A few days before leaving work for a week and a half of flying and cruising to escape frigid Pennsylvania, I came across a Joe Armstrong quote during my regularly scheduled slacking off on twitter and Hacker News. I’d come across a couple times before, only this time I noticed it had a source link. This led me to discovering (and shortly thereafter, buying) Peter Seibel’s “Coders at Work – Reflections on the Craft of Programming”. I loaded it onto my nook, and off I went.

The book is essentially a collection of interviews with a series of highly accomplished software developers. Each of them has their own fascinating insights into the craft and its rich history.

While making my way through the book, I highlighted some excerpts that, for one reason or another, resonated with me. I’ve organized and elaborated on them below.

Incremental Changes

I’ve seen young programmers say, “Oh, shit, it doesn’t work,” and then rewrite it all. Stop. Try to figure out what’s going on. Learn how to write things incrementally so that at each stage you could verify it.
– Brad Fitzpatrick

I can remember doing this to myself when I was still relatively new to coding (and even worse, before I discovered source control!). Some subroutine or other would be misbehaving, and rather than picking it apart and figuring out what it was I’d done wrong, I’d just blow it away and attempt to write it fresh. While I might be successful, that likely depended on the issue being some sort of typo or missed logic; if it was broken because I misunderstood something or had a bad plan to begin with, rewriting it would only result in more broken code, sometimes in more or different ways than before. I don’t think I’ve ever rewritten someone else’s code without first at least getting a firm understanding of it and what it was trying to accomplish, but even then, breaking down changes piece by piece makes it all the easier to maintain sanity.

I do still sometimes catch myself doing too much at once when building a new feature or fixing a bug. I may have to fix a separate bug that’s in my way, or I may have to make several different changes in various parts of the code. If I’m not careful, things can get out of hand pretty quickly, and before I know it I have a blob of changes strewn across the codebase in my working directory without a clear picture of what’s what. If something goes wrong, it can be pretty tough to sort out which change broke things (or fixed them). Committing changes often helps tremendously to avoid this sort of situation, and when I catch myself going off the rails I try to find a stopping point and split changes up into commits as soon as possible to regain control. Related changes and fixes can always be squashed together afterwards to keep things tidy.

Specifications & Documentation

Many customers won’t tell you a problem; they’ll tell you a solution. A customer might say, for instance, “I need you to add support for the following 17 attributes to this system. Then you have to ask, ‘Why? What are you going to do with the system? How do you expect it to evolve?’” And so on. You go back and forth until you figure out what all the customer really needs the software to do. These are the use cases.
– Joshua Bloch

Whether your customer is your customer, or your CEO, the point stands: customers are really bad at expressing what they want. It’s hard to blame them, though; analyzing what you really want and distilling it into a clear specification is tough work. If your customer is your boss, it can be intimidating to push back with questions like “Why?”, but if you can get those questions answered you’ll end up with a better product, a better understanding of the product, and a happy customer. The agile process of doing quick iterations to get tangible results in front of them is a great way of getting the feedback and answers you need.

The code shows me what it does. It doesn’t show me what it’s supposed to do. I think the code is the answer to a problem. If you don’t have the spec or you don’t have any documentation, you have to guess what the problem is from the answer. You might guess wrong.
– Joe Armstrong

Once you’ve got the definition of what you’ve got to build and how it’s got to work, it’s extremely important that you get it documented. Too often, I’m faced with code that’s doing something in some way that somebody, either a customer or a developer reading it, takes issue with, and there’s no documentation anywhere on why it’s doing what it’s doing. What happens next is anybody’s guess. Code that’s clear and conveys its intent is a good start towards avoiding this sort of situation. Comments explaining intent help too, though making sure they’re kept up to date with the code can be challenging. At the very least, I try to promote useful commit messages explaining what the purpose of a change is, and reference a ticket in our issue tracker which (hopefully) has a clear accounting of the feature or bugfix that prompted it.

