    

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21. an *actual*
    type system
    

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22. purescript makes
    this example boring
    

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23. like, really boring
    

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24. sketchy
    branching
    

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27. pattern
    matching
    

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28. data Behavior = KillHumans | BeNiceToHumans
    type Robot = { naughty :: Boolean }
    interactWithHumans :: Robot -> Behavior
    interactWithHumans { naughty: true } = KillHumans
    interactWithHumans { naughty: false } = BeNiceToHumans
    

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29. data Behavior
    = KillAllHumans
    | BeNiceToHumans
    | KillOnlyVapers
    type Robot = { niceness :: Int }
    interactWithHumans :: Robot -> Behavior
    interactWithHumans { niceness: 0 } = KillAllHumans
    interactWithHumans { niceness: 1 } = KillOnlyVapers
    interactWithHumans _ = BeNiceToHumans
    

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30. callback hell
    

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31. monads
    

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32. fetchRobots(function(response) {
    assembleFleet(function(robots) {
    if (robots)
    return robots;
    }, function(error { .. });
    }, function(error) {... });
    

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33. data RobotArmy = Army (List Robot)
    fetchRobots = do
    robotParts <- get "/robotParts"
    robots <- assembleFleet robotParts
    return $ Army robots
    

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35. does purescript
    survive
    in the real
    world?
    

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36. yes.
    

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38. ecosystem
    and tooling
    

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39. psc
    short for "purescript compiler"
    

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40. modules
    managed via bower
    

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41. • build tool => pulp
    • hoogle for purescript => pursuit
    

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42. purescript
    -
    javascript
    teamwork
    

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43. back to killer
    robots
    

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44. data Behavior = KillHumans | BeNiceToHumans
    instance showBehavior :: Show Behavior where
    show KillHumans = "kill all humans11"
    show BeNiceToHumans = "humans, you are pretty tite"
    type Robot = { naughty :: Boolean }
    interactWithHumans :: Robot -> Behavior
    interactWithHumans { naughty: true } = KillHumans
    interactWithHumans { naughty: false } = BeNiceToHumans
    safeInteract :: Boolean -> String
    safeInteract x =
    show $ interactWithHumans { crazyMurderer : x }
    

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45. PS.Main.safeInteract(isCrazyMurderingRobot)();
    

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46. but will
    purescript
    react?
    

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47. yes.
    

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48. ok, so what
    have we
    learned
    

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49. so should we all
    switch to
    purescript today?
    

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50. not _all_ of us
    

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51. most of the internet
    runs on vanilla
    javascript just fine
    (for years)
    

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54. go check it out
    hack cool things
    

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55. • purescript.org
    • karlis.me
    

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56. thanks
    

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