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Comments are More Important than Code
CowboyRobot writes "I was going through some code from 2002, frustrated at the lack of comments, cursing the moron who put this spaghetti together, only to realize later that I was the moron who had written it.
An essay titled Comments Are More Important Than Code goes through the arguments that seem obvious only in hindsight - that 'self-documenting' code is good but not enough, that we should be able to write code based on good documentation, not the other way around, and that the thing that separates human-written code from computer-generated code is that our stuff is readable to future programmers.
But I go through this argument with my colleagues, who say that using short, descriptive variable names 'should' be enough as long as the code is well-organized.
Who's right?"
The canonical form of your maxim is "If you don't have time to do it right the first time, when will you find time to do it again?". The correlary is: "The problem with quick and dirty is that dirty remains long after quick is forgotten."
I want a new world. I think this one is broken.
Always comment. Always. I'm not a career coder, but I've done enough to know that if it's a project of any noticeable size at all, and you intend to read the code later, take the extra few seconds and COMMENT THE STUPID THING. It makes life a lot easier. The only thing that probably doesn't need commenting is a simple BAT file or a shell script. Comment!
i do a lot of code reviews at work and nothing makes me happier than good comments.
but just putting a bunch of blocks of comments that are like "get customer", "build record", etc are basically useless. If you use programming by intent then its more or less obvious that the code
GetCustomerFromDatabase(foo)
is going to do something with a database and get a customer. a comment telling me that is useless.
what i like to do is write a few paragraphs of text at the top of a function. it explains my general approach, why im doing certain things the way i am, why im not doing other things, and why the function even exists.
essentially the comments should be enough that anyone that knew the problem space ought to be able to read them and come up with more or less a similar implementation.
then, in the body of the method anytime i do something that i feel isn't completely obvious, i put a 1 or 2 liner infront of, i.e. "we have to do this because zergs are sensitive"
the end result of all of this is that code reviews can see what you were thinking at the time the code was written.. and you're documenting assumptions about the problem, the apis, your understanding of the language, etc, all right in the code. it makes finding errors pretty easy.. someone that can't even read source code can read the comments and get an idea of the correctness of your approach.
My opinions are my own, and do not necessarily represent those of my employer.
I agree. Giving your variables descriptive names is a good practice, but it's not nearly enough "commenting". If you have a piece of code that manipulates the values of those descriptive variables with bit masks to spit out a value, how is someone supposed to know what you just did? I think the adage "you don't document your code, but you code your document" is a little extreme, but it gets across the importance of code documentation. I'm working on an open source project of my own right now. I went back to modify a piece of code that I hadn't touched for nearly 4 months, only to make absolutely no sense of what the hell I was doing there. Luckly I commented it extremely well so after reading the comments I was able to get that "Oh yeah..." feeling and make the appropriate modifications without breaking the code. Lesson: commenting code may take you some more time now, but it's going to save you a hell of a lot of time later.
On that topic, what are some good examples of well-commented code? Rather than just see words, I'd rather see real-life applications of these practices. For starters, here's typically how much I comment my code: Allacrost source code (note: not all files were written by me, by I try to stress heavy commenting on the rest of my team)
Hero of Allacrost, a FOSS RPG for *NIX/*BSD/OS X/Win
hah I also grade as a university TA, and let me tell you what is more annoying than that... people who don't know how to indent their code, and want you to help debug it! Ahhhhh!!!!!
Boxing Equipment Reviews
Why on earth do we even have commenting? I mean, we went through the whole programming language concept precisely to make instructions to computers human-readable. Ideally, commenting should be obsolete - the language and its syntax should make it obvious what needs to be done.
If it turns out that after all that, our code still isn't intelligible, then isn't this some monumental failure of C, Java, BASIC and the rest, whose whole raison d'etre is to make weird things make sense?
If the comments are clear, a better programmer than you can come along later and say "What the hell was this guy doing?" and then replace your lines of fumbling crap with much cleaner/clearer code.
It's the difference between being able to see what you were trying to do vs. figuring out what you actually did.
Call it "Intent Oriented Programming" if you want.
Simple Machines in Higher Dimensions
Comments are a maintenence nightmare. They get out of sync with the code, and (especially when the code is bad to begin with) people read them instead of the code.
