Tabs versus Spaces in Source Code

[Mumia W.]

Xah Lee wrote:
> Tabs versus Spaces in Source Code
> 
> Xah Lee, 2006-05-13
> 
> In coding a computer program, there's often the choices of tabs or
> spaces for code indentation. There is a large amount of confusion about
> which is better. It has become what's known as “religious war” —
> a heated fight over trivia. In this essay, i like to explain what is
> the situation behind it, and which is proper.
> 

Thanks Xah. I value your posts. Keep posting. And since your posts 
usually cover broad areas of CS, keep crossposting. Don't go anywhere 
Xah :-)


> Simply put, tabs is proper, and spaces are improper. Why? This may seem
> ridiculously simple given the de facto ball of confusion: the semantics
> of tabs is what indenting is about, while, using spaces to align code
> is a hack.
> 

I wouldn't say that spaces are a hack, but tabs are superior.

> Now, tech geekers may object this simple conclusion because they itch
> to drivel about different editors and so on. The alleged problem
> created by tabs as seen by the industry coders are caused by two
> things: (1) tech geeker's sloppiness and lack of critical thinking
> which lead them to not understanding the semantic purposes of tab and
> space characters. (2) Due to the first reason, they have created and
> propagated a massive none-understanding and mis-use, to the degree that
> many tools (e.g. vi) does not deal with tabs well and using spaces to
> align code has become widely practiced, so that in the end spaces seem
> to be actually better by popularity and seeming simplicity.
> 

Don't forget the laziness of programmers like me who don't put the 
tabbing information in the source file. Vim deals with tabs well IMO, 
but I almost never used to put the right auto-commands in the file to 
get it set up right for other users.

> In short, this is a phenomenon of misunderstanding begetting a snowball
> of misunderstanding, such that it created a cultural milieu to embrace
> this malpractice and kick what is true or proper. Situations like this
> happens a lot in unix. For one non-unix example, is the file name's
> suffix known as “extension”, where the code of file's type became
> part of the file name. (e.g. “.txt”, “.html”, “.jpg”).
> Another well-known example is HTML practices in the industry, where
> badly designed tags from corporation's competitive greed, and stupid
> coding and misunderstanding by coders and their tools are so
> wide-spread such that they force the correct way to the side by the
> eventual standardization caused by sheer quantity of inproper but set
> practice.
> 
> Now, tech geekers may still object, that using tabs requires the
> editors to set their positions, and plain files don't carry that
> information. This is a good question, and the solution is to advance
> the sciences such that your source code in some way embed such
> information. 

Vim does this. We just have to use it.

 > This would be progress. However, this is never thought of
> because the “unix philosophies” already conditioned people to hack
> and be shallow. In this case, many will simply use the character
> intended to separate words for the purpose of indentation or alignment,
> and spread the practice with militant drivels.
> 
> Now, given the already messed up situation of the tabs vs spaces by the
> unixers and unix brain-washing of the coders in the industry... Which
> should we use today? I do not have a good proposition, other than just
> use whichever that works for you but put more critical thinking into
> things to prevent mishaps like this.
> 
> Tabs vs Spaces can be thought of as parameters vs hard-coded values, or
> HTML vs ascii format, or XML/CSS vs HTML 4, or structural vs visual, or
> semantic vs format. In these, it is always easy to convert from the
> former to the latter, but near impossible from the latter to the
> former. And, that is because the former encodes information that is
> lost in the latter. 

Nope. Conversion is relatively easy. I've written programs to do this 
myself, and everyone and his brother has also done this. Virtually every 
programmer's editor that I've ever used can do this, and a great, great 
many independent programs convert tabs to spaces. It's like saying, 
"it's near impossible to write a calculator program." :-)

I bet that someone has a Perl one-liner to do it.

On any Debian system, try a "man expand" and see what you find. Also, 
emacs and vim do it. Perl has a Text::Tabs module. TCL's 
::textutil::(un)?tabify routines do it. The birds do it, and the bees do 
it. Oh wait, that's something else :-)

 > If we look at the issue of tabs vs spaces, indeed,
> it is easy to convert tabs to spaces in a source code, but more
> difficult to convert from spaces to tabs. 

Nope again. It's easy, you just keep track of the virtual character 
position as you decide whether to write a space or a tab. Computers do 
the "counting" thing fairly well.

 > Because, tabs as indentation
> actually contains the semantic information about indentation. With
> spaces, this critical information is lost in space.
> 
> This issue is intimately related to another issue in source code:
> soft-wrapped lines versus physical, hard-wrapped lines by EOL (end of
> line character). This issue has far more consequences than tabs vs
> spaces, and the unixer's unthinking has made far-reaching damages in
> the computing industry. Due to unix's EOL ways of thinking, it has
> created languages based on EOL (just about ALL languages except the
> Lisp family and Mathematica) and tools based on EOL (cvs, diff, grep,
> and basically every tool in unix), thoughts based on EOL (software
> value estimation by counting EOL, hard-coded email quoting system by
> “>” prefix, and silent line-truncations in many unix tools), such
> that any progress or development towards a “algorithmic code unit”
> concept or language syntaxes are suppressed. I have not written a full
> account on this issue, but i've touched it in this essay: “The Harm
> of hard-wrapping Lines”, at
> http://xahlee.org/UnixResource_dir/writ/hard-wrap.html
> ----
> This post is archived at:
> http://xahlee.org/UnixResource_dir/writ/tabs_vs_spaces.html
> 
>    Xah
>    xah at xahlee.org
>  ∑ http://xahlee.org/
> 

I've never thought of tabs-vs-spaces as a religious war. Anyway, the 
authority of the programming environment will determine which one is 
used. Have a good week Xah.