How to tell you’re a bad programmer

How to tell you’re a bad programmer:

1. You think you’re an awesome programmer.

2. But no one else has ever told you so.

3. You’ve never looked at old code you wrote and thought, “Ewwww! That is horrible code! What was I thinking???”

4. You’ve never looked at someone else’s code and thought, “Dang, whoever wrote this is a freaking genius.”

Note that this also works if you substitute <other profession> for “programmer,” and <output of other profession> for “code.”

If you don’t see growth, it probably ain’t happening.  If you don’t see growth potential, it probably ain’t happening either.

Using Stack Overflow

Joel Spolsky and Jeff Atwood are starting a new website called Stack Overflow, it’s going to be a free programming Q&A website.

I’m a fan of both of those guys (I even have an autographed copy of Joel’s book!), so I signed up to be a beta user to see how it develops. I was trying to come up with a good way to give Stack Overflow a test drive, and I think I’ve hit on something: use it to build a web 2.0-ish site. I’ve been wanting to build a site for myself for at least the last year – I can picture it in my head (and on paper), what it should do and what the user interaction should look like, but I haven’t spent any time actually figuring out how to build the darn thing.

You see, I’m comfortable in C/C++/Perl/Python/x86 assembly (really), but I’ve never done any database or web-y development. Enter Stack Overflow – hopefully it will be a good place to learn about web programming.

I’ll update this blog with my progress once Stack Overflow goes live, wish me luck.

And Jeff: Give me a call when you decide to learn C, I taught it at Purdue for a few years back in grad school and really enjoyed teaching it – maybe you could trade me some .NET lessons for some C lessons. You check my post on pointers to get started. :-)

Data is more agile than code

Peter Norvig talks about the need for a startup company to go fast – and also in the right direction – at his Startup School 2008 talk.

“Sure you gotta go fast, but if you’re not getting feedback to figure out if you’re going in the right direction it doesn’t matter how fast you go.” (2:47 in the video.)

That advice can apply to both technology and the business sides of a company, but here Norvig focuses on the feedback necessary to make sure the technology you’re developing succeeds.

He suggests you can get this vital feedback by:

“Acquiring lots of data [and] running machine learning over it… The key here is that no matter how agile you are as coders, and I understand that you’re all great, data is going to be more agile than code. Because you’ve got to right the code yourself, but the data you can leverage… there’s an immense multiplying factor that way.”

I guess this Lisp/AI guru from Google knows a thing or two about using lots of data, eh?

He goes on to describe how Google has used machine learning over large data sets for their image search, text segmentation and Google Sets. It’s a great talk, I highly recommend it.

I like the idea of letting the data and algorithms do as much of the heavy lifting as possible – the knowledge I want to share with my users may already be in the data, I’ve just got to dig it out!

Knuth hates XP

In this recent interview, Donald Knuth says:

“Still, I hate to duck your questions even though I also hate to offend other people’s sensibilities—given that software methodology has always been akin to religion. With the caveat that there’s no reason anybody should care about the opinions of a computer scientist/mathematician like me regarding software development, let me just say that almost everything I’ve ever heard associated with the term “extreme programming” sounds like exactly the wrong way to go…with one exception. The exception is the idea of working in teams and reading each other’s code. That idea is crucial, and it might even mask out all the terrible aspects of extreme programming that alarm me.

I also must confess to a strong bias against the fashion for reusable code. To me, “re-editable code” is much, much better than an untouchable black box or toolkit. I could go on and on about this. If you’re totally convinced that reusable code is wonderful, I probably won’t be able to sway you anyway, but you’ll never convince me that reusable code isn’t mostly a menace.”

There are only a few people who can get away with saying that and actually have people listen to them – and Knuth is definitely one of them. I would love to hear him expand on the “terrible aspects of extreme programming.” If he had an email address I would ask him about it, but unfortunately he doesn’t.

Understanding C pointers: Part 1

As I said in “Understanding C pointers: Part 0,” I’m going to try to explain how C pointers work.

Let’s start with the basics. Here’s some simple C code:

  int x = 23;
  int y = x;

You can think of each variable as a box which holds the value of that variable. So in this example we have 2 boxes, named “x” and “y”. After these two statements execute the “x” box contains 23, and the “y” box also contains 23. The picture looks like this:

Pretty straightforward stuff. If we add this code:

  x = 17;

the pictures changes to look like this:

Nothing too fancy there.

Next example: let’s add a pointer into the mix.

  int x = 23;
  int y = x;
  int * p = & x;

If the * or & in the above code scare you, please take a deep breath and relax. We’ll get through this, I promise. :-)

“x” is a variable of type integer. So is “y”. The “int *” before p means that p is a variable of type “pointer to integer” otherwise known as an “integer pointer.” Nothing magical there. The “&” before “x” can be read as the “address of x,” or “the box named x.” Which means the pointer “p” points to the box named “x”.

As in the previous examples we have a box named “x” and another box named “y”. This example adds a pointer to an integer called “p”. You can think of this pointer as simply another box, named “p”. The value in the “p” box is a pointer to another box. For the boxes “x” and “y” we can say things like “x holds the number 23,” but for the box “p” we say “p holds a pointer to the box named “x”".

A picture is worth at least a few words:

Watch what happens when we add this next line to the example:

  *p = 17;

The * before the “p” tells us we’re changing the value of what “p” points to. We are not changing the value of “p” itself. The number 17 gets put wherever the value of the “p” box point to – which is the “x” box in this case. After this code runs our picture looks like this:

Notice that “p” has not changed. “p” still points to box “x”. Only the value in the box that “p” was pointing to changed.

Let’s add a couple more lines to that example:

   p = & y;
  *p = 42;

The first line changes the value in the box “p” to be a pointer to the box “y”. The 2nd line changes the value in the box that “p” points to be 42. The result looks like this:

Drawing these pictures may seem unnecessary, but I guarantee that drawing them will help you understand your code. Even if you understand pointers completely, when faced with a pointer-laden interview question it’s a good idea to draw your data structures and pointers. This way the interviewer can see how you’re thinking about the question, which is frequently more useful than simply getting the “right” answer.

Okay, that’s the basics. See – pointers aren’t that bad.

And it turns out that the way a computer actually implements variables/pointers is a lot like our simple “boxes” model. Tune in next time for more about that.