Emil Ong emilong

Undo/Redo is one of those features of an application that you almost always need to have if you are building serious GUI tools for people to do work.

The best way to look at undo/redo is two stacks of operations the user has performed:

The Undo stack is the "history" of what they've done
The redo stack is the breadcrumbs back to the initial state before they started undoing

Some possibly surprising things about Ruby hashes

Ruby hashes can have keys of any type, but Strings and Symbols are the most common.

For symbol keys there is a special syntax (similar to Javascript's object literal syntax).

{ "this is a string key" =&gt; 3 }

	#!/bin/bash

	# Log and graph peformance metrics on a single process
	# Based on: http://brunogirin.blogspot.com.au/2010/09/memory-usage-graphs-with-ps-and-gnuplot.html
	#
	# Requires gnuplot to be installed and on your path.
	#
	# Run: ./process_graph [process name] [pid]

	DEFAULT_PROCNAME="Xorg"

	--- PSQL queries which also duplicated from https://github.com/anvk/AwesomePSQLList/blob/master/README.md
	--- some of them taken from https://www.slideshare.net/alexeylesovsky/deep-dive-into-postgresql-statistics-54594192

	-- I'm not an expert in PSQL. Just a developer who is trying to accumulate useful stat queries which could potentially explain problems in your Postgres DB.

	------------
	-- Basics --
	------------

	-- Get indexes of tables

	sudo apt-get update
	sudo apt-get -y install \
	apt-transport-https \
	ca-certificates \
	curl \
	gnupg-agent \
	software-properties-common
	curl -fsSL https://download.docker.com/linux/ubuntu/gpg \| sudo apt-key add -
	sudo add-apt-repository \
	"deb [arch=amd64] https://download.docker.com/linux/ubuntu \

	<?xml version="1.0" encoding="UTF-8"?>
	<!-- Generated by FME 2017.1.2.0 (Build 17722) -->
	<kml xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:gx="http://www.google.com/kml/ext/2.2" xmlns:atom="http://www.w3.org/2005/Atom" xmlns="http://www.opengis.net/kml/2.2">
	<Document><LookAt>
	<longitude>-102</longitude>
	<latitude>38.5</latitude>
	<range>7000000</range>
	<tilt>10</tilt>
	<heading>0</heading>
	</LookAt>

	#!/bin/bash
	# Add to instance metadata with `gcloud compute instances add-metadata \
	# instance-name --metadata-from-file startup-script=idle-shutdown.sh` and reboot
	# NOTE: requires `bc`, eg, sudo apt-get install bc
	# Modified from https://stackoverflow.com/questions/30556920/how-can-i-automatically-kill-idle-gce-instances-based-on-cpu-usage
	threshold=0.1

	count=0
	wait_minutes=60
	while true

	require "yaml"
	require "json"

	puts YAML.dump(JSON.load(YAML.load_file(ARGV.first).to_json))