[arethuza]

I tend to get a bit upset if code has comments that basically just describe what code is doing rather than why. Stuff along the lines of:

   // Increment the total
   total++;
   // Execute our SQL query 
   var result = query.execute();

Seems to happen a lot with developers who use comments to "sketch out" code (not a bad thing) and then leave the comments in place when the actual code is written.

[MattSayar]

That's a technique Steve McConnell calls "The Pseudocode Programming Process," and while it's verbose, it's not a Bad Thing. I don't do it, but I'd rather have comments like you posted than none at all.

[reddit_clone]

That is legit. I have done it on occasion. It is like a relaxed form of literate programming.

I don't understand this vitriol against all forms of code commenting. (I personally hate the useless, mostly empty function headers forced by some coding standard)

[einhverfr]

The problem has to do with maintaining large, complex, and frequently changing projects. If your code tells me what the program is doing the first thing I have to do when debugging is ignore the comments.

If the comments describe the code this means I have to ignore all comments including those which may be relevant to my debugging. This causes a few specific problems in a collaborative environment.

The first is that the comments get stale/out-of-date/etc, more quickly and are therefore consigned to the archaeology of the program rather than of current relevance. At least with spurious logging, I can take it as a sign that someone had trouble with the code here. With comments I cant even tell if it was done in pseudocode and then translated below. It is useless.

The second is that you can't just add relevant comments into the mess without deleting all the other comments first. Otherwise they can't be sorted out easily or efficiently. In other words, it is worse than useless because it keeps proper, useful comments from being seen or read.

Third, if there are relevant comments there, such as

# This is the maximum value the standard allows for.

Then I won't see these and I am more likely to miss them and hence screw something up by accident.

A better approach is to recognize two things:

1) The code itself needs to be so clear, that you never need any comments for debugging (interface documentation is something very different), and

2) The code plus the documentation together has to be easily readable to the programmer. It also needs to be clear, concise, and avoid duplicating messages any more than needed. Duplication with the documentation of course is required by definition.

I hear a lot of people say they have code they would like to release open source but don't want anyone to see how horrible the code is. The answer is to learn to write code with a dual audience --- human and computer --- in mind. The code comments then function like footnotes would in a text, or as a way for two or three programmers to discuss/debate differences in approach. However, they are not debugging aids.

[gnaritas]

Actually many of us do find it a bad thing. Useless comments are worse than no comments.

[MattSayar]

sed 's/\/\/.*//g' shittyComments.c

[theorique]

you can get even crazier if you add in plenty of spurious logging

# print out the value of x prior to increment print("x value prior to increment: %d" % x)

# increment the value of x x += 1

# print out the value of x after increment by one print("x value after increment by one: %d" % x)

[arethuza]

I've seen quite a lot of code that kind of looks like this:

   // Increment the total
   log.Debug("total before increment=" + total);
   total++;
   log.Debug("total after increment=" + total);
   

I find myself looking at it and going where is stuff actually happening!

I sort of wish someone would allow comments and logging to be combined as language features.

[throwaway-864]

Check out Smart::Comments module in Perl [1].

It allows the specially-formatted comments to produce debugging output.

From the synopsis:

    use Smart::Comments;
     
    my $var = suspect_value();
     
    ### $var
     
    ### got: $var
     
    ### Now computing value...
     
    # and when looping:
     
    for my $big_num (@big_nums) {  ### Factoring...      done
        factor($big_num);
    }
     
    while ($error > $tolerance) {  ### Refining--->      done
        refine_approximation()
    }
     
    for (my $i=0; $i<$MAX_INT; $i++) {   ### Working===[%]     done
        do_something_expensive_with($i);
    }

[1] https://metacpan.org/module/Smart::Comments

[einhverfr]

Noooooo..... Not magic comments.............

Magic comments are evil, the pox of the earth, etc. I have nothing good to say about comments as code. This totally messes up the separation between code and comment.

[einhverfr]

The typical case where this happens is that the logging was added because of some bug somewhere and this was put in place to figure out what was going on with total. See it as an archaeological record more than anything else ;-)

[theorique]

Hm, my code didn't format as intended. What you wrote is what I meant.

[flatline3]

I prefer code where I can skim the comments and see the major plot points, at a glance.

[dllthomas]

If you need to skim the comments to see how a function is doing what it's doing, the function is too long.

