Code Reading: The Open Source Perspective
A few books are tackling this subject, including Coder to Developer and Programming Language Pragmatics. These books don't teach you much about a particular language in the way that an introductory text would. Instead, you grow as a skilled developer by studying them and learning from them. That's one of the key things that people are talking about lately, that to be a strong developer requires more than a working knowledge of a language. It requires a familiarity with the strengths, weaknesses, and core features of a language and the base libraries to be efficient.
Code Reading: The Open Source Perspective is one of these books in this small but growing library. In it, Diomidis Spinellis takes you through a large body of code and focuses on several languages, techniques, and facets of development that differentiate strong developers from weak ones. What I like about this book is how much it covers, how practical the information is, and how much Spinellis teaches you. You wont learn a language, which is the complaint of some people who read this book, but if you know one or two you'll be a better programmer.
Perhaps one of the most telling things about the book is that it draws heavily from NetBSD source code, and features over 600 examples to make the point. Examples are often annotated using NetBSD as a reference. This makes sense, because NetBSD is a large project that's relatively stable and mature. Everything from how to define a C structure consistently and sanely to UML diagrams and build systems are covered, making this truly a developer's book. However, even Windows and Mac OS X developers will benefit, despite the BSD focus.
Chapter 1 introduces some of the basic tenets of the book, namely that code is literature and should be read as such. All too often people only read code when they have a specific problem to solve or want to get an example of an API. Instead, if you read code frequently you'll always be learning things and improving your skills. Also, Spinellis discusses the lifecycle of code (including its genesis, maintenance, and reuse), which simply must be taken into account if code is to be good. Poorly skilled developers forget these things and just slap it together, never thinking ahead.
In Chapter 2, a number of concepts basic to any programming language are covered, including the basic flow-control units common to many languages. The book focuses on C, with additional coverage given using C++, Java, and a few other things thrown in for good measure. As such, these chapters -- in fact the whole book -- focuses on concepts common to these languages but absent in some other languages, like Scheme or LISP. One neat section is called "refactoring in the small." It illustrates the real value of the book nicely, in showing you various ways to organize your code and your thoughts for various effects. Oftentimes a book will only teach you one way (which doesn't always suit your needs), and Spinellis' examples do a nice job of escaping that trap, not just here but throughout the book.
Chapter 3, "Advanced C Data Types," focuses on some language-specific matters. These are pointers, structures, unions and dynamic memory allocation, things that most people who code in C may use but only some truly understand well. Again, a somewhat basic chapter, but useful nonetheless. Make sure you read it; chances are you'll learn a thing or two.
In Chapter 4, some basic data structures (vectors, matrices, stacks, queues, maps and hash tables, sets, lists, trees and graphs) are covered. This is an important chapter since it helps you see these structure in real-world use and also helps you understand when to chose one structure over another. While Knuth, CLRS, or other algorithms and data structures texts cover these, they often do so in isolation and at a theoretical level. While their coverage is short, it's to the point and usable by anyone with a modest understanding of C.
Chapter 5, "Advanced Control Flow," the last chapter that deals with actual programming information, is another useful one. Again, short but to the point, this chapter covers things like recursion, exceptions, parallelism, and signals, all topics that have warranted their own books (or major sections in other books) but which are covered in a single chapter here. Still, seeing them side-by-side and in the context of each other and in real-world use provides some justification for the compact presentation.
The remaining chapters of the book go well beyond a normal programming book and focus on projects. These chapters complement the first bunch nicely by focusing on the organization of your code and projects. Chapter 6 deals specifically with many of the commonly identified (but rarely taught) things like design techniques, project organization, build processes, revision control, and testing. A number of things that aren't covered include defining and managing requirements for a release and their specifications, basics on how to use autoconf and automake, and instead rips through a whole slew of topics quite quickly.
Chapter 7 is sure to be controversial for some people: it covers "Coding Standards and Conventions." Some people seem to be big fans of the "if it feels good, do it" style of programming, and instead of writing sane, usable code, what they produce is buggy and messy. This chapter teaches you tried and tested methods of naming files, indentation (and how to do so consistently using your editor to help), formatting, naming conventions (for variables, functions, and classes), as well as standards and processes. The style and standards are (as you would expect) based on NetBSD, which differ slightly from GNU and Linux standards, as well as commonly found Windows practices. However, I think you'll agree that the style is readable with minimal effort, and that goal, coupled to consistency, is paramount in any standard.
Chapter 8 introduces you to documentation, including the use of man pages, Doxygen, revision histories, and the like. Also included are hints at using diagrams for added value. One thing I don't like about this chapter is the opening quote, which sets a bad precedent. It blithely suggests that bad documentation is better than none, which is highly questionable. Misleading docs can be worse than no docs at all, since someone without docs will have to dig through the code in front of them to understand it. Someone with bad docs will rely on the docs and wonder what's broken when things go awry.
Chapter 9 focuses on code architecture, such as class hierarchies, module organization, and even core features like frameworks to chose. This chapter covers a lot of material, and is, despite its size, simply too terse on many of these subjects. It serves as a decent introduction, but doesn't go very far in some places, considering the importance of the material. However, like much of the book, it's a good introduction to the topics at hand.
