Question

I have to code in APL. Since the code is going to be maintained for a long time, I am wondering if there are some papers/books which contain heuristics/tips/samples to help in designing clean and readable APL programs.

It is a different experience than coding in other programming language. Making a function, for example. Small will not help: such a function can contain one line of code, which is completely incomprehensible.

Answer 1

First, welcome to the wonderful world of APL.

Writing readable and maintainable APL code is not much different than writing readable and maintainable code in any language. Any good book on writing clean code is as applicable to APL as any other language, perhaps even more so. I recommend Clean Code by Robert C. Martin.

Consider the guideline in this book that all code in a function should be at the same level of abstraction. This applies to APL 100 times over. For example, if you have a function named DoThisBigTask it should have very few APL primitive symbols in it, and certainly no long complex one-liners. It should just be series of calls to other, lower level functions. If these higher-level functions are all well-named and well-defined, the general drift should be easily determined by someone who does not even know APL. The lowest level functions will be nothing but primitives and will be inscrutable to the non-APLer. Depending on how they are written they may even initially appear inscrutable to a seasoned APLer. However, these low level functions should be short, have no side effects, and can easily be re-written rather than modified if the maintaining programmer is unable to understand the original coding technique.

In general, keep your functions short, well-named, well-defined, and to the point. And keep the lines of code even shorter. It is much more important to have well-defined and well-documented functions than it is to have well-written or well document lines of code.