Structure and Interpretation of Computer Programmers

I make it easier and faster for you to write high-quality software.

Monday, June 23, 2014

Planet of the Apps

Scene: in front of a green screen somewhere in the present day. Our protagonist, freshly burned out from a session of writing dynamically-typed web backend code in vim, looks up from the monitor. In the distance, some way along the beach, they see an odd shape poking out of the sand. Their curiosity piqued, they trudge out under the burning sun toward the edifice.

Running a risk of collapsing through dehydration, finally they are close enough to the object to be able to see through the heat haze that it is the top of a large statue that’s largely covered by centuries of detritus. The only discernible features are a hand holding aloft a chorded keyer, and the stern-browed head of Douglas Englebart.

Oh my God, I’m back. I’m home. All the time it was…we finally really did it. YOU MANIACS! OH DAMN YOU! GOD DAMN YOU ALL TO HELL!

posted by Graham at 04:37  

Saturday, June 21, 2014

Things I believe

The task of producing software is one of choosing and creating constraints, rules and abstractions inside a system which provides very few a priori. Typically we select a large collection of pre-existing constraints, rules and abstractions upon which to base our own: models of computation, programming and deployment environments, everything from the size of the register file to the way in which text is represented on the display is theoretically up for grabs, but we impose limitations in their freedom upon ourselves when we create a new product.

None of these limitations is essential. Many are conventional, and have become so embedded in the cultural practice of making software that it would be expensive or impractical to choose alternative options. Still others have so much rhetoric surrounding them that the emotional cost of change is too great to bear.

So what are these restrictions? Here’s a list of mine. I accept that they don’t all apply to you. I accept that many of them have alternatives. Indeed I believe that all of them have alternatives, and that enumerating them is the first thing that lets me treat them as assumptions to be challenged.

  1. Computers use the same memory for programs and data. I know the alternatives exists but wouldn’t know how to start using them.
  2. Memory is a big blob of uniform storage. Like above, except I know this one isn’t true but that I just ignore that detail.
  3. Memory and bus wires can be in one of two states.
  4. There probably is a free-form hierarchical database available.
  5. There is a thing called a stack and a thing called a heap, and the difference between the two is important.
  6. There is no point trying to do a better job at multiprocessing than the operating system.
  7. There is an operating system.
  8. The operating system, file system, indeed any first system on which my thing is a second system; those first systems are basically interchangeable.
  9. I can buy a faster thing (except in mobile, where I can’t).
  10. Whatever processor you gave me behaves correctly.
  11. Whatever compiler you gave me behaves correctly.
  12. Whatever library you gave me probably behaves correctly.
  13. Text is a poor way to represent a computer program but is the best we have.
  14. The way to write a computer program is to tell the computer what to do.
  15. The goal of the industry for last few decades has been the DynaBook.
  16. I still do not need a degree in computer science.
  17. I should know what my software does before I give it to the people who need to use it.
  18. The universal runtime environment is the C system.
  19. Processors today are basically like faster versions of the MC68000.
  20. Platform vendors no longer see lock-in as a goal, but do see it as a convenient side-effect.
  21. You will look after drawing pictures, playing videos, and making sounds for me.
  22. Types are optional.
posted by Graham at 06:18  

Monday, June 16, 2014

Wristwatches in the Future

[Int: Moscone West convention center third floor ballroom. A presentation is taking place.]

So that was an update on our existing products, which I’m proud to say have never been stronger. Now I’d like to talk to you about our watch. We think you’re gonna love it.

When thinking about recent attempts to make wristwatches by some of our competitors, you’re probably thinking whatever happened to the retina display?

Eliminate Blake

I’ll tell you what happened: you’re looking at it in the wrong size. The pixel density is fine, but the screen’s smaller than it looks on this projector.

Avon Calling!

No, smaller than that.

Ulysse Nardiaaaaaaaaahn!!!!

Hmm, eye strain doesn’t sound like a future thing does it? Shouldn’t we come up with something a bit more ergonomic?

…actually, no, it’s a reasonable compromise. Centuries of user experience research have shown that future people find it most natural to talk into their scaphoid bones. That’s even true when they’re plastic people who don’t actually have scaphoid bones!

Stand by for wrist action!

[Sidenote: No, I will not be apologising for the alt text on that image.]

The technology was originally introduced as part of the struggle to end the Cold War, when one key application was in the unification of Germany.

Rembrandt's Knight Watch.

After seeing how people tried to use these devices, we came up with the breakthrough form factor: five pounds of computer-machined aluminum and an incomprehensible user interface.

This watch is Bullock's.