Pair Programming

if you don’t know what you’re doing then I think it can be very helpful with someone who also doesn’t know what they’re doing. If you have one programmer who’s better than the other one, then there’s probably benefit for the weaker programmer or the less-experienced programmer to observe the other one. They’re going to learn something from that. But if the gap’s too great then they won’t learn, they’ll just sit there feeling stupid.
– Joe Armstrong

Pairing isn’t something I do much. At least, it’s pretty rare that I have someone sitting next to me as I code. I do involve peers while I’m figuring out what I want to build as often as I can. The tougher the problem, the more important it is, I think, to get as much feedback and brainstorming in as possible. This way, everybody gets to tackle the problem and learn together, and anyone’s input, however small it might seem, can be the key to the “a-ha” moment to figuring out a solution.

Peer Review

I think an hour of code reading is worth two weeks of QA. It’s just a really effective way of removing errors. If you have someone who is strong reading, then the novices around them are going to learn a lot that they wouldn’t be learning otherwise, and if you have a novice reading, he’s going to get a lot of really good advice.
– Douglas Crockford

Just as important as designing the software as a team, I think, is reviewing it as a team. In doing so, each member of the team has an opportunity to understand how the system has been implemented, and to offer their suggestions and constructive criticisms. This helps the team grow together, and results in a higher quality of code overall. This benefits QA as well as the developers themselves for the next time they find themselves in that particular bit of the system.

Object-Oriented Programming

I think the lack of reusability comes in object-oriented languages, not in functional languages. Because the problem with object-oriented languages is they’ve got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle.
– Joe Armstrong

A lot has been written on why OOP isn’t the great thing it claims to be, or was ever intended to be. Having grappled with it myself for years, attempting to find ways to keep my code clean, concise and extensible, I’ve more or less come to the same conclusion as Armstrong in that coupling data structures with behaviour makes for a terrible mess. Dividing the two led to a sort of moment of clarity; there was no more confusion about what methods belong on what object. There was simply the data, and the methods that act on it. I am still struggling a bit, though, on how to bring this mindset to the PHP I maintain at work. The language seems particularly ill-suited to managing complex data structures (or even simple ones – vectors and hashes are bizarrely intertwined).


You should read [Elements of Style] for two reasons: The first is that a large part of every software engineer’s job is writing prose. If you can’t write precise, coherent, readable specs, nobody is going to be able to use your stuff. So anything that improves your prose style is good. The second reason is that most of the ideas in that book are also applicable to programs.
– Joshua Bloch

My advice to everybody is pretty much the same, to read and write.

Are you a good Java programmer, a good C programmer, or whatever? I don’t care. I just want to know that you know how to put an algorithm together, you understand data structures, and you know how to document it.
– Douglas Crockford

This is what literate programming is so great for –
I can talk to myself. I can read my program a year later and know exactly what I was thinking.
– Donald Knuth

The more I’ve program professionally, the clearer it is that writing (and communication in general) is a very important skill to develop. Whether it be writing documentation, putting together a project plan, or whiteboarding and discussing something, clear and concise communication skills are a must. Clarity in writing translates into clarity in coding as well, in my opinion. Code that is short, to the point, clear in its intention, making good use of structure and wording (in the form of function and variable names) is far easier to read and reason about than code that is disorganized and obtuse.


I tried to make familiarity with Knuth a hiring criteria, and I was disappointed that I couldn’t find enough people that had read him. In my view, anybody who calls himself a professional programmer should have read Knuth’s books or at least should have copies of his books.
– Douglas Crockford

… Knuth is really good at telling a story about code. When you read your way through The Art of Computer Programming and you read your way through an algorithm, he’s explained it to you and showed you some applications and given you some exercises to work, and you feel like you’ve been led on a worthwhile journey.
– Guy Steele

At one point I had [The Art of Computer Programming] as my monitor stand because it was one of the biggest set of books I had, and it was just the right height. That was nice because it was always there, and I guess then I was more prone to use it as a reference because it was right in front of me.
– Peter Norvig

I haven’t read any of Knuth’s books yet, which is something I’ll have to rectify soon. I don’t think I have the mathematical background necessary to get through some of his stuff, but I expect it will be rewarding nonetheless. I’m also intrigued by his concept of literate programming, and I’m curious to learn more about TeX. I imagine I’ll be skimming through TeX: The Program pretty soon now that I’ve finished Coders at Work :)