Last night I was writing some for OS161 – I was implementing a fork(), execv(), getpid(), waitpid() and exit() for the OS161 kernel. I was using Visual Studio Express VC++ edition beta2 to write the code and I had a little ruby script to upload changed file to my linux (gasp!) box and a little script there that would build the kernel whenever the files changed. That way I get to develop code on an OS that has a notion of a unified clipboard and such pleasantries and get to build it wherever the tools are available. I also got a minimal shell like first process done.

Don’t get me wrong when I say this, but I sometimes like to think of myself as a fairly decent imperative programmer – I would be comparably good to many people you might meet. Ever since I came to college functional programming has been rewiring my brain. And its beginning to hurt. And I am enjoying it. And sometimes you need a break.

Hence writing missing pieces in a simplistic os kernel is a nice break. And I am going “Ooh! Look I have variables! Ooh! Look I can reassign the value of this thing. Look, I have loops”. And that’s a nice world to be in, if you can think in terms of state well – for those of you imperative programmers don’t know what that is, it means that things have changable values (like x=5 and x ++;) – and those of you who don’t realize you are imperative programmers, here is a simple test: if you are not a Haskell (and similar) programmer Or Scheme programmer (without set!) Or mathematician Or someone who goes from day to day without anything in the world affecting you, you are a imperative programmer of some device.

So I was enjoying being imperative for a while and then when I had it all going halfway into the night – I had multiple processes forking and execing and waitpiding and exiting – the whole crashes. And then it crashed again. And this was crazy, because all the of the pieces were things I had tested separately and yet they crashed when they came together. Somewhere in the back of my head there was this little elephant called lambda laughing on the floor ignoring his cons-kit for a bit. But wait a minute, I thought all this functional programming was making me a better programmer – I thought I could think more clearly about composition.

After about 2hours of meditation and atleast one or two sets of forays into the debugger as a last recourse, I realized what the problem was that I was not writing things back onto the user space stack in the correct alignment in some cases – and the this was some dword alignment requirement of this machine that was not mentioned anywhere. Lambda and the Turing tape looked down, looking a little sorry. I was in a bad mood by the end of it and that wasn’t fair – that was my little imperative break.

All of this, gets me to some of the conversations with some of my professors here. Dan Friedman is one of the kindest gentlest people you can talk to – and pretty much every other sentence some brain mutilating idea, said in the kindest subtlest way possible. So it happened that I needed to prove that something is not possible (it is related to the hypothetical apply-iterator operator I speak of here). Fifiteen minutes after the conversation I am thinking about higher order programming with continuations and my brain is hurting. (do you know what that means? If you don’t you need to go though the experience of hitting upon an idea that changes the way you look at the world. Changes the way you look at the world does not mean that the next time you eat a burger you look at it slightly more from the left, it is a little more encompassing an idea.)

An idea isn’t responsible for the people who believe in it.

Programming languages are devices to express thought. The fact that you can also create software using them are only secondary to this larger idea. Languages carry ideas of meaning and operation and you can compose these things together to create larger meanings and wider operations, or compose them to narrow down their scope. If you are a starting C programmer or an accomplished C# or Java programmer, it maybe hard to see things this way – but that is ok, you don’t always have to know the full import of what you could be doing. (I will write about Haskell and the wizard called Prof Amr Sabry some other time.)

One of the hardest things or like Prof Friedman says it is probably the simplest of all things is the idea of a continuation. It is an idea so simple that it drives you crazy trying to understand it. Imagine that if you did something, anything, it has rippling effects across the rest of all time – now imagine that you can take this ‘rest of all time’ and assign it to a variable and pass it around through all the operations you do, such that at some time you can go back to that rest of the world. That is a continuation. That as a programming device is good way to inflict some brain damage if you try to internalize it.

That’s about when I thought I should quit. That I probably should not go functional. All of this was too hard – you start out with something because you feel that there is some beauty and some truth in it. And when that fails you, maybe its time to betray you way of thinking – maybe its time to quit. By this point, you realize, that I might be quiet crazy, and that it might be rubbing off on you since you are still reading this. Betray the temple of Lambda?

That’s when Judas’s song from Jesus Christ Super Star (which I have been listening to a lot these days) plays in the back of my mind, when he does to Caiphus to betray Christ -

Now if I help you, it matters that you see

These sordid kinda things are coming hard to me.

It's taken me some time to work out what to do

I weighed the whole thing out before I came to you.

I have no thought at all about my own reward.

I really didn't come here of my own accord.

Just don't say I'm ... damned for all time.

I came because I had to; I'm the one who saw.

Jesus can't control it like he did before.

And furthermore I know that Jesus thinks so too.

Jesus wouldn't mind that I was here with you.

I have no thought at all about my own reward.

I really didn't come here of my own accord.

Just don't say I'm ... damned for all time

- Damned for All time, Judas’s Song, JCSS.

And then something snapped back in place and I was at it again. Why have such a device as continuations? Why bother? Well we understand little of continuations in my opinion. They are a thinking tool for the future. How can something so mind bogglingly hard be useful?

A long time back I remember seeing a beginner book about BASIC programming. That book had an example of the quicksort algorithm in basic written using gotos. It was a only a few lines. I spent a whole evening trying to understand what that was doing. And I didn’t succeed. I could execute the statements in my mind and see how they work, but I could see how such a beast could be created. I couldn’t see the way you would have to think to create something like that. Several years later I saw copper bars by Tylisha C Anderson and it was the same death by gotos. I could not understand it.

Many years ago they got together and killed off gotos and created a new-kid-on-the-block called structured programming. They took gotos and created a set of patterns that are sufficiently expressive to do anything that you could do using gotos. And then they killed off goto. The offspring forms the basis of almost all imperative programming today.

The real value of something powerful that we cannot tame yet is in what you can derive out of it. That’s when you say, in the conventional sense, that something is sufficiently mature – when people who don’t understand the first thing about it can use it to solve their programs (that’s the sense in which I sometimes say that windows is more mature than linux…). I think I should stop now. As you can see, college has been fun so far.

What then to do about this Jesus-mania?

Now how to we deal with a carpenter king?

Where do we start with a man who is bigger

Than John was when John did his baptism thing?

- This Jesus must die, Song of the Priests, JCSS

I dreamed I met a Galilean;

A most amazing man.

He had that look you very rarely find:

The haunting, hunted kind.

I asked him to say what had happened,

How it all began.

I asked again, he never said a word.

As if he hadn't heard.

                        - Pilate’s Dream, JCSS