So that’s the watch. We can’t wait to see what you do with it!

posted by Graham at 01:06  

Sunday, June 15, 2014

Reflections on “Is TDD Dead”

The first thing I noticed that I needed to change as a result of watching the Is TDD Dead? series is that I started out with a defensive mindset. If I believe in the dogma of a rule, then presumably I’m still a beginner who hasn’t yet learned that there are other rules, each of which has limited applicability. So lesson one is to practise more, to find the limitations of the techniques I use, and to understand what to do when those limits are met.

An unsurprising aspect of the discussion was that the thing I call TDD is not the thing that others call TDD. At some point recently I got converted to the Mockist school. Part of me (the part that doesn’t value my social life) is inclined to write a second edition of test-driven iOS development but then keep both editions available, because the style will have changed so much between the two.

Anyway it is more germane to note that none of the three speakers has a lot of time for mocks. I need to understand this, the experiences they have had that I have not, and the things that I do not know about mocks. Perhaps they view the sorts of tests that I build as the structural tests that they would delete once the system is working.

posted by Graham at 05:07  

Tuesday, June 3, 2014

On a re-read you realise this isn’t really about Swift

It’s a bit early to have formed an opinion on a recently-announced programming language, but as the requisite number of people have asked what mine is (i.e. at least zero) I thought I’d type and see what happens.

Rules in programming tend to be bullshit. This is about one-third of a talk I’m giving later in the year, so I’ll leave that train of thought alone in case anyone’s going to be in the audience.

Anyway, knowing this, we can observe the exceptions to any rule people tend to throw at us about programming languages. For example: “Static types for good engineering, dynamic types for exploration“. Make sure your useing you’re type’s good, and notice how many engineering practices come from programmers who know dynamic languages.

We could add “you can’t do good tooling on dynamic languages”. O RLY.

Having thus realised that the rules are nonsense, and that some expert actually sat down and thought about what they wanted to get out of a language in the contexts in which they thought they’d use it. When I did that, I decided on something that goes in entirely the opposite direction to Swift. Starting with ObjC, I’m more likely to end up with Self than with Swift (but then I’ve already told you that I think Sun Microsystems did awesome shit, so that may be no surprise). It probably just means that I’m not an expert, though.

If you’re going to use types, may as well go all-in on using tuples. You’ll probably see plenty of definitions of a tuple, so let me confuse things by adding another:

A tuple is an element drawn from the cartesian product of its member types.

What this means is that unlike boring old-fashioned ordered collections, there’s a known number of things in a tuple and each is of a known type. This is useful for the vexing question of signalling errors, as you can just return something like a (Result?, Error?) like an industrialised society ought to be doing. It also means that almost every situation in which a method’s interface accepts or returns a collection can be replaced with a situation in which it accepts a known number of things of known type.

But anyway, for the most part our programming languages allow us to accidentally introduce problems that we shouldn’t need to solve, but the biggest problems we actually have to solve lie elsewhere.

posted by Graham at 20:39  

Sunday, June 1, 2014

It doesn’t take an Oracle to see that coming

Today has largely been brought to you by nostalgia brought about by this article, reporting on a get-together of former Sun Microsystems employees.

I have never been a former Sun Microsystems employee, and of course now I never will be one. Of all the tech companies I’ve interacted with, Sun is the one I most regret not getting to work with. By the time I dealt with them, they had already put the “crash” in “dot-com crash” but there was still a feeling that they made great things. And besides, they showed that even a pony-tailed Objective-C programmer can be a tech CEO.

I recently talked about the importance of GNU projects, but plenty of other software projects were also important, and Sun had a hand in quite a few of them:

  • Bill Joy worked for them, and most of their early workstation operating systems were based on BSD Unix.
  • In fact while Apollo may have invented the idea that a single person might use a Unix computer, Sun popularised it.
  • I learned how to boot Macs by learning how to program Forth and boot Suns.
  • NFS was the beginning of the separation between your device and your documents.
  • NIS was a bit of an important step on the way to logging in anywhere (its level of baroqueness compared to OAuth has never been accurately gauged).
  • In fact, they pretty much invented cloud computing.
  • Java was quite a big thing for a while.
  • Dtrace is pretty amazing.
  • They even got into standard Unix workstation vendor capitalisation for a while.

It’s likely that much of the interesting stuff at Sun was already over by the time I could’ve worked there, and I certainly experienced a very last-minute replay of some of their history. When I was a student I ‘borrowed’ an Ultra 5 (one of their least good workstations, pretty much a PC with a sun4u SPARC innards) and a SparcStation 5 (one of their most good) to learn about Solaris, SunOS and NeXTSTEP. But it certainly feels like a lot of the future was invented there, even if they were largely following Xerox’s playbook like the rest of the industry.

So tonight, I’ll remember that my control key is in the correct place:

Sun type 5 keyboard

I’ll press L1 and A, then raise a glass to Sun and the job I never had.

posted by Graham at 22:34  

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