Across and down

All programming languages have rules. These rules define what can be done and what cannot be done in a valid program. Some languages even have rules for certain things that must be done. (COBOL, for example, requires the four 'DIVISION' sections in each program.)

Beyond rules, there are styles. Styles are different from rules. Rules are firm. Styles are soft. Styles are guidelines: good to follow, but break them when necessary.

Different languages have different styles. Some style guidelines are common: Many languages have guidelines for indentation and the naming of classes, functions, and variables. Some style guidelines are unique to languages.

The Python programming language has a style which limits line length. (To 80 characters, if you are interested.)

Ruby has a style for line length, too. (That is, if you use Rubocop with its default configuration.)

They are not the first languages to care about line length. COBOL and FORTRAN limited line length to 72 characters. These were rules, not guidelines. The origin was in punch cards, and the language standards specified the column layout and specifies 72 as a limit. Compilers ignored anything past column 72, and woe to the programmer who let a line exceed that length.

The limit in Python is a guideline. One is free to write Python with lines that exceed 80 characters, and the Python interpreter will run the code. Similarly, Ruby's style checker, Rubocop, can be configured to warn about any line length. Ruby itself will run the long lines of code. But limits on line length make for code that is more readable.

Programs exist in two dimensions. Not just across, but also down. Code consist of lines of text.

While some languages limit the width of the code (the number of columns), no language limits the "height" of the code -- the number of lines in a program, or a module, or a class.

Some implementations of languages impose a limit on the number of lines. Microsoft BASIC, for example, limited line numbers to four digits, and since each line had to have a unique line number, that imposed an upper bound of 10,000 lines. Some compilers can handle as many lines as will fit in memory -- and no more. But these are limits imposed by the implementation. I am free, for example, to create an interpreter for BASIC that can handle more than 10,000 lines. (Or fewer, stopping at 1,000.) The language does not dictate the limit.

I don't want the harshly-enforced and unconfigurable limits of the days of early computing. But I think we could use with some guidelines for code length. Rubocop, to its credit, does warn about functions that exceed a configurable limit. There are tools for other languages that warn about the complexity of functions and classes. The idea of "the code is too long" has been bubbling in the development community for decades.

Perhaps it is time we gave it some serious thought.

One creative idea (I do not remember who posed it) was to use the IDE (or the editor) to limit program size. The idea was this: Don't allow scrolling in the window that holds the code. Instead of scrolling, as a programmer increased the length of a function, the editor reduced the font size. (The idea was to keep the entire function visible.) As the code grows in size, the text shrinks. Eventually, one reaches a point when the code becomes unreadable.

The idea of shrinking code on the screen is amusing, but the idea of limiting code size may have merit. Could we set style limits for the length of functions and classes? (Such limits and warnings already exist in Rubocop, so the answer is clearly 'yes'.)

The better question is: How do limits on code length (number of lines) help stakeholders? How do they help developers, and how do they help users?

The obvious response is that shorter functions (and shorter classes) are easier to read and comprehend, perform fewer tasks, and are easier to verify (and to correct). At least, that is what I want the answer to be -- I don't know that we have hard observations that confirm that point of view. I can say that my experience confirms this opinion; I have worked on several systems, in different languages, splitting large functions and classes into smaller ones, with the result being that the re-designed code is easier to maintain. Smaller functions are easier to read.

I believe that code should consist of small classes and small functions. Guidelines and tools that help us keep functions short and classes small will improve our code. Remember that code exists in two dimensions (across and down) and that it should be moderate in both.