> there are absolutely times when comments are necessary.
I'll have to take your word for it, because I've yet to run into that situation.
I'll have to take your word for it, because I've yet to run into that situation.
Comments are for why.
Sometimes the why is obvious, then you don't need a comment. The rest of the time, add that comment. Even if it's something like "Steve in accounting asked me to put this in."
It's generally true that the code expresses the what, but it's also true that it can take the reader time to discern. A simple comment here and there can be a shortcut to this discernment which, over thousands of lines of code can save serious time.
And when you change the line because Tom asked you to change it again - you don't need to remember to remove the comment about Steve.
I have recently started working on an existing project which is all new to me. Having to go through git commits looking for relevant comments is just a silly suggestion. Its far more useful when I am browsing through the code, trying to understand it, to see a comment beside the relevant piece of code, not hidden away in git commit messages.
IMHO comments aren't there for newcomers. You are a newcomer for a month or 2. You are a developer for years most often. Besides, how is
//Steve in accounting asked me to put this in
foobifyTheBaz(bazPtr, foobificationParams);
foobifyTheBaz(bazPtr, foobificationParams);
And you don't look for git commits. You enable git blame annotations in your IDE and hover over the relevant lines to immediately know who, when, and why changed that particular line. That's why commit messages are as important as good naming IMHO.
By the way, when you have code like:
//Steve in accounting asked me to put this in
foobifyTheBaz(bazPtr, foobificationParams);
barifyTheBaz(bazPtr, barificationParams);
if (mu(bazPtr)) {
rebazifyTheBaz(bazPtr);
}
Unless they're something like "fixed indentation".
// We foobify the baz in order to ensure that both
// sides of the transaction have their grinks froddled.
// This was a request from Steve in Accounting;
// see issue #4125 for more details.
I strongly approve of putting relevant info in your VCS commits too, of course. But, e.g., if someone changes the indentation around there then your git blame will show only the most recent change, which isn't the one you want, whereas the comment will hopefully survive intact.
I envountered it a few times and it was never a big problem.
The problem with comments in the code is - they have to be maintained "by hand", and they are often separated from the context after a few independent changes.
When you change a function called inside the foobify function because of another change request you will most probably forget to check all the calling places all the way up the callstack and fix the comments refering to foobify function. And then comments may start to lie.
I encountered lying comments a few times and it usually is a big problem. I started to ignore comments when debugging, and I'm not the only programmer that I know that does that.
I do think there is a place for comments in the code, for example for documentation of some API, but IMHO commit messages are the perfect place for explaining reasons of particular change, and I prefer not to repeat that.
Which way does the returned force vector point? Towards mass A, or towards mass B?
2) Vector3 UnitVectorWithDirection(Vector3 originalVector);
What does this function do when the magnitude (length) of originalVector is zero?
3) float ArcTan(float x);
What is the allowable range of values for x?
...
1) Vector3 calcNewtonianGravityToB(float massA, Vector3 positionA, float massB, Vector3 positionB);
2) Vector3 unitVectorWithDirection(Vector3 originalVector_mayBeZero); vs. Vector3 unitVectorWithDirection(Vector3 originalVector_throwsIfZero); (if in a supporting language, throws declaration would also clarify).
3) float ArcTan(float x_throwsIfZero); or float ArcTan(float x_returnsNaNIfNot0to1), etc.
This assumes:
(a) You're not working in a language or environment that supports range constraints in the first place, cause if you are then that's ideal.
(b) You're working on personal code or a small team. If you're writing code for public consumption you have no choice but to add detailed API documentation if you want to be successful, even if it's not DRY.
Certainly calling things like "x_returnsNaNIfNot0to1" works, but I find it a bit ugly and it gets complicated if you have multiple or more complex constraints.
This is where languages with docstrings are nice. In Python all I would do is add a """ comment describing the inputs and the return values.
You then have a) a comment describing the code; and b) documentation that's standard so people can pull it up with pydoc or ? in Ipython. When I'm working in Jupyter, I often hit shift-tab to check what a function is expecting.
For one, handling rotation sign (is positive clockwise or counter-clockwise), left-handed vs. right-handed coordinates, etc. through c++ template parameters.
Ideally, you'd have some tests as well that would test those kind of corner-cases and illustrate failure cases and expected outputs.
Sometimes comments are just to save future you some time or help other developers find context.
Suffice to say any project of significant complexity will probably require comments at some point. That complexity can come from the code, the task, the stakeholders or the dependencies.
