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Let's talk about PureScript
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Kārlis Lauva
August 17, 2016
Programming
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78
Let's talk about PureScript
Presentation at Frontend Meetup Riga, August 2016.
Kārlis Lauva
August 17, 2016
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Transcript
an exciting trip through history prelude
1936 Lambda Calculus is born
1990 A bunch of smart people start working Haskell
1995 Brendan Eich is hired by NetScape to write Scheme
for the browser
Spoiler alert: He doesn't write a Scheme for NetScape
2016
You shouldn't be sad.
Maybe those functional dudes got something right.
let's talk about purescript Kārlis Lauva @skazhy frontend rīga meetup,
2016
Hello. I write Clojure and dabble with other things This
is not a monad tutorial This is, like, my opinion
So, Haskell for the browser, eh
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"
None
(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();
Y
turns out, functional programming languages are really useful for web
things
but javascript too can be purely functional
None
let's discuss the bad parts
[Object object]
an *actual* type system
purescript makes this example boring
like, really boring
sketchy branching
None
None
pattern matching
data Behavior = KillHumans | BeNiceToHumans type Robot = {
naughty :: Boolean } interactWithHumans :: Robot -> Behavior interactWithHumans { naughty: true } = KillHumans interactWithHumans { naughty: false } = BeNiceToHumans
data Behavior = KillAllHumans | BeNiceToHumans | KillOnlyVapers type Robot
= { niceness :: Int } interactWithHumans :: Robot -> Behavior interactWithHumans { niceness: 0 } = KillAllHumans interactWithHumans { niceness: 1 } = KillOnlyVapers interactWithHumans _ = BeNiceToHumans
callback hell
monads
fetchRobots(function(response) { assembleFleet(function(robots) { if (robots) return robots; }, function(error
{ .. }); }, function(error) {... });
data RobotArmy = Army (List Robot) fetchRobots = do robotParts
<- get "/robotParts" robots <- assembleFleet robotParts return $ Army robots
None
does purescript survive in the real world?
yes.
None
ecosystem and tooling
psc short for "purescript compiler"
modules managed via bower
• build tool => pulp • hoogle for purescript =>
pursuit
purescript - javascript teamwork
back to killer robots
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 }
PS.Main.safeInteract(isCrazyMurderingRobot)();
but will purescript react?
yes.
ok, so what have we learned
so should we all switch to purescript today?
not _all_ of us
most of the internet runs on vanilla javascript just fine
(for years)
None
None
go check it out hack cool things
• purescript.org • karlis.me
thanks