Keeping things simple

Musings on simplicity in programming.

published 2015-Mar-10

Lately I've been trying to figure out how to write shorter programs. Or, more generally, how to design simple solutions.

I often hear that "less is more", that you should KISS and follow YAGNI, yada yada. A small program is easy to understand and cover with tests. A simple API is pleasant to use. But that's still abstract. What's a practical recipe for keeping things small? We might define two attack vectors:

Scope Reduction

This approach is as simple as it gets. Saying no to a problem spares you from having to implement a solution.

Sometimes you need to draw a line and say that this feature shouldn't be in the library, the user should write a bit of glue code instead. Or that this extra concept is not worth the code savings it produces.

For programs with one well-defined function, this is known as the Unix philosophy and is straightforward to follow. But it's also useful for programs with a potentially unbounded scope, like a data modeling library or a language compiler. A surprising number of ideas turns out to be dead weight after a while.

Curiously, this takes willpower, or restraint, which seems to be an unpopular feature with developers. Adding moving parts is interesting. Being lazy is not enough; you have to apply mental effort to refuse additions and keep things simple.

General Case Solutions

Programs with an unbounded scope accumulate complexity as a result of tackling new problems, usually in response to feedback. Feedback tends to focus on specific use cases. Addressing them individually leads to accumulating special case solutions, even for problems that could be addressed with a general case feature, if this class of problems could be foreseen in advance.

Feature feedback also indicates that the application scope perceived by users outranges its design scope. Including a new feature or addressing a new use case would expand its implementation scope, which should be defined by the design scope, not the other way around. Which means agreeing to expand a program should begin by exploring and expanding its design scope, as if the system was being designed anew.

Therefore the default reaction to a feature request should be figuring out what class of problems it represents, and either refusing it entirely, or addressing the entire class instead.


Every person is different, but for me, both things boil down to restraint. It's tempting to add new moving parts. It's tempting to address a special case instead of figuring out a wider class of problems and a solution that covers them all. You need to stop yourself, take a step back, and remember that taking the time to find the right problem to solve will spare you from throwing solutions away.