That means over time the human's understanding of what the program does starts to diverge from the computer's understanding.
This is not good.
If something is too hard to understand the way it is written without comments, it should be rewritten. You will save time in the long run, trust me.
Remember the old adage: Don't get suckered in by the comments--the bug is in the code.
--MarkusQ
I disagree. India has more engineers than the USA. And these are smart people. Some of them already know english, and others will have to learn. India is a country with too much poverty and so little oppertunity, that when a young kid is given a chance, he'll learn it all. They are lean (paid little) and hungry (willing to learn). In the USA, we expect $100 an hour to consult, one place I worked at hired an Arthur Anderson consulting team and the lead got over $300 an hour. I bet he would be *insulted* to have to work for $20 an hour. Are you going to tell me that the guy in India won't take that wage?
If it means people in India will have to learn english, they will learn english the same way they get their engineering degrees. They will study their asses off like their lives depend on it.
If people in the USA have half a chance, now is the time to take advantage of it and produce a better product than they do in India. Leverege every advantage we have, because the competition is getting better.
We could say how the Bush administration is screwing us, and to a large extent they are. We never should have let factories leave the USA to mexico. We never should have let outsourcing happen. I hope future presidents start raising the tariff, and force American companies back in the USA. But maybe we need to get a little more lean. It is hard for the avarage employee to give a fuck when you see the CEO get a bonus when he lays people off, or scum like enron managment steal the pensions of employees, but what other option do we have? Change the tax code to tax the wealthiest at a higher rate and pump that money back to the poor? Maybe raise the luxery tax rate? Increase the estate tax? Break monopolies?
Rosco: "If brains were gunpowder, Enos couldn't blow his nose."
The problem is usually functions that are too long and are not orthogonal. Write short, orthogonal functions and you'll see your need for heavy commenting go away along with the need for long variable names.
You need that comment?
if (kbd_input_rcvd)
{
process_input();
}
is not clear?
I think properly modularizing your code (breaking process_input() into its own function), and properly documenting the modules (defining good documentation of input, output, exception conditions, return values, side-effects) is more effective than writing verbose comments (like the one you've noted) in poorly segmented code.
This whole discussion is a bit short sighted. The better and clearer your code is, the fewer comments will be necessary. The more useful comments you add, the less time will be necessary parsing and understanding clear code. The better your design overall is, the less code reading overall will be required, because you'll have documentation outside of your code that explains how the system works, and where you need to go make changes. Saying one is more important than another is silly.
-Greg
Emacs will handle that too...
I actually agree with you though -- as long as the indent character in question is a tab. People who want to indent with spaces need their heads examined.
I want a new world. I think this one is broken.
Comments are essential to maintaining any project.
/**
...
//Holds temporary data
It's annoying when I go to the person who wrote a chunk of code fom a couple months ago to ask them some questions, they look at the code and have no idea why they were doing what they were doing.
I've always followed the philosphy that I should write and comment code so that someone who wasn't a programmer could read it and understand what was going on. This makes it very easy to go back even years and know exactly what the code was doing and why it was doing it.
But you need to write good comments and good code. I've actually seen this in code:
Gets an array.
@return An array.
*/
Array GetArray()
The other one I live seeing is data structures containing non-descriptive field names:
struct TmpData
{
int a;
int b;
float c;
};
Completely useless.
Good code and good comments makes everyone's life easier. I've seen a lot of good code, I'd like to see a lot more good comments as well.
~X~
~X~
Hello. I question. Look, if you need comments to explain the code flow because your method spans four screens and has six levels of conditionals in two levels of loops, all the comments in the world won't help you.
Especially if you change the code and now the comments are wrong
I have had the joy of maintaining lovingly commented code with all these huge blocks at the start showing what args get passed and what happens, and I can't understand a god damned thing about what it's doing, because the code all looks like All generalisms are wrong.
I am no longer wasting my time with slashdot
I found that writing the comments *first* my methods/functions is the way to go. This helps me organize my thoughts and makes finding where I should be refactoring much easier. After writing the comments, I fill in the code. By doing so, my comments focus more on the concepts and less on just restating what the code does.
