[richardwhiuk]

Comments are often a code smell. In lots of examples, better variable naming, breaking something out into a function, or constants often reduces the need for a code comment.

[kickopotomus]

I disagree. Code ages and people move on. 2 years down the line some new guys are maintaining the code base. Some new guy is testing the system and notices that sales tax values seem to be "strange" for Kerplakistan on certain days of the week so they create a ticket for it. Then that goes through the typical pipeline. Another member of the team gets assigned the issue and looks into it. They come across the line:

  return nil if country_code==KERPLAKISTAN and day_of_week==MONDAY

Hmm.. Well that's strange. I don't have a background in Kerplakistan monetary policy so I don't know why we aren't assessing sales tax on Monday. Perhaps Kerplakistan is a special case. Is that being handled somewhere downstream? Then 1-2 hours later, after shuffling through source and eventually just Googling Kerplakistan sales taxes, you discover what someone found out 2 years ago when they wrote that line. Now you resolve the ticket and move on with your day but you just wasted a couple man-hours on a non-issue that could have been resolved instantly from a code comment.

Comments are as much for the next guy as they are for you.

[richardwhiuk]

Without a more concrete example, it's difficult to suggest what the better fix would be.

Code smell doesn't mean you should never do it, just that often there's a better way.

[JohnBooty]

Here's a more real-world example.

I worked on an enterprisey line of business app that assigned sales leads to salespeople.

The algorithm to do this was a multi-step process that was (1) rather complex (2) constantly being tweaked (3) very successful (4) contained a number of weighting factors that were utterly arbitrary even to veterans of this app.

It was full of many `if country_code==KERPLAKISTAN && day_of_week==MONDAY` -style weighting factors. Each represented some hard-won experience And when I say "hard-won" I mean "expensive" -- generating leads is expensive business.

We had a strong culture of informative commit messages, but this file had hundreds if not thousands of commits over the years.

It was the kind of code that resisted serious refactoring or a more streamlined design because it was a recipient of frequent change requests.

A few human-readable comments here and there went a loooong way toward taming the insanity and allowing that module to be worked on by developers besides the original author.

Knowing the why for many of these rules made it much easier to work with, and also allowed developers to be educated about the business itself.