\lambda

Just a bunch of links:

• Thoughts about Haskell, Scala, Clojure, Erlang
• Yet another Haskell vs. Scala question

The Full-Stack Programmer

Old idea formalized in a catchy new term: read more about The Full-Stack Programmer.
It will be interesting if this idea gains traction.

An algorithm for finding cut vertices

Related Readings: Biconnected Component
Note: kind of similar to finding strongly connected components

Special thanks to JJ & Brent for this!

Maximum subarray problem

This is one of those nice little problems that I used to know how to solve, but I have forgotten over time...

Problem Description: Given a array of n integers, (there can be negative integers), find the subarray which gives you the maximum sum in O(n) time.

Solution (Intuition): Observe that the smallest max sum is 0 (the solution subarray can be empty). Hence, we do not want to go below this number. A positive number contributes to increasing sum (so we take it in), but negative numbers decrease the sum. Hence, the solution subarray must start with a positive number. We have two variables, max_so_far and max_ending_here.

Solution (Code):

Buzzword: NoSQL

select fun, profit from real_world where relational=false;

Design Patterns

High-level ideas:
- Lazy initialization
- Singleton/Multiton
- Proxy/Facade
- Decorator
- Factory
- Observer
- Publisher/Subscriber

HipHop for PHP

HipHop for PHP transforms PHP source code into highly optimized C++. It was developed by Facebook and was released as open source in early 2010.

See this Facebook post and GitHub (source)

Gearman

Gearman provides a generic application framework to farm out work to other machines or processes that are better suited to do the work. It allows you to do work in parallel, to load balance processing, and to call functions between languages.

See Gearman.org

stdClass in PHP

stdClass is instead just a generic 'empty' class that's used when casting other types to objects. I don't believe there's a concept of a base object in PHP

For the record... courtesy of stackoverflow.com
Further reading: here and here.

COW in PHP

Copy-on-write (sometimes referred to as "COW") is an optimization strategy used in computer programming. The fundamental idea is that if multiple callers ask for resources which are initially indistinguishable, they can all be given pointers to the same resource. This function can be maintained until a caller tries to modify its "copy" of the resource, at which point a true private copy is created to prevent the changes becoming visible to everyone else. All of this happens transparently to the callers. The primary advantage is that if a caller never makes any modifications, no private copy need ever be created.

Recently, I was dealing with large data sets in PHP and I was wondering how PHP's garbage collection works. I discovered that PHP actually uses copy-on write (COW)!

Consider the following script, which demonstrates how PHP's GC works.
Note that before PHP 5.3.0, circular memory references result in memory leaks.

Zarro Boogs

By design, Bugzilla is programmed to return the string "zarro boogs found" instead of "0 bugs found" when a search for bugs returns no results. "Zarro Boogs" is a facetious meta-statement about the nature of software debugging. Bug tracking systems like Bugzilla readily describe how many known bugs are outstanding. The response "zarro boogs", is intended as a buggy statement itself (a misspelling of "zero bugs"), implying that even when no bugs have been identified, software is still likely to contain bugs that haven't yet been identified.

Source: http://en.wikipedia.org/wiki/Bugzilla#Zarro_Boogs

@Override in Java

@Override

Indicates that a method declaration is intended to override a method declaration in a superclass. If a method is annotated with this annotation type but does not override a superclass method, compilers are required to generate an error message.

Tip of the day: The @Override annotation is a useful feature to ensure that you are overriding the correct method. Mostly used in places such as:

@Override
public int hashCode()

@Override
public boolean equals(Object obj)

Heisenbug, Bohrbug, Mandelbug, Schroedinbug

You may have heard of the Heisenberg uncertainty principle, the Bohr model for an atom or even ways to catch Schrödinger's cat. However, its unlikely that you have heard of the Heisenbug, Bohrbug, Schroedinbugs or Mandelbugs. For the geek, these funny names are actually unusual software bugs!

Heisenbug
The name may seem to rhyme well with Heisenberg, but the Heisenbug is actually "a bug that disappears or alters its behavior when one attempts to probe or isolate it." The Freenet Project describes a Heisenbug in certain Java virtual machines.

Bohrbug
The Bohrbug is a sort of antonym of the Heisenbug, as this bug does not disappear or alter its characteristics when it is researched.

Mandelbug
The Mandelbug, named after Benoit Mandelbrot (think Mandelbrot set), is a bug whose underlying causes are so complex and obscure as to make its behavior appear chaotic.

Schroedinbug
The Schroedinbug is a design or implementation bug in a program that doesn't manifest until someone reading source or using the program in an unusual way notices that it never should have worked, at which point the program promptly stops working for everybody until fixed. Here, an Office developer describes "stupid SQL tricks" to get rid of a "classic Schroedinbug."