Enrico Polanski enricopolanski

Monoids in Haskell, an Introduction

Why should programmers care about Monoids? Because Monoids are a common pattern that shows up over and over in programming. And when patterns show up, we can abstract them and leverage work we've done in the past. This allows us to quickly develop solutions on top of proven, stable code.

Add Commutative Property to a Monoid (Commutative Monoid) and you have something that can be executed in parallel. With the end of Moore's Law, parallelism is our only hope to increasing processing speeds.

What follows is what I've learned after studying Monoids. It is hardly complete, but hopefully will prove to be helpful as an introduction for others.

Monoid Lineage

Mono Repository Tool Comparison

For Web Client / Front End Projects

(That Probably Use HTML, CSS, and JS)

I made a list of 20 things I might want out of a monorepo tool for a Design System to use as a basis for comparing some of the options including Lerna, Northbrook, and Rush.

⚠️ Northbrook's author says the project is pretty dead and now uses Lerna.

Qualifications Wanted

Git 101, with Exercises

Git is the key tool we use to allow multiple people to work on the same code base. Git takes care of merging everyone's contributions smoothly. Hence, learning how to use Git is critical to contributing to open source.

Exercises

Exercise 1: Go through the Try Git Guide

Exercise 2: Learn How to file a github issue.

Array Iteration

https://gist.github.com/ljharb/58faf1cfcb4e6808f74aae4ef7944cff

While attempting to explain JavaScript's reduce method on arrays, conceptually, I came up with the following - hopefully it's helpful; happy to tweak it if anyone has suggestions.

Intro

JavaScript Arrays have lots of built in methods on their prototype. Some of them mutate - ie, they change the underlying array in-place. Luckily, most of them do not - they instead return an entirely distinct array. Since arrays are conceptually a contiguous list of items, it helps code clarity and maintainability a lot to be able to operate on them in a "functional" way. (I'll also insist on referring to an array as a "list" - although in some languages, List is a native data type, in JS and this post, I'm referring to the concept. Everywhere I use the word "list" you can assume I'm talking about a JS Array) This means, to perform a single operation on the list as a whole ("atomically"), and to return a new list - thus making it mu

How to have specific .gitignore for each git branch

Objective

My objective is to have some production files ignored on specific branches. Git doesn't allow to do it.

Solution

My solution is to make a general .gitignore file and add .gitignore.branch_name files for the branches I want to add specific file exclusion. I'll use post-checkout hook to copy those .gitignore.branch_name in place of .git/info/exclude each time I go to the branch with git checkout branch_name.

	#pragma once

	#define DYN_ARR_OF(type) struct { \
	type *data; \
	type *endptr; \
	uint32_t capacity; \
	}

	#if !defined(__cplusplus)
	#define decltype(x) void*

	import * as t from 'io-ts'
	import * as React from 'react'
	import { render } from 'react-dom'

	type Field = t.StringType \| t.NumberType \| t.BooleanType
	interface Form extends t.InterfaceType<{ [key: string]: Field }> {}

	const toReactElement = (f: Form \| Field): React.ReactElement<any> => {
	// f is a tagged union
	switch (f._tag) {

	var fs = require("fs");
	var path = require("path");
	var cheerio = require("cheerio");

	module.exports = (mypath) => {
	var inputFile = fs.readFileSync(mypath, "utf8");

	var $ = cheerio.load(inputFile, {xmlMode:true});

	// defines the selector

	// __tests__/example.js
	jest.mock('fs');

	it('should serve as a nice example', () => {

	const fs = require('fs')

	// fs can be set up at any point by calling __configureFs.
	fs.__configureFs({
	'/test': {

	<!DOCTYPE html>
	<html>

	<head>
	<title>Sine Wave</title>
	<script type="text/javascript">
	function showAxes(ctx,axes) {
	var width = ctx.canvas.width;
	var height = ctx.canvas.height;
	var xMin = 0;