Savelenko

namespace PhantomTypes

module Phantom =

    // Private, so must use function 'prove'.
    type ProofOf<'a> = private | ProofOfA

    // A module proves that it can construct values of type 'a' by providing a value to this function.
    let prove (_ : 'a) : ProofOf<'a> = ProofOfA

Savelenko

module GADTMotivation

(*
Here is a simple motivational example for GADTs and their usefulness for library design and domain modeling. Suppose we
need to work with settings which can be displayed and adjusted in a GUI. The set of possible setting "types" is fixed
and known in advance: integers, strings and booleans (check-boxes).
The GUI should show an example value for each possible setting type, e.g. 1337 for an integer setting and "Hello" for a
string setting. How can we model this small domain of setting types and computing example values?
*)

dsyme

Quick notes on a rant

Some examples related to my tweet rant https://twitter.com/dsymetweets/status/1294276915260522496

1. Implicitly discarding information is so 20th Century

In project programming this hit me this week with a bug:

akhansari

// ========= Event Sourcing in a nutshell

(*
    FriendlyName: string
        Aggregate friendly name.

    Initial: 'State
        Initial (empty) state we will start with.

    Decide: 'Command -> 'State -> 'Event list

JordanMarr

module DragDropPage

open Feliz
open Fable.React
open Fable.React.Props
open ReactDND

type Language = {
    Name: string
}

swlaschin

Architecture

• Use Onion architecture

  • Dependencies go inwards. That is, the Core domain doesn't know about outside layers

• Use pipeline model to implement workflows/use-cases/stories

  • Business logic makes decisions
  • IO does storage with minimal logic
  • Keep Business logic and IO separate

• Keep IO at edges

adymitruk

using System;
using System.Collections.Generic;
using System.Configuration;
using System.IO;
using System.Text;
using System.Threading;
using System.Xml;
using System.Xml.Serialization;
using System.Linq;
using domain;

chrishorton

HANGMANPICS = ['''
  +---+
  |   |
      |
      |
      |
      |
=========''', '''
  +---+

anubhavshrimal

[
{
"name": "Afghanistan",
"dial_code": "+93",
"code": "AF"
},
{
"name": "Aland Islands",
"dial_code": "+358",
"code": "AX"

jwosty

open System
open System.IO

type State<'s, 'a> = State of ('s -> ('a * 's))

module State =
    let inline run state x = let (State(f)) = x in f state
    let get = State(fun s -> s, s)
    let put newState = State(fun _ -> (), newState)
    let map f s = State(fun (state: 's) ->