[barrkel]

Maybe the compiler needs to see the whole function in order to properly optimize register usage, because the function is on the critical path.

There is sometimes more to code than readability, unfortunately. I have worked with functions thousands of lines long that can't be broken up without losing a few percentage points of speed - but these functions are called millions of times.

[dllthomas]

It's always a matter of heuristics, for sure. When you need to modify code in a way that's less than readable/obvious, then you start dropping in comments to compensate. Your first pass should be understandable and obvious and readable, with comments typically restricted to documenting functions and interfaces.

[LiveTheDream]

Effective use of macros or inlining could solve that problem.

[barrkel]

Over 2,000 lines with macros. Inlining didn't give good enough results (at the time).

[flatline3]

When it can take 3-4 statements to perform a single logical operation, there is still value in summarizing each block with a comment, even if the function isn't "too long".

[gnaritas]

That's what function names are for. Comments don't need to summarize. A useful comments says why code is this way, it doesn't summarize or repeat code.

[flatline3]

> That's what function names are for.

A single function for every 3-4 line operation would result in incredibly disjointed code, and would require more explicit documentation of invariants because that function can now be called elsewhere (at least inside of the given translation unit).

> A useful comments says why code is this way, it doesn't summarize or repeat code.

That's nonsensical. Why wouldn't you want to abstract the complex?

[gnaritas]

I abstract code with code, not with comments. Comments in general stink, and are used to express what code can't. If I can express it in code, it doesn't need a comment. Every comment is a sign that you failed to write expressive code.

If you need a comment to say what the next four lines do, you need a function for that, not a comment.

[arethuza]

You would actually write an "Increment the total" comment?

[spiffytech]

Some people certainly do! My favorite examples of how not to write comments are these code snippets from the API guide I was given at a previous job. The other 60 pages of API documentation are just like this- all what and no why.

The problem isn't that these comments are harmful (they're not), but that inserting these comments made the coder feel like they'd done their job of commenting their code well, when in actuality the comments provide no insight to why certain things are called or instantiated, or what certain values represent; critical knowledge one needs to extend the code beyond the specific example cases the API guide presented.

----

  ‘ A for loop iterates through each row of DataGridView
  For Each row In DirectCast(Me.DataGridView1.Rows, IEnumerable)

----

  Dim frmTakeBackTask As New TakeBackTask
  ‘ Public oTaskData of TaskBackTask gets populated from the local object oTaskData
  frmTakeBackTask.oTaskData = oTaskData

----

  ‘ A For loop is initiated to iterate through each child node contained 
  ‘ in the XML document
  For Each record In xmlDoc.ChildNodes.ItemOf(0).ChildNodes
      ‘ A nested For loop is initiated to iterate through each column
      For Each column In record.ChildNodes

[jbl]

I probably wouldn't write "increment the total", but I think it makes sense to comment on what the total is/represents, or why the total is incremented in some particular way (if it's non-obvious).

My beef with "increment the total" comments is not that they are there, but rather that they don't help me get the big picture.

[flatline3]

That example is rather hyperbolic and not particularly useful. I can't recall the last time in 15 years that I thought "this code has too many comments!"

[gms7777]

Back in college I was a teaching assistant for CS classes and graded a lot of what was very often very poorly written and majorly undercommented code. But I do remember once getting an incredibly unnecessary 2 page long comment for a 10 line function.

That may be the only time that thought has gone through my head.

At my first internship, the code base had basically no comments in it, but was in general very clean, very organized, and there was a ton of thought put into naming and organization for readability. It was a good exercise for me working like that because it forced me to not rely on comments to explain messy code. But I also remember having long debates about what to name a variable to make it perfectly clear to the next person reading this code what it does (and often times ending up with excessively long variable names) and thinking "wow...this is a waste of time. You could just add a 1 line comment"

[dahvyd]

Consider the standard Java cough paradigm used by multitudes of developers, and on by default in many Java IDEs:

    /* Gets the person's name
       @returns the person's name */
    public String getName() {
       return name;
    }

That is insane. The comment adds nothing to anyone's day and helps no one better understand the method than after simply reading the method signature.

[flatline3]

It generates auto-docs, which are useful. It's just a ridiculously verbose way to do it, and it would be preferable if the documentation could be generated without the repetitive comment.

[arethuza]

"I can't recall the last time in 15 years that I thought "this code has too many comments!""

I've thought that every time I see a source file that contains an automatically generated header built from the revision history.