srdjan

Making Toys with F# - A Small Elm-like DSL in F#

I've been working on a talk about the virtues of building toy examples for the purpose of communicating ideas with simple interactive examples.

The toys I talk about in my presentation are based my interest in tools that allow programmers to quickly build web applications that allow them to explore their architecture. So to kickstart this series off, I want to introduce a simple

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module Main where

-- | JSON is an incredibly simple format. Even its lists are untyped.
-- | As with all languages, functional programming encourages us to
-- | make a domain-specific language (or DSL) to capture the "ideas"
-- | of the language, which we can then use to talk about its content.

-- | In this little snippet, we'll build a JSON DSL, transform it into
-- | a recursive structure, and then use that result to generate some

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import {
  always,
  equals,
  identity,
  ifElse,
  map,
  partial,
} from 'ramda'

const isObject = input => input !== null && typeof input === 'object'

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import { class, interface, implements } from 'sweet-interfaces';

const constant = x => _ => x;
const identity = x => x;
const flip = f => (a, b) -> f(b, c);

interface Setoid {
  // eq :: Setoid a => a ~> a -> Boolean
  eq(b) { return this === b; }
}

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// Sometimes, you might want to supply *some* config, but
// not necessarily *all*. Maybe your password is really
// secret, so you don't want to risk saving it in a config
// file. In which case, you'll want to ask the user to enter
// it when your script runs.

// This interface provides a flexible approach, where
// the user is prompted for a missing key when it's
// requested - if a particular key isn't needed for a given
// run, the user won't need to enter it. Of course, if the

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    var byMonth = R.groupBy(R.prop('Month'));
    var byAuthor = R.groupBy(R.prop('Author'));

    var royalty_key = 'Royalty (SUM)';

    var months_keys = R.uniq(R.map(R.prop('Month'), data)).sort();
    var monthly_revenue =
        R.map((group) => 
            R.reduce((acc, record) => acc + parseMoney(record[royalty_key]), 0, group),
        byMonth(data));

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CATEGORY THEORY FOR PROGRAMMERS

Category Theory 1.1: Motivation and Philosophy 
https://www.youtube.com/watch?v=I8LbkfSSR58&index=1&list=PLbgaMIhjbmEnaH_LTkxLI7FMa2HsnawM_

Composability, Abstraction, Reusability

Category Theory is a higher-level language.
Not a practical, executable language.

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100+ different js counter apps...

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const reg = new RegExp("([^?=&]+)(=([^&]*))?", "g")

function qs (uri) {
  const obj = {}
  uri = uri.replace(/^.*\?/, '')
  uri.replace(reg, map)
  return obj

  function map (a0, a1, a2, a3) {
    obj[decodeURIComponent(a1)] = decodeURIComponent(a3)

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type Request<'i,'o,'k> = 'i * ('o -> 'k)
let bindRequest bind f (s,k) = s, fun v -> bind(k v,f)

type Id = int
type Entity<'e> = Entity of Id option * 'e 
[<Measure>] type money
type User = {name : string; email : string; ballance : int<money>}
type Product = { name : string; quantity : int; price : int<money>}

type Email = {body:string; subject : string}