Now with that out of the way, here's my philosophy on variable names... Every variable name should be as long as necessary to describe what the variable is. Having said that, the shorter, the better. If you have a lot of long variable names, then you probably have not found the most elegant solution to your problem.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
You know whose fault that is? The morons that mark you down if you don't comment trivial programs like Hello World.
I actually ended up doing three introductory programming courses at college and university (overlap in curricula), and I've been marked down for not including this type of comment in all three courses.
The problem is that they try and teach you to write comments prematurely. When all most people on the course can write are programs like Hello World, they really can't see the use of comments and there are no good examples to give. The use of comments should come after things like functions etc IMHO, so that students can actually see how comments can be useful.
I find that for simple code that requires little thought, little in the way of comments is required. Sometimes comments just get in the way as the code progresses over time, and the comments don't. It's better to code with long descriptive variable names, and structures then depend on comments.
//Customer ID structure // ID number for the customer // Agent Name // Customer Name
For example which would you rather read.
#define AgentNameLen 41
#define CustomerNameLen 51
struct CustomerID
{
int CustomerID;
char AgentName[AgentNameLen];
char CustomerName[CustomerNameLen];
};
or
struct CoID
{
int ID;
char AName[41];
char CName[51];
};
To me the first is much more clear, and throughout the code will be obvious as to it's use. The second is mildly clear, but will degrade as new things get added to the structure.
The first also allows things like
for(int i=0;iAgentNameLen;i++)
which makes it very clear that you are iterating throught the agent name.
Algorithm's should be documented, as much as possible, at the top of the function, and any function that takes more then a screen should be looked at to see if it can be broken up into smaller functions.
(Almost) Always code towards maintainability, never speed. Usually it pays off within the year.
So to sum up. In order of importance:
80% code clearly with an eye towards maintainablity
20% comment
Sooner or later, not documenting properly will bite them in the ass.
Actually I have found that more often than not, not documenting properly only bites someone else in the ass.
This is likely the source of the problem, and the least likely to change. I suppose it could be part of the QA process to check for notation on code, but I somehow suspect that with programming jobs on a one way trip to Bangalore that readability it secondary to "works cheap."
~Rebecca
The code needs to be well documented, where "well" means both "correctly" and "frequently." Lots and lots of poor documentation is just as bad as little or no documentation. And documentation, no matter how well done, will not fix lousy code.
So I don't question. The story poster is correct. Code needs to be well documented, and neither good organization nor descriptive variable names is a sufficient replacement for documentation. But you're absolutely correct too that documentation is only a small part of what it takes to write good code.
"The legitimate powers of government extend only to such acts as are injurious to others." Thomas Jefferson.
If you don't put in the necessary time [...] to properly document your code, you'll wind up spending a lot of time trying to figure out just what you did and why
The corollary to this is the need to maintain existing comments when the code is changed. Misleading/outdated comments can sometimes be worse than none at all.
proper documentation is professional courtesy
I couldn't agree more. Good documentation gives you context and insight into the motivation of a past developer, which can be priceless when trying to understand unfamiliar code. Good variable names can give you the "how" the code is implemented, but good comments give you the "why".
What do you mean "some of them already know english"??
Most indian graduates already know english, if not almost all of them!?
I guess it makes us feel safer if we come up with more reasons for another culture's inferiority?
PS: I am not indian..
Blockquoth the AC:
That was modded (+1, Funny), but I think it was a serious comment. It wasn't a bad rule of thumb, either.
If you disagree, post your argument. (-1, Overrated) isn't your personal censorship tool for views you don't like.
There are three things the poor maintainance programmer who has to maintain your code needs to know: The What, the Why, and the How.
The What: What is this code trying to do. This is where your design documents come in, as they tell what the overall goal of the program is.
The Why: Why are you doing what you are doing? Why are you writing to this hardware register twice? Why do you divide this value by 1800 here? This is where comments are needed - to explain that the hardware sometimes doesn't take the value on the read, or that the nominal deviation of this signal is 1800 Hz.
The How: How are you getting the work done. This is where well written code with well chosen variable names comes in.
www.eFax.com are spammers
Out of date comments are far far worse than none, and this happens with absolute certainty.
