Renzo Canepa rcanepa

Rich Already Answered That!

A list of commonly asked questions, design decisions, reasons why Clojure is the way it is as they were answered directly by Rich (even when from many years ago, those answers are pretty much valid today!). Feel free to point friends and colleagues here next time they ask (again). Answers are pasted verbatim (I've made small adjustments for readibility, but never changed a sentence) from mailing lists, articles, chats.

How to use:

The link in the table of content jumps at the copy of the answer on this page.
The link on the answer itself points back at the original post.

Table of Content

FWIW: I (@rondy) am not the creator of the content shared here, which is an excerpt from Edmond Lau's book. I simply copied and pasted it from another location and saved it as a personal note, before it gained popularity on news.ycombinator.com. Unfortunately, I cannot recall the exact origin of the original source, nor was I able to find the author's name, so I am can't provide the appropriate credits.

Effective Engineer - Notes

By Edmond Lau
Highly Recommended 👍
http://www.theeffectiveengineer.com/

What's an Effective Engineer?

Condition Systems in an Exceptional Language by Chris Houser

I recently watched Chris Houser's talk from Clojure/conj 2015 on condition systems in Clojure. I enjoyed the subject, so I decided to write up the talk as a way of encouraging me to really understand it, and in the hope that it might help others understand it.

The last time I heard about Common Lisp's condition system was at a talk by Didier Verna at ACCU in Bristol in 2013 (slides here). It sounded really interesting, but I didn't understand it well enough.

tl;dr

Chris Houser talks about different ways of handling errors in Clojure. Based on examples from Peter Seibel's book, Practical Common Lisp, he describes condition systems, which are also known as resumable exceptions, or restarts.

What is this?

Following this guide will set up a local Elasticsearch with Kibana and Marvel using Homebrew and Homebrew Cask

Prerequisites

If you already have Java installed on your system, skip steps Install Cask and Install Java

If you already have Java and Homebrew installed on your system, skip steps Prerequisites, start at Install Elasticsearch and Kibana after running $ brew update

Install Homebrew

$ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

(:identity req) is auth backend independent way to access user data
login and logout implementation depends on auth backend
:current-user doesn't imply that authentication is required, route should also have :auth-rules if authentication is required

Things that programmers don't know but should

(A book that I might eventually write!)

Gary Bernhardt

I imagine each of these chapters being about 2,000 words, making the whole book about the size of a small novel. For comparison, articles in large papers like the New York Times average about 1,200 words. Each topic gets whatever level of detail I can fit into that space. For simple topics, that's a lot of space: I can probably walk through a very basic, but working, implementation of the IP protocol.

	/*
	* Handling Errors using async/await
	* Has to be used inside an async function
	*/
	try {
	const response = await axios.get('https://your.site/api/v1/bla/ble/bli');
	// Success 🎉
	console.log(response);
	} catch (error) {
	// Error 😨

	%253Cscript%253Ealert('XSS')%253C%252Fscript%253E
	<IMG SRC=x onload="alert(String.fromCharCode(88,83,83))">
	<IMG SRC=x onafterprint="alert(String.fromCharCode(88,83,83))">
	<IMG SRC=x onbeforeprint="alert(String.fromCharCode(88,83,83))">
	<IMG SRC=x onbeforeunload="alert(String.fromCharCode(88,83,83))">
	<IMG SRC=x onerror="alert(String.fromCharCode(88,83,83))">
	<IMG SRC=x onhashchange="alert(String.fromCharCode(88,83,83))">
	<IMG SRC=x onload="alert(String.fromCharCode(88,83,83))">
	<IMG SRC=x onmessage="alert(String.fromCharCode(88,83,83))">
	<IMG SRC=x ononline="alert(String.fromCharCode(88,83,83))">

	/**
	* Think of this "main.js" file as your application bootstrap.
	*/

	import Vue from 'vue'
	import Resource from 'vue-resource'
	import VueRouter from 'vue-router'
	import routes from './routes'
	import middleware from './middleware'

	(ns background
	(:require [clojure.tools.logging :as log])
	(:import [java.util.concurrent]))

	(defonce !executor (delay (java.util.concurrent.Executors/newCachedThreadPool)))

	(defn background
	"Calls the fn passed in a thread from a thread pool, returning immediately.
	Unlike future, background does not swallow exceptions."
	[f]