paf31

Introduction

At DICOM Grid, we recently made the decision to use Haskell for some of our newer projects, mostly small, independent web services. This isn't the first time I've had the opportunity to use Haskell at work - I had previously used Haskell to write tools to automate some processes like generation of documentation for TypeScript code - but this is the first time we will be deploying Haskell code into production.

Over the past few months, I have been working on two Haskell services:

• A reimplementation of an existing socket.io service, previously written for NodeJS using TypeScript.
• A new service, which would interact with third-party components using standard data formats from the medical industry.

I will write here mostly about the first project, since it is a self-contained project which provides a good example of the power of Haskell. Moreover, the proces

paf31

PureScript Unsession

Introduction

• This doc - https://gist.github.com/paf31/80fdea566b0f7cfefadd
• About me
• About you
• About PureScript
  • Features
• Type Inference

paf31

let isEven :: Number -> Boolean
    isEven 0 = false
    isEven 1 = false
    isEven 2 = true
    isEven n = isEven(n-1)

paf31

module Main where

import qualified Language.PureScript as P

main = interact compile
  where
  compile text =
    case P.runIndentParser "" P.parseModules "module Prelude where\nmain = \"Hello World\"" of
      Left err -> show err
      Right modules ->

paf31

module LLC

consume : Nat -> List (Maybe Nat) -> List (Maybe Nat)
consume vid (Nothing :: vs) = Nothing :: consume vid vs
consume vid (Just v :: vs) with (vid == v)
  | True = Nothing :: vs
  | False = Just v :: consume vid vs

data Lolli : Type -> Type -> Type where
  mkLolli : (a -> b) -> Lolli a b

paf31

module Main where

foreign import data Exists :: (* -> *) -> *

foreign import mkExists
  "function mkExists(fa) {\
  \  return fa;\
  \}" :: forall f a. f a -> Exists f
  
foreign import runExists

paf31

module Main where

import Debug.Trace

data Trampoline a = Done a | More ({} -> Trampoline a)

instance functorTrampoline :: Functor Trampoline where
  (<$>) f (Done a) = Done (f a)
  (<$>) f (More k) = More $ \_ -> f <$> k {}
  

paf31

module Deriv

import Control.Isomorphism

--
-- A type constructor df is the derivative of the type constructor f if for all x and e there exists d such
-- such that
--
-- f (x + e) ~ f x + e * (df x) + e^2 * d
--

paf31

"use strict";

// module UnderscoreFFI

exports.map = function(f) {
  return function (arr) {
    return require('underscore').map(arr, f);
  };
};

paf31

var main = function __do() {
  var _4 = 1;
  var _3 = 1;
  return (function () {
    while (_ps.Prelude.pure(_ps.Prelude.applicativeFromMonad(_ps.Control_Monad_Eff.monadEff({})))(true)()) {
      (function __do() {
        var _2 = _4;
        var _1 = _3;
        _3 = _2 + _1;
        _4 = _1;