People will usually update variable names, but they won't update comments, especially when the IDE makes comments a different colour - your eyes don't even see them after a while.
You think spaghetti code is bad with no comments - try it with misleading comments.
Servlet v2.4 container in a single 161KB jar file ? Try Winstone
..and try to remember what I was thinking when I wrote the code
People sometimes forget that you are not only documenting WHAT the code is doing, but WHY you are doing it that way. You can usually figure out the what from the code itself, but trying to figure out the why can be next to impossible.
I wrote some code years ago to calculate (Australian) Capital Gains Tax liabilities. I knew it would be a hassle to update the code when the tax laws were inevitably reviewed and updated, so I went out of my way to put notes about EVERYTHING into the source code. Where I would normally have put in a short quip, I put in a longer descriptive comment.
Five years later when changes had to go in, it took me an hour or two to get back up to speed with how the program worked, but without that extra documentation it would have taken far longer and I would more likely have broken it when trying to patch it.
Ho! Haha! Guard! Turn! Parry! Dodge! Spin! Ha! Thrust!
I kid you not, this is real code my supervisor writes.
Note that this is matlab code, where commas are both an end-of-statement indicator (it's also possible to use just a semicolon), and an array index separator. The nice thing about this code, is that I can at least guess where most of the variable names come from. Oh, and there was *no* line break in the original code. Hooray for the avoidance of those wasteful '/n' characters?!?!
To answer the original poster: yes, comments are of vital importance.
Then again, if a program is structured right, things can be organized into sections, each of which is then commented, as opposed to a bunch of seemingly random lines with comments spaced throughout. Sometimes the layout of code, in conjunction with good variable names, is the best possible method of commenting it. The one thing comments are good for is to assure that someone not familiar with the particular language being used, will still understand the purpose of the code.
Well, that assumes that you have a nice, clear set of steps (like the example above). However, if you have a series of very complicated, non-intuitive steps that MUST be done, then commenting is pretty much essential.
XML is like violence. If it doesn't solve the problem, use more.
Don't forget about students who use assert()'s for validating user input!
Insightful: 76, Off-Topic: 379, Flamebait: 24, Funny: 152, Interesting: 201, Underrated: 55, Troll: 9, Total: 896
I think that BOTH the comments and the code need to be readable. I've seen code with lots of great descriptive comments, but when you look at the actual code you can't tell if it does what the comments say it's supposed to do. The same holds true for the reverse. I've see code that's well structed, readable, descriptive variable names, etc. But without some comments about how all the pieces fit together the code can still be confusing.
I actually agree with you though -- as long as the indent character in question is a tab. People who want to indent with spaces need their heads examined.
There's no solution to the indention problem. You'd think simply mandating tabs would work, because that way everyone can set the tabstops to whatever they want, but in practice it doesn't work. People don't setup their editors the same way. Some have "tab indents with tab", which would be the correct choice, but other have "tab indents with spaces". Then you have those that refuse to use tab at all, or decide to use spaces to align certain blocks, and so you get a mix of tabs and spaces in a line. The line looks right with tabstop=4, but looks like crap with the default tabstop of 8. This assumes people don't untabify on open and save. That replaces all tab characters with spaces.
In practice, a file that is touched by enough people will end up having every line indented to some screwy level with nothing lining up correctly. I know. I've seen it.
The problem with comments is there is no constraint to keep them...
Code Reviews help, but not enough.
There is a better way. It is called Test Driven Development. Tests are the least ambiguous, most correct and current commentary on the code. They are also always at the correct (higher) semantic level than just paraphrasing the code.
Given a choice of reading comments or reading well structured tests, I will read tests any day. I at least know if they run, that they are true.
Google knows.
>People who want to indent with spaces need their heads examined.
speak for yourself. I know my 4-space indents will be the same regardless of whatever editor and/or settings are used. and I won't get warnings about the tab character from my f90 compiler.
That's not true. One line comments won't help, but a large descriptive comments will. If you can explain the code by talking about it, then you can explain the code by writing about it.
Especially if you change the code and now the comments are wrong
You're incompetent if you don't change the comments to match the code. You're equally incompetent if you come across incorrect comments and leave them in. You're supposed to the job, so do it.
