Monthly Archives: March 2015

An interview with Kevlin Henney

I recently got the opportunity to do an e-mail interview with Kevlin Henney. He is a well-known author, engaging presenter, and a consultant on software development. He was the editor for the book 97 Things Every Programmer Should Know, and has given keynote addresses not just at ACCU but at other conferences as well.

How did you get in to computer programming? Was it a sudden interest? Or was it a slow process?

I was aware that computers could be programmed, and the idea sounded interesting, but it wasn’t until I was able to actually lay hands on a computer that I think it occurred to me that this was a thing that I could do myself.

What was the first program you ever wrote? And in what language was it written in? Also is it possible to provide a code sample of that language?

I can’t remember exactly, but I suspect it probably just printed “Hello” once. I strongly suspect that my second program printed “Hello” endlessly — or at least until you hit Ctrl-C. It was written in BASIC, and I strongly suspect that it was on a UK-101, a kit-based 6502 computer.

These days I am more likely to disavow any knowledge of BASIC than I am to provide code samples in it — but I think you can probably guess what those examples I just mentioned would look like!

What would you say is the best piece of software you’ve ever written? The one you’re most proud of?

Difficult to say. Possibly the proof-of-concept C++ unit-testing framework I came up with a couple of years ago, that I dubbed LHR. I don’t know if it’s necessarily the best, but it incorporated some novel ideas I’m proud of.

What would you say is the best piece of advice you’ve ever been given as a programmer?

To understand that software development concerns the management of complexity.

If you were to go back in time and meet yourself when you were starting out as a programmer, what would you tell yourself?

As a professional programmer? Don’t worry, it’s not all crap. As a schoolboy? Yes, it really can be as much fun as you think it is.

Do you currently have a mentor? And if so, what would you say is the best piece of advice you’ve been given by them?

I don’t currently have anyone I would consider a mentor, but there are a number of people I make a point of shutting up and listening to when they have something to say.

You are well known for giving excellent talks on various topics to do with Software Engineering, I recall the one you did at ACCU Conference last year. How did that come about? And how scary was it to leave the security of a regular 9 to 5 job and go solo?

I worked as a principal technologist at QA, a training and consultancy company, for a few years. Training was part of my job role and that gets you comfortable with presenting and thinking on your feet. Conference presentations are a little different as the objective of a talk and the environment of a conference are not the same as a course or a workshop, but there’s enough overlap that practice at one supports practice in the other.

As a principal technologist at QA I enjoyed a great deal of autonomy and so the transition to working for myself was not as jarring as it might first appear. Meeting people at conferences also opened more opportunities than I had perhaps realised were available when I was associated with a larger company.

I’m not sure I could have gone straight from working for someone to being independent. Actually, that’s not quite true: I went from being an employee to being a contractor many years ago, but I didn’t find that fulfilling.

And following on from that, what advice would you give to someone who’s looking to go it alone?

Make sure you know what your motivation is for going it alone, that your expectations are realistic and that you have some work lined up!

I’m guessing you work from home, if so, how do you keep the balance between work time and family time?

A question I’ve wrestled with for years and still not one I’m sure I have a good answer to! I am, however, far better at turning off than I used to be, recognising that work time is an interruption from family time and not the other way around. As I travel a lot the work–family distinction is often reinforced by whether I’m at home or away, so I try to get more work-related things done when I’m away because it doesn’t distract from family. I notice that when I’m working and at home the context switch can be harder because the context is effectively the same.

How do you keep your skills up to date? Do you get a chance to do some personal development at work?

I attend conferences, I talk to people I meet (and people I don’t meet) and I read. I probably get a lot more breadth than depth, but I temper that by focusing on things that interest me — so I’ll freely admit to being more driven by interest than necessity.

I’ve seen that you contribute to the Boost libraries as well. How did you get involved in that? And what advice would you give to a prospective developer looking to get involved in such a project? Or any open source project for that matter.

My involvement came about primarily because of my involvement in the C++ standards committee and writing articles about C++. That said, although I have a continued interest in Boost, I am no longer an active contributor, having long ago passed maintenance of my contributions to others.

As for advice on doing it: if you think you want to get involved, then you should. It’s worth spending your time familiarising yourself with the ins and outs and mores of your project of interest, asking questions, getting a feel for what you can best contribute and how. If you’re a developer, don’t assume it’s going to be coding where you stand to learn or contribute the most — maybe it’s code, maybe it’s tests, maybe it’s documentation, maybe it’s something else.

What would you describe as the biggest “ah ha” moment or surprise you’ve come across when you’re chasing down a bug?

That good practice I ignored? I shouldn’t have ignored it. I don’t know if that’s the biggest surprise — in fact, it’s the exact opposite — but it’s the biggest lesson. There’s nothing quite like the dawning, creeping realisation that the bug was easily avoidable.

Do you have any regrets as a programmer? For example wishing you’d followed a certain technology more closely or something like that?

Listing regrets or indulging in regret is not something I really do, which I would say is no bad thing — and not something I regret.

Where do you think the next big shift in programming is going to come in?

Realising that there are few big shifts in programming that change the fact that, ultimately, it’s people who define software. We have met the enemy and he is us.

Are you working on anything exciting at the moment? A new book? Or a new piece of software?

There’s a couple of code ideas I’m kicking around that I think are quite neat, but perhaps more for my own interest, and a couple of book projects that have my eye.

Finally, what advice would you offer to kids or adults that are looking to start a career as a programmer?

Look at what’s happening now, but also look at what’s gone before. If you can figure out they’re related, you’re doing better than most.

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Why version control is a life saver…

It was late, and I’d done a long day up to that point. And I was mucking about with some inconsequential code. In fact, I was trying to delete the directory, as I’d finished what I was doing with it.

So I executed that fateful command: rm –rf parserdemo/ *

Now I’m sure almost all my regular readers will know straight away where I went wrong. I didn’t immediately. I was tired, and aching to get home, but after two minutes I thought, “that directory wasn’t that big!!” so I control-c’d it and did an ls.

It wasn’t a pretty sight. Almost every project I’d worked on had gone from my dev directory. Even more worrying was the work I was working on that morning had gone. Now I usually commit my code at the end of the day, (when I remember) so I cd’d in to the the project’s directory, looked ok, maybe I cancelled it in time, but no! I did a git status and got a nasty error message.

Fortunately for me, I actually committed the work earlier that day as I’d finished the ticket I was working on. So fortunately I could blat the directory, re-clone the project and check out against the appropriate branch and sure enough there was the code I’d lovingly written that morning.

The moral of this lesson?

Well first of all, be VERY CAREFUL using rm –rf, because it will just chomp through anything and everything if you’re not careful.

Secondly, if you don’t use version control, then do so.  It’s there for a VERY GOOD REASON.  And these days you can have your code hosted for free on github or bitbucket or any number of free source code repository sites.

Thirdly, commit your changes often. Because you never know when you need to roll back to something you did by mistake. With git this is very easy, I don’t have experience of other version control systems. I do recall using one tool that you had to check out individual files, then check them back in again against a central repository, you didn’t have the code on your hard disk the way you do with git. But I digress.

The fact of the matter is, I was tired and a wee bit irritable by that point of the day, and I hadn’t realised what I’d done until I looked at the command more carefully. But it’s the kind of mistake you’ll only make once.  Hopefully…