Unless you are happy with a method name like getSimpleProductInstanceThroughCoreFactoryBecause ModuleRewriteWillBreakCompatibilityWithSecurity PatchSUPEE5523 ()
In that case I guess you're right.
Edited to stop the method name stretching HN layout.
There were no fixes performed in the method, the method just gets a product instance from a factory. The comment gives reasons for why it was using a core factory directly instead of using the automatic object resolution mechamisms.
The real method name was getProductInstanceFromCoreFactory. Still long, still clear as to what it is doing. But making the context clear would be more code than it is worth.
Avoiding comments by writing clearer code isn't a bad habit, but my point is that they are very useful to provide context for something that getting context for would otherwise be erroneous or cumbersome to implement.
> It's usually something simple like, "This cast avoids a special case in method X", or along those lines.
If I had an issue like that, I'd fix method X to be more accepting of unclean inputs.
For the rest of it, I try to write as cleanly as possible, and as robustly as possible the first time, so I'm not in the dark the next time I have to look at it. If I have to take time out to re-understand how it works, I'll just take the time and not feel guilty about it. The company wanted me to use that dreck, I'm not going to feel bad about having to take more time with it.
I don't think comments would help much in the second situation given decent engineering the first time around. If it's my code, I'll usually recall the idiocy I had to work around when running down whatever issue had me looking at it again.
Also, again perhaps because I use Ruby, it never takes me more than a few seconds to name something. If it does, then it's a code smell and I go looking for the missing class.
Example for obvious: Int add(Int x, Int y) in a typed language. Example for not obvious: add(x, y) in an untyped (or "dynamically typed") language (Does it auto-coerce? How? Can it add complex numbers? In my particular representation? ...).
Someone mentioned that sometimes comments are useful e.g. to document a quirk/bug in library function you call, and I have some examples of that in my own code. But most often you should be able to rectify that by wrapping said function in your own one that omits the problem.
If a function seems impossible to give it a sensible name that isn't ridiculously long, split it up. The more clear code of the individual parts and how they are combined should give a hint of what is actually computed here. Maybe it's a new concept in your business logic, in which case providing a clear and exact definition makes sense anyway (put it into the appropriate place in your documentation). This whole procedure can take a significant amount of time, but it will be worth it in maintainance!
That's precisely why you don't optimize. If you find you need fast code, you use a different language. Ruby is the language you use when maintainability and extendability take priority over speed. It's excellent for web development, where any speed improvements you make will ultimately be dwarfed by network latency.
> Example for obvious: Int add(Int x, Int y) in a typed language. Example for not obvious: add(x, y) in an untyped (or "dynamically typed") language (Does it auto-coerce? How? Can it add complex numbers? In my particular representation? ...).
That's a good observation, and it's made me think about how I deal with this in Ruby. First, generally you can tell by looking at a method's code what it's expecting you to pass to it.
Second, you don't generally pass around complex types to library functions, you use basic Ruby value objects like strings, symbols, hashes, and arrays. A gem will often define its own classes, which you might pass objects of around, (money, phone numbers) these will often be the primary focus of the gem, and how to use these objects will be written right there in the documentation. These classes will typically have "parse" functions that will take random input and turn it into a more useful object.
In Ruby, you generally only pass around complex objects in your own code, using JSON or some other format to interact with external systems
Ah, now I get you :)
> First, generally you can tell by looking at a method's code what it's expecting you to pass to it.
Here we might differ, I would always prefer to state clearly in the function doc what types of parameter values are allowed. For example, even if you have a really simple little wrapper in javascript:
function log(x) {console.log(x);}
/**
* Logs x to console.
* @param x a value of a primitive type (other types are not guaranteed to be logged in a readable manner).
*/
function log(x) {console.log(x);}
Yes exactly, it will be documented as any public API should be. I have no problems using opaque types. But a function call(x) which expects x to be some object representation and not any old string (for which the library has constructors, e.g. PhoneNumber(string)) should surely document this, no?
I can't tell you how many times I've been reading a comment that runs quite contrary to what the code really does. You then end up reading the code to reason about it anyway, paying two taxes. After too many of those experiences, you just end up going straight to the code as the source of ground-truth.
This all depends on the readability of the code / and how soon these comments get out of sync. Maybe my experience is atypical, but I doubt it.
I certainly am.
This way, I can run git blame (or the equivalent VCS command) on the file and get a reasonable set of comments that usually match up with the code.