jfarmer

true and false vs. "truthy" and "falsey" (or "falsy") in Ruby, Python, and JavaScript

Many programming languages, including Ruby, have native boolean (true and false) data types. In Ruby they're called true and false. In Python, for example, they're written as True and False. But oftentimes we want to use a non-boolean value (integers, strings, arrays, etc.) in a boolean context (if statement, &&, ||, etc.).

This outlines how this works in Ruby, with some basic examples from Python and JavaScript, too. The idea is much more general than any of these specific languages, though. It's really a question of how the people designing a programming language wants booleans and conditionals to work.

If you want to use or share this material, please see the license file, below.

Update

Kerrick

# Download Sublime Text 2 from http://www.sublimetext.com/2
# If you aren't root, sudo su

tar -xvjf Sublime\ Text\ 2*.tar.bz2
mv Sublime\ Text\ 2/ /opt/sublime-text-2/
ln -s /opt/sublime-text-2 /usr/local/sublime-text-2
ln -s /usr/local/sublime-text-2/sublime_text /usr/local/bin/sublime_text
rm Sublime\ Text\ 2*.tar.bz2 

# Sublime Text 2 can now be run as normal user with command "sublime_text"

jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

MohamedAlaa

tmux shortcuts & cheatsheet

start new:

tmux

start new with session name:

tmux new -s myname

avit

# Regex with two named captures both named "word"
r = %r{
  (?<word>[a-z]+)\s+
  (?<word>[a-z]+)
}xi

m = r.match("one two")
# => #<MatchData "one two" word:"one" word:"two">

m.captures

andkerosine

$stack, $draws = [], {}

def method_missing *args
  return if args[0][/^to_/]
  $stack << args.map { |a| a or $stack.pop }
  $draws[$stack.pop(2)[0][0]] = args[1] if args[0] == :<
end

class Array
  def +@

simonewebdesign

<button id="btn">Click me!</button>

<script>

var btn = document.getElementById('btn');

btn.onclick = function() { 
  // will be overwritten! 
  console.log('[onclick] foo'); 
}

lavoiesl

#!/bin/bash
# Converts an image in a multi-resolution favicon
# Requires Imagemagick
# @link https://gist.github.com/lavoiesl/4113857

if [[ "$#" != "2" ]]; then
    echo "Usage: $0 input.png output.ico" >&2
    exit 1
fi

simonewebdesign

#!/bin/bash

# loop through parameters
for WORD; do
  echo $WORD
done

# another way is:
for i in "$@"
do