I have had the joy of maintaining lovingly commented code with all these huge blocks at the start showing what args get passed and what happens, and I can't understand a god damned thing about what it's doing, because the code all looks like
As Fred Brooks said, "There is no silver bullet." Clearly written code can't replace comments. Clearly written comments can't replace poorly written code.
1. Comment each function
- Function name
- what it does
- parameters
parameter name - what is is for and any restrictions on it (i.e., must not be null)
- return value (all possible return values)
2. Add comments to each file you modify so that over time, the file becomes better documented
3. Add ASSERT() like comments and ASSERT() or equivalent to your code
4. Use dividing comments like a line of dashes to seperate blocks of code
5. Put in a '?' comment for code that you do not understand (good for function headers)
6. Avoid stupid naming schemes for your local variables since that makes it harder to comment
7. Review your code for both logic and comment completeness after you code it before committing it to version control
8. Tag your bug fixes, code enhancements with a comment followed by a dash, date, and your initials. This is essential for large projects or for anything you will be working on for more than 6 months.
9. Format your comments so that multiple line comments line up on the left hand side (increases readability)
10. Don't count on java doc or equivalent as being good enough code documentation.
Ive been in enough classes this year (well below my level.. dammit, I need the "letters") that Ive come to the conclusion that introductory programming courses are taught all wrong.
Write 5 lines. Write 20 lines. Write 100 lines. Of useless and pointless code.
What should be done is: Take this 1000 line programme. Add on 5 lines. Add on 20 lines. Add on 100 lines. Beacuse that would require being able to read code, too. Being able to understand what is already there is frequently more then half the battle. Saying "What the fuck does this mean?" a few dozen times is the only way to get to write comments. Being a sysadmin, rather then a full time programmer, this took me litteraly years to learn. And it was usualy "What the fuck were you doing here, brain? Dammit, one of these days were going to have to start commenting our code."
About 6 months ago, I read through a project request on one of these ebay-for-coders sites. Language optional; 1 comment per 5 LOC, but if using Perl, 1 comment per 2 LOC.. With requrements like that you are only asking to get BS comments like "Print X to the console".
There's also something as far as too much commenting. Don't get me wrong, I can't stand uncommented code. I learnt, like most people, the hard way -- go back to edit something I did 6 months ago, and have no idea what's happening.
But I don't think this is useful:
Here's my version of your same sectionThis isn't really the greatest example, but I like to comment sections of code. The details can be read by looking through the code, with "hints" as needed (for example, reminding me that SDL_GetTicks() is the current time).
Well commented blocks mean you can skim through the code, getting a quick overview of what's happening, without having to read in much detail.You don't have to care about the details of the look, you just know by the time you hit the } you've found what you wanted.
Don't take this personally or anything. Your code is very readable.. there's just lots of extra comments (granted, I've seen worse) that are really just not worth putting in.
(also, proper indenting is as, if not more, important.. of course,
Speak before you think
The problem is that they try and teach you to write comments prematurely.
No, the problem is that they try and teach you to write code prematurely.
Document your application, requirements, constraints, and system interactions (what the engineer does). Then write the code (what the coder does).
What you will quickly learn is that it's better to be the engineer than the coder. What you'll realize is that the engineer is the client-side guy that figures out how to solve the challenge presented and the coder is the guy who can live in Manipal.
The computer scientist is another guy altogether, that sets the boundaries within which the engineer must work and provides many of the tools.
Somehow CS education has gotten horribly derailed, and asks students to combine the equivalents of electromagnetic theory, power system design, and basic home wiring in one curriculum. No wonder enrollments are plummeting - nobody knows what a CS major is or should do.
If it was hard to write, it should be hard to read.
Steve's Computer Service, Hobbs, NM
I'm a CS grad student, and the stuff I see from my fellow grad students amazes me. A pretty large percentage of our incoming students are from India, and it's obvious that a lot of them have never written any significant amount of code. (From talking to a few of them, I get the distinct impression that the indian educational system is pretty much memorize-and-regurgitate all the way up).
In one case one of my fellow grad students was working on a fairly trivial assignment - Take the results of a web form and email them somewhere. (Yeah, in a grad level class. What a joke.). This was done in Perl, and he was having trouble getting it working. So he asked me to look at his code.
