Maybe I'm missing something... Why the assumption that all (or even the majority of) HN readers are interested only in developing web apps?

It suffices that just one such individual exists to invalidate the claim of the title.

Quick, someone bring more koolaid!

for a non-php developer that article is kind of trivial entry level stuff so no value either.

I assume the title was targeted at Peteris' normal audience, not web app developers.

From the about: Peteris Krumins’ blog about programming, hacking, software reuse, software ideas, computer security, google and technology.

The purpose of the Hacker News website is to serve past/present/future ycombinator candidates. I'm not even a web app developer, I wrote C code for an $8 processor today.

The title (as submitted by the author of the blog) says "Absolutely Must Know," which is quite hyperbolic.

I would suggest: Basic tricks of bit manipulation.

Consider that this topic is covered in K. N. King's book C Programming: A Modern Approach, in Chapter 20: Low-Level Programming, on page 451

not all of us here are (purely/originally) web app developers.

Yes, even for web applications, bitwise manipulation will come in handy at some point.

Personal anecdote: I recently had to combine two arbitrary unsigned 32 bit integers into one unsigned 64 bit integer to make a unique ID for an index. Not sure how I would have done that without bitwise manipulation.

lol.

in python: (2 ^ 32)*upper + lower

edit: dbl star goes blank .. so in almost python

You're XORing 32 into 2, multiplying it by the top word, and adding the bottom word?

Also, you think exponentiation and multiplication is faster than a shift and an OR? I think you're the target audience for this article, and I revise my opinion (thankfully unstated) about whether this is material every developer "must" know.

Surprisingly (I just benchmarked it myself), the times are near the same.

Here's my benchmark (in case I made a mistake):

  import time

  def combine(upper,lower): return (2**32)*upper + lower
  def combine2(upper,lower): return (upper << 32) | lower

  def test_combine():
  	start = time.clock()
	for i in range(10000000):
		combine(i,i)
	end = time.clock()
	output = 'The time taken for combine() is ' + str(end - start)
	print output

  def test_combine2():
	start = time.clock()
	for i in range(10000000):
		combine2(i,i)
	end = time.clock()
	output = 'The time taken for combine() is ' + str(end - start)
	print output

Also see http://wiki.python.org/moin/PythonSpeed/PerformanceTips#Pyth...

That's surprising; it's more than twice as slow in Ruby (yeah, yeah). It's also (for obvious reasons) orders of magnitude faster in C --- if you were crazy enough to actually write code that way.

I don't know much about Python so forgive me if this is stupid - but could 2^32 have been optimized as a constant, so that the result is just a multiplication and an addition?

Okay okay ... I should have written:

import math; math.pow(2,32)

I tried to use the double star operator, but that is markup for italics in this software, so it was edited out.

I considered that solution. And in thinking about why I chose to do bit-shifting, I remembered why: I actually needed to combine two _signed_ 32 bit integers in MySQL, and since I wasn't sure how signed integers are stored in MySQL, I figured that I could just use bit-shifting and move on.

Here's an example where a web developer may find bit=fiddling useful:

- How would you, compactly and discretely, represent in a cookie the days on which a user has visited your site this month?

(I am decided not a web developer, but this is a question I'd ask a web developer on a phone screen were I to hire one).

same here! I was hoping it would just have the title and then be a blank page.