Chapter 10 also features a lot of good things to know. Granted, you could pick them all up with a lot of hard work and scouring for information, but it's easier to have them presented to you in a cohesive format. The chapter discusses code reading tools, things that you use to help you dig around a large body of code. One you get over a few source files, even if you have well-organized code and interfaces, many changes can require that you inspect the data path. You can do this manually, or you can be assisted with tools. Tools like regular expressions, grep, your editor -- Spinellis shows you how to make use of all of them when you write code. A lot of tools I've never used (but have heard about) are featured, and their use is demonstrated, but of course many tools are simply ignored, focusing on popular ones that will work for most people.
Finally, all of the above is brought together in Chapter 11, "A Complete Example." A small tour of a large, complex piece of code is taken (34,000 lines of Java) as the author makes changes. It's unfortunately in Java, when so much of the book focused on C (why couldn't they have been consistent examples?), but it works. The example itself could have covered a few more things, such as a proper JUnit example, but overall I'm pleased with it.
Overall, Code Reading: The Open Source Perspective is ambitious and worthwhile, both as a complement to a bookshelf of study that includes The Practice of Programming and Design Patterns, and to someone who is growing tired of books on learning a language. At times it feels like the author promised more than he wound up delivering, but it serves as an introduction to a large number of topics. You wont learn a language, and you wont be able to get as much out of the book if you don't engage it with practice, but it's a useful book to get started on the road from being someone who knows a language or two to someone who is a developer, ready to contribute to a team and work on large projects. Never underestimate the skills required to be a good developer, because they go well beyond knowing how to use a language.
You can purchase Code Reading: The Open Source Perspective from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
When I see that develop in someone, then I know they are going to the next level. When I don't see it after time, I know they will never evolve.
You can tell a great deal about the maturity of a programmer by the quantity, and quality, of comments.
Unfortunately, some experienced programmers write like ee cummings, and others like avant-guard poets.
Have you read my blog lately?
You can usually tell someone who's been writing a lot of code by how they write code.
/.
I looked at the slashcode once and I'm fairly sure Taco worked on debugging serial port line noise before starting
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
The amount of comments in code is interesting. It kind of starts at an extreme, then moves slowly to the middle, happy land.
If you started programming, you either chose to comment a lot, or not at all. "A lot", because you were never sure what your code was doing, and always needed the reference. Or "not at all", because you could make sense of the code very well.
Then you start your first big project. For the big commenter, he realizes after getting quite a bit of work done that a lot of time was "wasted" on comments. ("// This line increments the 'i' variable by 1".) Further, these comments seem way too obvious. For the non commenter, they get lost easily and wish they commented more.
So it goes in the opposite direction from when it started. The big commenter comments way less, and the non commenter comments way more.
Then it repeats. Eventually the programmer gets the happy medium of the right amount of comments.
This has been my experience, in my own code, and checking other people's code. Thoughts?
Personally I hate wasting time writing a function to do something only to find out 10 days later... the language already comes with a library that does the exact same thing. Experience do count there.
I disagree when writing Java and C#. These languages are inherintley readable if you write clean, understandable code with good variable names. Comments should be used whey you implement something that you can't understand by reading the code. Its quickker for me to read clean code, and comments often get in the way and get outdated and hurt more than they help. Maintainance is the Iceburg.
Most critical is managing complexity. Large, complex functions are bad - they have more bugs, they are harder to maintain, harder to bug fix (a change has more likelyhood of breaking something else). If a function has grown beyond a hundred lines of (real) code, it is almost certainly too large. If it has more than 4 levels of nesting, it is too large.
Comments also matter. It's easy to code a couple of thousand lines of fresh code over a weekend if you get in the groove. It is almost impossible to unpick it one year later if you didn't comment it as you go.
Variable and function names should be expressive. No single letter variable names! No obscure combinations of letters like words with no vowels (fnct could be function or function control, or even Function Numerical Constant Type). And personally I find that reverse Hungarian notation can be more trouble than it's worth. puiAnnoying!
Build in automatic checks on everything. If a pointer to a function should never be null, check it and stop if it is. If a variable should only have values 1 -> maxIterations, then check it. If you (or anyone else) ever breaks that assumption, the code will flag it for you.
Beyond that, nothing beats good design, especially designs where extending the original work is easy. So many designs end up as tangle knots of conflicts because they ended up trying to solve problems that the original code base never envisaged.
Cheers,
Toby Haynes
Anything I post is strictly my own thoughts and doesn't necessarily have anything to do with the opinions of IBM.
From someone who's had a hand in dealing with function pointers named StupidSuckingGlobalCallbackFunction, trust me, the subject of this post is very, very, very wrong.
I pity the foo that isn't metasyntactic
- Project was originally a quick hack. It lives well past its prime, gets modded extensively to handle changes going on in the real world (new devices, competition, etc.). Abstractions are added where necessary. Some hacky ugliness lives at fringes, but after umpteen releases and way too much backwards compatibility customers are still buying it.
