Lua: technical note 0

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Technical Note 0

How to write a Lua Technical Note

There are no official guidelines for writing a Lua Technical Note. You may read Author's Guide and On the Elements of a Technote, from the Macintosh Technical Notes, but read these documents just for an idea of what technical notes look like; Lua Technical Notes are much more informal.

Below is a personal (and self-referential!) view of how to write LTNs.

How to write an LTN

by Reuben Thomas

Abstract

An LTN should have the following structure:

Abstract
The problem - Motivation and statement
The solution - Description
Explanation and justification
Weaknesses and suggested improvements
Conclusion

The problem

Lua is a brilliantly economical tool for solving many programming problems. Unfortunately, its economy and flexibility of design can confuse the newcomer: they may find a clumsy solution to their problem, or worse, not see one at all, when there is a simple and elegant solution waiting to be found. Unlike users of most languages, who simply program in them, Lua programmers will often want to embed, interface to, or even change Lua.

Various libraries and tools have grown up to meet many of these needs, such as tolua, CGILua and LuaSocket. However, some needs are more abstract, and cannot easily be met by a tool or library; questions such as: How can I integrate Lua into my C++ program? How can I interface Lua to another language? How can I avoid pausing my game for garbage collection? Questions like these are best tackled by HOWTO-like documents, and this is what the LTN series aims to do. But how should LTNs best be written in order to meet this need?

An LTN should have the following properties:

It should address a real need. As a rule of thumb, if you can be motivated to write an LTN, it's probably addressing a real need, though it's even better if others have asked for solutions to the problem it addresses.
It should be brief. This allows others to read, understand and use the knowledge it contains as quickly as possible; or, on the other hand, to discard it if it's no good to them. As part of this, it should not be necessary to read the whole LTN to know if it's what you need.
It should be authoritative. An inaccurate or badly thought out LTN may well be worse than nothing. Again, if you feel like writing an LTN, you'll probably know what you're talking about. The Lua designers act as editors for the series, which also helps.

The solution

There are two parts to the solution: form and content. The content is up to the author; the suggested form for an LTN is as follows:

Abstract: Summarise the LTN.
The problem: Motivate the problem: why is it important. End with a clear statement. This will help both you and the reader to focus. By the end of this section the reader should know if the LTN is useful for them.
The solution: Describe the solution, without elaborating on the whys and wherefores more than necessary. By the end of this section, a reader who's in a hurry should be able to implement the solution.
Explanation: Explain and justify why you designed your solution the way you did. This will hopefully convince the skeptical and reassure the cautious that your solution is good and you know what you're doing. Peripheral matters and non-critical subtleties can be explored here (but keep it relevant!).
Weaknesses: Discuss weaknesses of your solution, say why they're not critical to its success, and suggest future improvements. This is where you'll really convince the skeptic you know your stuff.
Conclusion: Summarise, and give a wider perspective on the problem and solution.

Explanation

This structure follows standard practice for good technical writing. The simple five-part structure encourages brevity, fits most conceivable LTNs, is simple for the author and reader to follow, and allows most readers to get everything they need from the LTN by starting at the top and reading until they've had enough.

Weaknesses

One size never fits all. The proposed structure will be too detailed for some, not enough for others, and simply irrelevant to others. I have said nothing about how actually to write (see "The Elements of Style" by Strunk and White for clear, brief guidance on this). Nonetheless, if most authors follow this structure, they will hopefully find LTNs easier to write, and readers will certainly find them easier to read because, if nothing else, of their common structure.

Conclusion

Lua's brilliance lies largely in providing generally applicable mechanisms rather than solutions to specific problems. Nevertheless, many problems crop up frequently in the use of Lua. Some of the more concrete ones are addressed by the variety of libraries and tools available; LTNs attempt to address some of the more abstract kind. This LTN proposes a structure for LTNs to make them more likely to be useful.

Finally, Lua programmers and LTN authors alike should always bear in mind the first rule of Lua: "Do it in Lua". Lua almost always provides you with the tools you need to solve your problem; it's just a case of seeing how to use them. You should rarely have to use Lua API seriously, and even more rarely have to change Lua itself. In terms of the three cardinal virtues, Lua ranks laziness above impatience, and impatience above hubris. But of course, hubris is just what it takes to write an LTN!