Re: On Tabs and Spaces

From: Christer Weinigel <christer@weinigel.se>
Date: Oct 16, 2007, 23:51 UTC
Message-ID: <20071017015109.303760cc@localhost.localdomain>
In-Reply-To: <alpine.LFD.0.999.0710161559150.6887@woody.linux-foundation.org>

On Tue, 16 Oct 2007 16:05:34 -0700 (PDT) Linus Torvalds <torvalds@linux-foundation.org> wrote:

Show 14 quoted lines

> I do indeed. I don't think it's sensible. And I did think I already 
> answered that issue by talking about how most editors don't even
> support it or show the difference between tabs and spaces.
> 
> For example, the editor I use - microemacs - supports tabs just fine.
> It does auto-indentation etc. But it does it with hard-tabs by
> default, so now you have to have some editor-specific setup for that
> particular project if you ever want to do anything else.
> 
> And that's really what it boils down to. Everybody support
> 8-character hardtabs (and usually by default). They may support other
> things *too*, but any time you move away from that standard
> behaviour, you'll most likely find something that doesn't support the
> alternatives.

Unfortunately most editors are totally confused about the difference between tab size and indentation level. Visual Studio, probably the most commonly used development environment on Windows, by default uses TAB characters that are 4 spaces wide, and users are recommended not to change that because of that a lot of existing Windows source code and examples uses those settings.

Two years ago, when I last looked at it, Eclipse, a very commonly used development environment, managed to confuse tabs and indentation and make it almost impossible to write Java or C code with a tab size of 8 with a different indentation level. The Eclipse 3 betas did see some improvement there, I think it got possible to do the right thing in Java at least, but the normal text editor and C editor lagged behind. But it was still a big mess and it was much too easy for someone to get a tab size which is not 8. Hopefully this has been fixed by now, but I wouldn't bet any significant amount of money on it.

Nedit (which runs on Linux) has a very confusing settings dialog with terms such as "tab spacing", "emulated tabs". I guess emulated tabs means the indentation level, but guess how easy that is to mess up.

gedit can control the tab width, but has no setting at all for configuring the indentation level. Guess what people do when they want a 4 space indentation level? Yes, right, change the tab size to 4.

A a former colleague who used visual slickedit usually produced code with tab size 4. I think I've gotten the same crap from ultra edit 32 users.

And so on... Mercifully, _all_ of these editors have a setting to use spaces instead of tabs, and telling people to turn on that setting is the absolutely easiest way of making things "just work". Yes, I know, the correct answer is to tell people to always use tab size 8, and I frequently and loudly do that. But at the same time, perfect is the enemy of good. It's much easier to explain "tabs will act differently in different editors, but if you always us spaces it will not be a problem" than to get into a discussion about the semantic difference between tab size and indentation.

If you assume that everyone is sane and use a tab size of 8 you will get bitten, sooner or later. Or actually, you, Linus, who are lucky enough to work mostly with Linux source, you might personally not get bitten all that often. But us poor suckers that have to work with other people, often Windows programmers, we do.

  /Christer