No indentation. Sometimes two or three statements on a line. Random line spacing. No Comments. No use strict. No use warnings. No variable declarations whatsoever. Variable names like $a, $b, etc. Moreover, he'd turned what is about a 10 line Perl script into a good solid 50+ lines of code. Augh!!
Why?
In assembly, this is totally necessary. For example, this old DOS code
Obviously, without the comments, you won't understand what I wanted to do, and you could for example suppose that I could have replaced 'mov bl,7' by 'mov bl,ah' since they were identical, which was pure coincidence.
In higher level code, on tree-walking functions, or in finite state machines, you need to comment your intent, because you'll always put bugs, and the only thing which counts is the algorithm that you validated by hand on paper. So you explain what you tried to do, and anybody reading your code (including you) will then understand why some transitions don't work as expected.
I often ask friends to comment their interfaces so that even themselves know if their input is valid. Example below:
But on the other end, I hate useless comments such as all cited in other posts (eg: print "x" on console). They make it difficult to read code.
Following such rules will generally help people understand your code, and help yourself maintaining it over the years. That's also one reason I quickly forgotten how to code in perl
Willy
You could continue along these lines, and get to a point where it would be obvious what the code does. The comment in that snippet also addressed "why", in addition to "how". I would move the "why" explanation into a document that defines the protocol.
Karma: -2147483648 (Mostly affected by integer overflow)
Comments are important. However there are different types of comments each with varying degrees of priority. Comments are primarily code documentation. Code generally starts with some sort of design and design documents are the first stage of code documentation.
Designs don't have to be monolithic war and peace style documents, rather very high level documents describing the purpose of the code. This generally gives future maintainers of developers an idea of the effect changing the code will have on an application.
Class Documentation / API Documentation / Java Docs / Perl Docs / .Net XML Docs are in my opinion are the most important forms of code documentation. I very much enjoy reading articles about programming concepts and designs. But when I am coding, it is the API documentation that I spend most of the time reading. My favorite languages are those which provide a large library of useful classes that I can reuse. perl, php and Java have large online communities that produce reusable library. This has two effects.
Writing such small reusable libraries generally the documentation will be very good. Each reusable library has documentation that allows other programmers to figure out how to use them. This means people writing these libraries are not only good at writing reusable code. They are also good at instructing others about how to use such code. Over time they become experts at documentation and serve as role models for others developer. .Net is an example of a large development group accepting these practices and now trying to embrace such strategies. But there is a much more interesting aspect to this.
Developers using these libraries become very good at using libraries. As programmers become more experienced, they progressively become more adept at finding reusable code and being able to make it part of a consistent unified solution. Developers who are practicing these techniques are becoming very good at designing and documenting reusable code. Having this community of code exposes developers to an enormous amount of high quality well documented code. This not only allows them to be more efficient developers, but teaches them to be very efficient designers. These are the people who become the respected technical leaders and in the optimistic case your boss or the senior programmers on the projects for your work. Perhaps you are one of those programmers and other a benefiting from your use of such tactics.
The least import type of code comments are the one or two lines before the while loop. These types of comments document the code at a micro level. At this level you rarely need a lot of comments. In most cases a competent developer requires the ability to decompose the code and this level without a lot of comments. This type of comment is never the less on the forefront of most discussion about code comments. Less experienced developers general can figure out the code is difficult to maintain but may not know exactly why. Not having the experience to point at exactly what makes the code difficult to maintain they assume it lacks sufficient documentation. This argument seems almost immediately logical. Unfortunately there is a flaw in this logic.
Just because code is difficult to maintain or enhance does not indicate poor documentation. I have maintained lots of well documented code that required hundreds of hours of modification to fix simple bugs or implement small changes. Several years ago I was asked by my company to help when a new application was released to our clients. This code met the acceptable requirements for code documentation. Each file had a header with modification history including date and developer information. Comments we also placed liberally throughout the code. This projected resulted in a single release and is currently being rewritten from the ground up. When I was asked to assist with the analysis the code documentation helped us quickly conclude the application would not be a viable replac
I think it's safe to say comments are for the benefit of those who have not assimilated their language, their APIs, etc. Sure, documenting interfaces is essential as well as how certain data structures are used. Most of the other comments I have seen are completely superfluous and only enhance the understanding of the uninitiated.
cat
Never tell me you are adding shifting the varaible by 4 bits, instead tell me, you are converting from bytes to 16 byte blocks due to a chunks size conversion because that's the size the output device expects blocks to be written in.
