C/C++ Best indentation length?

Question

I was reading a Vim tutorial ( http://www.oualline.com/vim-cook.html#drawing ), and came across this:

This is very useful if you use a 4 space indentation for your C or C++ programs. (Studies at Rice University have shown this to be the best indentation size.)

Is there any truth in these studies?

Note-- i didn't mean for a flame war in indentation -- just whether anyone else has come across tis study before? EDIT: @MaR I made a poll http://poll.fm/3d5kg

Answer 1

There is no single best tab size, period.

Larger tab sizes means better visual separation, but you'll be using more horizontal screen space. Conversely, smaller tabs reduce visual separation, but allow for more code per line, and produce smaller 'jumps' that could otherwise disturb the reading flow.

Personally, I find that 3 or 4 spaces is the minimum size that produces sufficient visual separation; 4 is a safe bet, 3 works for some fonts, but not all. Others might disagree; some people use 2 spaces and are perfectly happy with it.

If the tab size is too high, visual separation doesn't improve, but the longer jump reduces readability. 8 spaces is probably the maximum that can be read comfortably, and I have never seen anyone use more than that.

So anything between 2 and 8 is fair game. If you work on code that needs deep nesting (say, C++ - a simple inline method with two levels of nested loops in a namespace uses five to six levels of indentation already), you'll want to lean toward smaller indentation; if you have a large monitor and can afford long lines, you may want to go large; etc. Generally speaking, 4 and 8 seems to be the most common choices (probably because programmers like powers of 2), with 4 being more popular than 8. (On a side note, the official Python style according to PEP-8 prescribes 4 spaces).

Just find something that works and use it.

Answer 2

Without finding a paper published from these studies at Rice we can't really comment on the claim (shame the vim cookbook doesn't reference it). After several searches I can find a few more casual remarks about this study, but no proper citations and no paper.

For modern C++ I'd certainly use indent of 2 as the long lines now common from template parameters benefit from the extra horizontal space, it's possible the Rice study wouldn't have taken this into account (but without seeing a paper we will never know). xml I also indent by 2 for similar reasons.

For other languages I tend to use the editors default, which mostly is 4 (which lends some anecdotal evidence to 4 being good)

Answer 3

Programming style is like "taste": very subjective.

Studies are based on "statistics". They keep a number of programmer and ask how do they code, then keep another number of programmers and ask them how do they feel reading some code.

Although it can be true that the majority of them feel more comfortable with 4 spaces it doesn't mean that you have to be comfortable with it.

Find yourself your comfortable style: something that look "pretty" to your eyes, and makes you able to focalize the "important things", like where something begins and ends, and is "resilient" to mistakes (intending that makes coding mistakes to look "odd", hence easy to be found) and be coherent with it.

There are lot of editors that allows code reformatting with various styles and parameters. If I have to rework your code and I find it hard to read, it's not a problem form me to reformat in another way, more suitable to my eyes.

Answer 4

Together with indentation, comes the complexity of the program.

From my own experience, whenever I find myself indenting too far, I know that it is time to break things in smaller parts, possibly by changing the design.

About indentation itself, usually I work on projects where it is specified in coding rules document. I have worked with 2, 3 and 4 spaces and I have no rational argument in favour one any of these values.

Anyway, I never indent with tabs because in a team of, say, 3 developers, at least three editors are used and at most one developer knows how to configure its editor for tabs and indentations. The result is a code that is correctly indented on one workspace and is unreadable on the others.

Answer 5

I find 4 spaces indentation the most comfortable.

But it really depends on the person - your preferences, what you're used to, and also on the size of the letters on the screen and the size of the monitor.

I wouldn't claim that there's a single value that is perfect for everyone, but 4-spaces seems to be a rather convenient compromise.

Keep in mind that you're writing a code that other people would be reading. People like me for example, the four-eyes:-)

And as I commented on the other question: I find it much more comfortable for me and others to have the style defined, at least on some basic level, as part of the coding standards, and enforced (even by automatic beatufy on check-in).

Answer 6

Space size is going to be pretty simple. More spaces makes the program harder to read by virtue of consuming more space on the screen. They also make the program easier to read by making the indentation differences more exaggerated. Therefore, the optimum space size is going to be the minimum space that most, if not all, programmers can clearly distinguish in a small amount of time. That sounds fairly measurable to me.

I've never actually see any study on this, though.