Aaron Dai mrvicadai

Algebraic Effects in JavaScript part 1 - continuations and control transfer

This is the first post of a series about Algebraic Effects and Handlers.

There are 2 ways to approach this topic:

Denotational: explain Algebraic Effects in terms of their meaning in mathematics/Category theory
Operational: explain the mechanic of Algebraic Effects by showing how they operate under a chosen runtime environment

Both approaches are valuables and give different insights on the topic. However, not everyone (including me), has the prerequisites to grasp the concepts of Category theory and Abstract Algebra. On the other hand, the operational approach is accessible to a much wider audience of programmers even if it doesn't provide the full picture.

Ecrypt data using aes-256-cbc without salt

$ echo  'this is hello world'  | openssl  aes-256-cbc -a -nosalt -k hello
HEQ/s/mOMof648tJxJvvwtHUTcq2j021RbgvqLA02lY=
-a means encoding the output using base64
-nosalt force openssl do encryption without salt
-k the encryption key

Phantom types in ReasonML

Introduction

"A phantom type is a parametrised type whose parameters do not all appear on the right-hand side of its definition..." Haskell Wiki, PhantomType

The following write-up is intended as an introduction into using phantom types in ReasonML.

Taking a look at the above definition from the Haskell wiki, it states that phantom types are parametrised types where not all parameters appear on the right-hand side. Let's try to see if we can implement a similar example as in said wiki.

The repository for the assignment is public and Github does not allow the creation of private forks for public repositories.

The correct way of creating a private frok by duplicating the repo is documented here.

For this assignment the commands are:

Create a bare clone of the repository. (This is temporary and will be removed so just do it wherever.)

git clone --bare git@github.com:usi-systems/easytrace.git

When receiving JSON data from other resources(server API etc), we need Json.Decode to convert the JSON values into Elm values. This gist let you quickly learn how to do that.

I like to follow working example code so this is how the boilerplate will look like:

import Graphics.Element exposing (Element, show)
import Task exposing (Task, andThen)
import Json.Decode exposing (Decoder, int, string, object3, (:=))

import Http

Should be work with 0.18

Destructuring(or pattern matching) is a way used to extract data from a data structure(tuple, list, record) that mirros the construction. Compare to other languages, Elm support much less destructuring but let's see what it got !

Tuple

myTuple = ("A", "B", "C")
myNestedTuple = ("A", "B", "C", ("X", "Y", "Z"))

npm v3.10 - ◾

⚠️ This gist is outdated, but most of the commands are still relevant. ⚠️

Update npm itself

npm install -g npm
# Downgrade to a specific version
npm install -g npm@6

npm rank

This gist is updated daily via cron job and lists stats for npm packages:

Top 1,000 most depended-upon packages
Top 1,000 packages with largest number of dependencies
Top 1,000 packages with highest PageRank score

	module FileUtils exposing (..)

	import Native.FileUtils
	import Html exposing (..)
	import Html.Events exposing (..)
	import Http exposing (Body)
	import Json.Decode as Json


	type alias File =

	// imports a couple of java tasks
	apply plugin: "java"

	// List available tasks in the shell
	> gradle tasks

	// A Closure that configures the sourceSets Task
	// Sets the main folder as Source folder (where the compiler is looking up the .java files)
	sourceSets {
	main.java.srcDir "src/main"