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Command Line Navigation Cheat Sheet

Alt key may need to be Esc on macOS depending on your terminal settings.

Cursor Movement

Shortcut	Action
Ctrl+A	Move to beginning of line
Ctrl+E	Move to end of line

dra1n

What is dhall?

• Dhall is a programmable configuration language that you can think of as: JSON + functions + types + imports

Functions

• Built-in
• User defined

let makeUser = \(user : Text) ->
      let home       = "/home/${user}"
 let privateKey = "${home}/.ssh/id_ed25519"

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const range = (start: number, end: number) =>
  Array.from({ length: end - start + 1 }, (v, k) => k + start);

/* Monad */
const ret = <T>(x: T): T[] => [x];
const bind = <T>(xs: T[], f: (v: T) => T[]): T[] => xs.map(f).flat();
const fail = <T>(_: T): T[] => [];

/* Knight problem */
type KnightPos = [number, number];

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// user module
const receive = (_user, sender, message) => {
  console.log(`${new Date().toLocaleString()} [${sender}]: ${message}`);
};

// chat room module
const createChatRoom = (users = []) => ({
  users
});

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class ChatRoom {
  constructor(users = []) {
    this.users = users;
  }

  addUser(user) {
    this.users.push(user);
  }

  sendMessage(user, message) {

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const execute = (command, ...args) => command(...args);

function PlaceOrderCommand(order, id) {
  return orders => {
    const result = [...orders, { id }];
    console.log(`You have successfully ordered ${order} (${id})`);

    return { success: true, result };
  };
}

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(ns number-puzzles.imbaru
  (:refer-clojure :exclude [==]) ;; Prevent ns conflict
  (:require [clojure.core.logic :refer :all]))

(def answers (run* [q]
                   (fresh [r1 r2 r3 r4
                           r5 r6 r7 r8
                           r9 r10 r11 r12
                           r13 r14 r15 r16]

dra1n

Teaching New Toys Old Tricks

What's in the toolbox?

• createSlice
• createAction
• createAsyncThunk
• configureStore

What's the slice?

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Where we left

• UI should be an afterthought
• Write code that allows to sepearate business logic frow UI.
• Write code that allows to inject any hard-to-test, too-verbose, want-this-mocked stuff logic.

Is redux a good tool for impelmenting these ideas?

• It has special place for handling business logic, called middleware.
• Popular middleware have a mechanism for context injection. If you are writing your own custom middleware, then you probably should think about adding this too.

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UI should be an afterthought

What this logic separation gives?

• Better testability via the fewer levels of indirection. To trigger business processes you call methods or invoke functions, not clicking buttons.
• Better testability via DI in some form. In React code jest.mock is the only "unobtrusive" way to replace dependencies.
• Discoverability. Business logic isn't scattered across a bunch of components.
• Reusability. Sometimes you want to reuse only business logic and not the UI tied to it.
• Readability. It is easier to reason about business logic.