- Project was a grandiose dream by an analyst. Before any functionality exists, everything is abstracted to the max. 10-inch thick binders full of API's are published before the product actually does anything. The abstractions usually turn out to be wrong, and after many years (and little functionality) either the abstractions get twisted around at great expense to reach functionality, or the project dies in heaving paroxysms.
. Reading the experienced coder's comments is always good. They know the history and want to pass on the lessons learned to whoever will look.If the expression itself requires a comment, then it is not being expressed clearly enough. It should be rewritten.
If the expression is clear, but does not make sense in the context, appears suboptimal, or otherwise thwarts the reader's expectations, THEN I'll comment.
Real world project comments...
I would say the concept of getting paid for programming.
"We can't solve problems by using the same kind of thinking we used when we created them." -- Albert Einstein
The author is probably referring to the way Scheme and LISP are "missing" static type checking, in much the same way I am "missing" a hole in the side of my head.
The claim that something is missing would be more compelling if they weren't "missing" it on purpose, and the trend wasn't swinging in the dynamically-typed (or, as I think of it, "value typed" as opposed to "variable typed"; whatever you do it's wrong to call it "weakly typed") language's favor anyhow.
(Variable-based-typing's only hope is that the type-inferencing languages penetrate into the mainstream before the recoginition that variable-based-typing isn't free does, that being the fundamental misconception keeping it afloat. (Once you ack. the obvious point that it is not free, and is in fact quite expensive, both in actual effort and in massively underestimated opportunity costs, you are suddenly able to consider it in terms of costs and benefits, and the cost/benefit analysis generally does not work out in its favor when done dispassionately, though there are exceptions.))
All I gotta say is that if you use {
this {
style {
of indention
}
}
}
You are a newbie.
No way! I have been coding for 30 years...
It makes more sense to code
if (test) {
statement1
} else {
statement2
}
because the eye can immediately see from the 'if' and 'else' statements alone that a block of conditional code follows. Having the braces on the same line also marks out the lines as special: flow control code. I find that
if (test)
{
statement1
}
else
{
statement2
}
simply adds pointless extra lines to code, with no gain in readability.
But many "newbies" such as Kernighan, Ritchie, and Torvalds all highly recommend the One True Brace (OTB) style. It's the one used in the K&R's C book, among other things. In other words, some of the people MOST exerienced with C use this style.
There are serious advantages to the OTB style. In particular, it eliminates useless white space so that you can actually see more vertical text simultaneously -- even with big screens that's helpful.
If you want to use a different style, go ahead! If you're the lead, I'll gladly use your style. But in programs I lead, I'll continue to use OTB and expect others to follow suit. Oh, and I've been using C since 1985, so !newbie.
- David A. Wheeler (see my Secure Programming HOWTO)
Linus Torvalds (Linux kernel)
W. Richard Stevens (Advanced Programming in the UNIX Environment and UNIX Network Programming)
Brian W. Kernighan (C Programming Language co-author)
Dennis Ritchie (C Programming Language co-author)
Gamma, Helm, Johnson, and Vlissides (Design Patterns)
Hmmm. You are a newbie. Kernighan and Ritchie wrote the book on C, literally, and the ISO C standard still uses their style. The opening brace is only by itself when starting a function body. In all other cases, it shares the line.
From Structure and Interpretation of Computer Programs by Abelson and Sussman:
"Programs should be written for people to read, and only incidentally for machines to execute."
Both consistency and good comments are good traits. I find understandable function and variable names are essential as well.
I believe that language familiarity has little to nothing to do with being a good programmer. A more familiar programmer can program faster but programming principles remain the same across all languages.
Smaller, simpler code is inherently less likely to contain bugs, runs faster, and is easier to troubleshoot.
If programmer A develops 1000 lines of code per day and programmer B develops 10 lines of code per day and both programs do the same thing I will pick programmer B every time (normal lines of code, not contest entries with runon lines and things)
Coding Blog
To think of code as literature is actually a non-obvious and striking idea.
The essence of literature is communication. I've been writing C and C++ for years, constantly fine-tuning and refining code and documentation, line by line, paragraph by paragraph. And how apropos to realize that the point is to express the thought so clearly and concisely that any reader (including yourself three weeks from now) will grasp it as close to immediately as possible.
That means you have to think clearly in order to code clearly. This matters more than almost anything else.
Too much documentation is just as bad as too little, since it obscures the intent of the code. How much is just enough? It takes years of thoughtful practice to know that.
Everyone is posting their favorite rules about coding standards. Most young programmers apply standards as rigid as they are incomplete. I have only two rules:
1) Call everything by its right name. Functions are verbs, variables are nouns. The name you give a object should express what it is or does, no more and no less, and be readable in English (or whatever your spoken language is). If you add something to a function that doesn't fit the function's name, it either belongs in a different function or else you misnamed the function in the first place. This takes constant review of your code, from a literary point of view.
2) Rules are made to be broken. All great writers unhesitatingly break the rules in order to communicate more clearly.
Languages are for communicating, and computer languages are no different. Keep that in mind at all times, and you'll become a wizard.