Some (More) Thoughts on Coding Style

[*]Strategic Scala Style: Conciseness & Names. In this article Li Haoyi raises the point: how you name something is based not just on what that thing is, but how you expect it to be used.

Recently I came across an insightful article on coding style[*] and this triggered some good conversations about coding conventions. The ensuing discussions made me appreciate that coding conventions are much more easily understood when viewed as part of the overall coding style.

So, partly as an exercise to ensure that my personal style is reasonably well fleshed out, the following is a description of my own coding style for projects that I lead.

Essential Elements

There are a couple of points of style that are essential; that is, they are both necessary and ubiquitous to all coding.

Code must be written to be readable

[†]Note: 'humans' is plural; the person who reads the code many not recall that much about the person who wrote that code – sometimes even within single-author projects…

Any code that lives to see the end of the day, will probably live far longer than originally imagined. Also any code that lasts longer than a day is quite likely to be read by humans[†] more often than it will be parsed by compilers. Choose the style to match the needs of the more important audience.

Compilers can make sense out of almost anything that is syntactically correct, and more importantly (so long as one adheres to the language definitions) compilers will suffer in silence. Yes, humans can puzzle out the logic in almost anything, but humans are also fickle beasts who will complain when tasks are made more difficult than necessary.

Make the code easy to read, and let the compilers do the work they were created to do. Make the code easy to read, so when, inevitably, you need to come back and fix up an update, it will be a lot easier for you to do the work you need to do.

Understand and follow preexisting style

When in Rome, live as the Romans do. When elsewhere, live as they live elsewhere.

—St. Ambrose

Any time you are working with existing code, be mindful of whatever style exists within that code; you may not like it, you may want to work to improve it, but you need to honor the style that is already there.

No matter how beautiful the poetry, it does no good to throw down a Shakespearean sonnet in the middle of a logic test. Living with and working with whatever is the style of the existing code is a higher priority than personal preference, even higher than the following prescriptions.

Enhanced Elements

The remaining elements of coding style are still important to good code, but rather than being essential to any code, these elements can enhance the quality of the resulting code.

Whitespace is significant

Civilizations spent hundreds of years perfecting the art of written communication in book form and later in journals and newspapers. One of the lessons learned was that the layout greatly affects how the reader absorbs the content. Do not forget this lesson just because the display is made of glass rather than paper.

The reader uses the visual cues of whitespace to pick up patterns in the material. The space between the parts sets up a rhythm that the readers can recognize at a glance, even before they focus to read the content.

Indentation is key

The whitespace at the beginning of the lines of code is just as important as any other whitespace, but there is more to good indentation than just white space.

A good indentation scheme reveals the intended structure of the code. The coding style should draw attention to that structure. It should be clear from how the indentation is laid out what is the intended structure of the function. Note: of course (other than Python and FORTRAN) the specific details of indentation is not binding on the compilers so it is possible that the source layout does not actually match the actual structure within the resulting executable, but a clear layout should make it easier to recognize when the executable does not behave as the source expects.

Use parentheses with purpose

It is possible to just rely on the existing rules of associativity. However, this would be an example of writing for the compiler as opposed to writing for the reader.

Use parenthesis to establish the order of operations you designed – unless you really do intend to be careless about your calculations… Remember, language standards may evolve over time including order of operations whose ambiguities may be addressed, and it is rare that the application code is truly agnostic. Make your intentions clear in the original source, or risk a tricky troubleshooting session later when subtle shifts in definition lead to differing results.

Where possible, use the indentation of parentheses to make the underlying structure clear. If it is not easy to fit everything on one line, intent the closing parentheses just as you would intent closing braces of code blocks.


Pay attention to layout

Pay attention to the tools the readers will use to view the code. Strive to make the key elements for whatever the readers focus on are readily found on the same "page" as the code. In other words, where possible try to keep the reader from having to scroll.

Refactoring code can be a most effective tool for maintaining useful degrees of modularization – whenever the code stretches over several pages to read then it is worth considering how to refactor.

The same thing is also as true horizontally as it is vertically – long lines become especially difficult to read.

Write succintly

The programmer is not writing a novel. A readable program is not so much even a novella with character development and plot twists, but rather more like a set of terse poems relying heavily on the readers' recognition of idioms and patterns.

The reader will use the code only to understand the program. This source code is not the place the reader is looking for an indepth critique of algorithms. Keep the source files focused on making the current implementation clear and easy to understand. If there is a need for a deep dive into some topic of related interest, that can live in its own, separate, piece of documentation.

End Thought

Compilers may be arcane and picky, but they are patient.

Programmers' patience is a very rare commodity. Be mindful to make good use of this essential resource.