Jens K. sectore

Async Operations with `useReducer` Hook

9 March, 2019

We were discussing with @erusev what we can do with async operation when using useReducer() in our application. Our app is simple and we don't want to use a state management library. All our requirements are satisfied with using one root useReducer(). The problem we are facing and don't know how to solve is async operations.

In a discussion with Dan Abramov he recommends Solution 3 but points out that things are fresh with hooks and there could be better ways of handling the problem.

Problem

Generating collections of random numbers in PureScript

A problem that I've seen beginners run into in Haskell or PureScript a couple of times now is how to generate a List of random numbers. It's a common requirement for little games (which make for great first projects) to generate these, and it definitely seems to be a stumbling block.

Why are random numbers hard?

Randomness is considered a side effect in purely functional languages, which means that to generate them you usually need access to Eff/IO, which in turn means we need to deal with Monads. And while generating a single random number is usually pretty easy with do-notation, the typical intuition beginners have built when going from single values to a collection is to use map, but that fails.

Type-Directed-Search to the rescue

Kinds

In PureScript there are types of different kinds. Kinds are types for types. For example Int has kind Type, and we write it as Int :: Type. You can ask for the kind of a type in purs psci

> :k Int
Type

Type constructors take types to other types. For example Array (which still needs another type to form a type a value could have, like Array Int):

Why this document?

I upgraded my iPhone 5s to iOS 10 and could no longer retrieve photos from it. This was unacceptable for me so I worked at achieving retrieving my photos. This document is my story (on Ubuntu 16.04).

The solution is to compile libimobiledevice and ifuse from source.

Audience

Who is this guide intended for?

	import PropTypes from 'prop-types';

	type Omit<T, K> = Pick<T, Exclude<keyof T, K>>;

	type Defined<T> = T extends undefined ? never : T;

	/**
	* Get the type that represents the props with the defaultProps included.
	*
	* Alternatively, we could have done something like this:

	#!/usr/bin/env bash
	# https://developers.supportbee.com/blog/setting-up-cucumber-to-run-with-Chrome-on-Linux/
	# https://gist.github.com/curtismcmullan/7be1a8c1c841a9d8db2c
	# https://stackoverflow.com/questions/10792403/how-do-i-get-chrome-working-with-selenium-using-php-webdriver
	# https://stackoverflow.com/questions/26133486/how-to-specify-binary-path-for-remote-chromedriver-in-codeception
	# https://stackoverflow.com/questions/40262682/how-to-run-selenium-3-x-with-chrome-driver-through-terminal
	# https://askubuntu.com/questions/760085/how-do-you-install-google-chrome-on-ubuntu-16-04

	# Versions
	CHROME_DRIVER_VERSION=`curl -sS https://chromedriver.storage.googleapis.com/LATEST_RELEASE`

	import Html exposing (text)



	type alias T = {name: String}
	type alias R b = {b \| name: String, age: Float}
	type alias S a = {a \| name: String}
	type alias Q = {age: Float}

	// the reasonable option

	::shadow .haskell .entity .module,
	::shadow .haskell .identifier .module {
	opacity: 0.5;
	}

	// the nuclear option

	::shadow .line:not(.cursor-line) .haskell .entity .module,