Don't tell me you are swapping variables, tell me why the values should be exchanged.
Don't tell me you searching for the max value, tell me what the max value is used for when you find it. That sort of concept.
One easy way to do that, is to look at code and the comments. If the code and the comments could get out of sync because you changed the implementation, the comment is wrong. You documented the how not the what.
There are cases where the how is important, especially when there are things where the "how" doesn't behave naturally. Oh, this sorts numbers, but it is intentionally sorting the ASCII values of the numbers when represented as a string. That'd be very useful to know. I'd expect a sort to work based on the binary values.
The other rule I remember from code complete, and from "Writting Solid Code", was the concept of laying out the pseudo code that explained what you wanted to do at a high level. Then filling in between the comments with the implementation. It was a very good way to end up with documented code.
Kirby
I'd say you're right, comments are more important. Clearly-written code should make how it's doing things obvious, yes. Comments, though, should say what is being done and why it's being done the way it is.
1) production code is not a tutorial of the C(++) language. It's okay to assume the reader knows their stuff. A bad example:2) production code is not documentation on the APIs that it uses. APIs have their own documentation, the reader either is familiar with it, or can find documentation. A bad example:If the API is only used in one file, then you could point at the documentation right where the header is included. If it's used on a project level, then it should be pointed to at the project documentation.
3) comments are just as much about why you didn't do something a certain way as it is about why you did do something a certain way.
4) the obvious; name your variables correctly. Instead of:use5) if you are implementing using a spec, somewhere in the top of the file describe the revision of the spec. Additional comments can describe the section of the spec that they relate to.
For example:6) NEVER put actual values in comments. For example:The code already shows the actual value, and all too often the comment doesn't get updated.
Sometimes it's okay to list the possible values:but I only prefer that when this is the _only_ place where it is used. Otherwise you'd use enums and/or refer to the documentation section/page
7) write top level documentation to explain what the software is actually supposed to do. It's amazing how often this is missing. Write one bloody page that describes to a programmer that doesn't know ANYTHING about the software what the hell it's supposed to do, and how it's accomplishing this. It also helps tremendously if every file has a little description in the header. And I'm not talking about what license the code is distributed under.
Good code is code that's modularized into so many properly-named, small functions, that it looks like the pseudocode originally used to describe the algorithm in the first place.
Still, if you're implementing some arcane algorithm that isn't documented very well in academia, let alone taught in most universities, and is full of obscure mathematica that even mathematics doctorates will have to squint at, then be a dear and just comment the fucking code to help make it easier for your colleagues to comprehend. If you can implement something so fancy and grandiose that it can have its own patent, certainly you can spend 5 minutes to clarify the principles behind it in documentation as well as sources. It isn't hard.
Slashdot requires you to wait longer between hitting 'reply' and submitting a comment.
You cannot read code before you can write code. Your idea should be the 4th step. Let them do the basics, and then learn to mess with something intermediate. After all, that many lines of code is going to be intimidating to someone not intending to go past that level of the course.
Actually, it's a very usefull comment. The comment is not incorrect, the code is, and when you're later trying to make the code correct, the comment shows exactly what the code should have been.
:-)
If only all mistakes were that well commented
Yes, it's worthless and childish. What would have been better? This:
numberOfApples=5;
numberOfOranges=2;
print(numberOfApples+numberOfOranges);
If code is well-written and uses good abstractions, good variable and function names, and short functions, it needs far fewer comments and is more understandable.
"To be absolutely certain about something, one must know everything or nothing about it." -- Olin Miller
Don't forget about students who use assert()'s for validating user input!
It is not the best way to validate user input, but it is better than no validation.
Do you care about the security of your wireless mouse?
The three items you seem to object to all have fairly legitimate uses in some computing contexts.
1. Comment each function
- Function name
Why do you need to repeat the name of the function? It's right there in the code.
