Paul-Jean Letourneau paul-jean

This is an example of not being precise enough when checking for a value in an object. I inadvertently caused this bug during a live coding exercise in a job interview, and spent a couple minutes debugging before I found it.

The exercise was to code up the Fibonnaci sequence, and I was doing a variation where I memoized previously computed values of the sequence (dynamic programming). I had set up an object to hold values of the sequence as key-value pairs, where the key is n and the value is f(n).

I called the object fibMemo, and initialized it with the first two entries in the

	// Referencing the same object on A.X and B.X, means changing A.X also changes B.X:

	var A = {}, B = {};
	var commonChild = {a:'sameValue'};
	A.X = commonChild;
	B.X = commonChild;
	A.X.b = 'alsoSameValue';
	A.X.b === B.X.b // true

	// Referencing different objects on A.X and B.X, means changing A.X does NOT change B.X:

	public class Factorial {

	public static long fact(long n) {
	if (n == 0) return 1;
	return n * fact(n - 1);
	}

	public static long factTail(long n, long acc) {
	if (n == 1) return acc;
	return factTail(n - 1, n * acc);

	var g = 5;
	console.log("Global value of g = " + g); // g: 5
	var x = function() {
	g = 10;
	};
	var y = new x();
	console.log("After y = new x(), g = " + g); // g: 10
	console.log("After y = new x(), y.g = " + y.g); // y.g: undefined
	// ^^^ because x is referring to global g

	package uk.ac.ucl.cs.GI15.timNancyKawal {
	class Trie[V](key: Option[Char]) {

	def this() {
	this(None);
	}

	import scala.collection.Seq
	import scala.collection.immutable.TreeMap
	import scala.collection.immutable.WrappedString

	Options[f]={a->1,b->2}
	f[x_,opts:OptionsPattern[]]:={x+1,OptionValue[a],OptionValue[b]}
	f[s_String,opts:OptionsPattern[Join[Options@f,{c->"c"}]]]:={s,OptionValue[a],OptionValue[b],OptionValue[c]}

	#!/bin/sh
	cd /Users/rule146/Library/Mail/V2/IMAP-paul.jean.letourneau@imap.gmail.com/[Gmail].mbox/All\ Mail.mbox/A2AE7A8A-125F-45FA-A000-DDD9372AE843/Data/Messages
	grep -E -H "To: hackerschool-w2014@googlegroups.com" *.emlx \| grep -o -E "\\d+.emlx" \| xargs -I % grep -o -E "(\\s\|\()@[a-zA-z0-9]+" % \| tr "(" " " \| sort \| uniq