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FWIW: I'm not the author of the content presented here (which is an outline from Edmond Lau's book). I've just copy-pasted it from somewhere over the Internet, but I cannot remember what exactly the original source is. I was also not able to find the author's name, so I cannot give him/her the proper credits.

Effective Engineer - Notes

What's an Effective Engineer?

cb372 /
Last active Mar 15, 2021
Category theory jargon cheat sheet

Category theory jargon cheat sheet

A primer/refresher on the category theory concepts that most commonly crop up in conversations about Scala or FP. (Because it's embarassing when I forget this stuff!)

I'll be assuming Scalaz imports in code samples, and some of the code may be pseudo-Scala.


A functor is something that supports map.

seansawyer /
Last active May 3, 2020
Managing OpenStack instances with Ansible through an SSH bastion host

Managing OpenStack instances with Ansible through an SSH bastion host

I'm be using DreamCompute as my OpenStack provider, but there are dozens to choose from. I assume you already have Ansible and the OpenStack CLI tools installed.


With the proliferation of OpenStack public clouds offering free and intro tiers, it's becoming very easy to effectively run a simple application for free or nearly free. Also with the emergence of Ansible, you don't need to learn and deploy complicated tools to do configuration management.

# xcode command tool
xcode-select --install
# check
xcode-select -p
# homebrew
/bin/bash -c "$(curl -fsSL"
View SecurePasswordHashing.scala
import java.nio.charset.StandardCharsets._
import javax.crypto._
import javax.crypto.spec._
import base64.Encode.{ apply => toBase64 }
import base64.Encode.{ urlSafe => toBase64UrlSafe }
import base64.Decode.{ apply => fromBase64 }
import base64.Decode.{ urlSafe => fromBase64UrlSafe }