purescript.md

PureScript

What is it?

• compiles to js
• haskell-inspired type system (with some improvements!)
• no runtime (unlike elm, ghcjs, etc)
• focus on readable and debuggable js

Installing

npm i -g purescript pulp

PureScript:

• psc
• psci
• ...

Pulp:

• pulp init
• pulp build
• pulp test
• pulp docs
• pulp server

Let's compile some code!

x :: Number
x = 5.0

y :: Int
y = 5

import Prelude ((+))

add :: Number -> Number -> Number
add x y = x + y

import Prelude ((+))

add :: Int -> Int -> Int
add x y = x + y

data Maybe a = Nothing | Maybe a

data Maybe a = Nothing | Maybe a

greeting :: Maybe String
greeting = Just "hello."

silence :: Maybe String
silence = Nothing

data Direction
  = North
  | South
  | East
  | West

class Reversible a where
  reverse :: a -> a

instance reversibleDirection :: Reversible Direction where
  reverse North = South
  reverse South = North
  reverse East = West
  reverse West = East

mirror :: forall a. (Reversible a) => a -> Tuple a a
mirror a = Tuple a (reverse a)