Yes, and in some contexts that is precisely the problem. Depending on the language and editor(s) you are using, embedding the function names in comments can be very useful.
For example, if I use an "FC" command in a Unisys 2200 mainframe editor (say ED or UEDIT) to show all lines starting with "C" (comment lines) in a Fortran program, the results will be confusing if the function names themselves are not specified in a comment line. All I will see is comments with no context.
By adding the subroutine or function names in the related comments themselves, that missing context is restored.
5. Put in a '?' comment for code that you do not understand (good for function headers)
Code with personal annotations should never be released.
While I agree with this part,
If you don't understand it, you shouldn't be working with it; go find someone who does understand it instead, or stop and work it out.
this part of your comment seems limited to "perfect world" scenarios only.
I've spent most of my career working on mainframe code that was either originally written by people at other organizations or companies, or that was written so long ago that the original designers and coders were either retired or deceased.
When making a first pass at understanding such code, I've found it to be quite useful to leave various comments in the code so I have a good idea about my level of understanding the next time I have to come into that area of code.
I've also found such comments useful when left in the code by others, since it reflects their level of understanding as well. Some of the stuff I'm looking at now was originally coded in the early 80's and rewritten by my predecessor, and the comments he's placed in the code have proven to be invaluable to me, even though some of them were speculative in nature. Something like "What does this code do?" in his comments often alerts me to a tricky part in the logic that I'll want to pay special attention to.
FWIW, question marks and other comments/speculations are commonly used when working on someone else's previously-written code, at least in my experience, especially when that code is only intended for use in-house (the source is not released to customers).
8. Tag your bug fixes, code enhancements with a comment followed by a dash, date, and your initials. This is essential for large projects or for anything you will be working on for more than 6 months.
Once again, nothing with personal annotations should ever be released into source control. Not only should I not need to know who wrote or changed a particular snippet of code to fix a bug, I shouldn't even be able to tell by looking at the code.
When working on code that was written in-house, and which is intended to stay in-house, I *want* to know who made a certain change and why it was done. That type of notation can save me (or another support programmer) a lot of time.
While those types of details might be handled by the source control system(s) that you work with, keep in mind that some of us work on platforms where analogs to the UNIX-like source control systems many people are used to simply do not exist (and often such a thing isn't really needed).
When I did Unisys A-series mainframe contract work at a small company in southern Minnesota, they used the unparsed end of each COBOL line as a comment area, and one always placed their initials and a date there so people knew who did which changes and when those changes were created. The editor they used (CANDE) even had a special setting to automagically place a change mark on the end of each line that was modified.
A si
Mainframe/UNIX Bit Twiddler and long time Windows/Linux Hobbyist.
The Theorem Theorem: If If, Then Then.
This is a good example of code that can be improved for documentation and readability, actually. Instead of checking for negatives, which is backwards to normal thinking, you can assume a combination will not work, and then describe the combos that will work:
/* Ensure arguments are valid */
/* make sure argument order matches the order
/* loop through each potion combination */
/* check that the potion combi is filled in
/* check if this combination matches the
/* this combination works. Use its
/* make sure we're not returning junk */
Most of your code would look like this then:
PotionCombo potionCombos[] = {
{ WATER, SOIL, MUD }
{ WATER, BEER, CHEAP_BEER }
};
A comparatively small loop function can check the list:
/* checkPotionCombo
Check a given combination of potions,
returning the potion that results.
Returns: the combined potion, or an empty
flask if the mixture is invalid.
*/
function checkPotionCombo(Potion a, Potion b) {
REQUIRE(isValidPotion(a));
REQUIRE(isValidPotion(b));
Potion result = EMPTY_FLASK;
of our combination lists (lower potion
number first) */
a = min(a,b);
b = max(a,b);
for (i=0; i<NUM_POTION_COMBOS; ++i) {
properly */
assert(isValidPotion(potionCombos[i].a));
assert(isValidPotion(potionCombos[i].b));
assert(isValidPotion(potionCombos[i].result));
arguments
*/
if ((potionCombos[i].a == a)
&& (potionCombos[i].b == b)) {
result, and stop searching */
result = potionCombos[i].result;
break;
}
}
ENSURE(isValidPotion(result));
return result;
}