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While vs for

Stefanos Kouroupis on July 19, 2019

This is a fun little story. A few months ago I wrote the following function, due to a need to get the index of a specific occurrence of a character...

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Danny McGee • Jul 19 '19 • Edited

I don't necessarily think that for loops are inherently easier to read than while loops, but I think if you're doing a typical incrementing/decrementing-iterator-variable loop it probably makes more sense to use for since that's the reason for exists.

I'll typically only use while if I need to check some other sort of condition that doesn't fall neatly into that pattern. As an example, I'm currently building a syntax highlighter for the web (mostly for fun), and I have a method like this:

parseLine(this.current.line) {
  while (this.current.line.length > 0) {
    this.tokenize(this.current.line);
  }
}

tokenize tries to match the beginning of the line (which is a string) for a number of different regex patterns, assigns the match a token, and then removes the match from the front of the line. So each time it's done, the line will be a little shorter, but it's impossible to know by how much ahead of time, which makes the while loop the correct tool for the job in this particular case. That's my thinking anyway.

Gabi • Jul 19 '19

Hi, in this case i find the for loop way more developer friendlier and easier to understand. Thanks for sharing this.

Stefanos Kouroupis • Jul 19 '19

I am trying to understand as to why is a for loop friendlier than a while loop

because to I've heard a similar thing for switches in the past compared to ifs

Fabian Holzer • Jul 19 '19

I don't think the code comprehension problems have anything to do with the type of loop, but with the density of the code. If I look at the while loop you wrote, I do not only see a condition, but also up to two side effects (depending on whether or not the evaluation is short-circuited). This single line has up to four different responsibilities.

I actually think a while loop is the more suitable option, but maybe the introduction of one or two explanatory variables could enhance readability a lot.

Stefanos Kouroupis • Jul 19 '19

Code comprehension though is not always a objective term. Sometimes it heavily depends on a person's perception. Throughout my career I've seen different styles of coding and I tend to accept them.

In this case they felt that for is more readable so I let them change it (for me it's tom[a]to, tomat[o]). Now if they chose, to do it with recursion, again I wouldn't object to it.

Recursion is another fine example of a style. Some people love it, it make sense to them. Others are afraid of it.

once we had a guy that only wrote decrementing-for-loop...nowadays everyone hates his legacy code. But if you ask me...they get stuck at details and not the big picture, and the big picture is that he code was a freaking masterpiece. Sometimes hard to read, but he wrote the most resilient consumer services I've ever seen.