Using tabs effectively. Was: Why not use tabs?

[James Logajan]

Robert Meegan wrote:
> Absolutely nothing is wrong with tabs, as long as you only use tabs.
> The problem comes when people mix tabs and spaces, because it would
> seem that every programmer on Earth uses a different default tab width
> (I'm lucky, I got in when three spaces per tab was still available).
> 
> Some people use eight-space tabs and type four spaces for an
> indentation level so that their code has indentation:
> 
> <-->
> <- \t ->
> <- \t -><-->
> <- \t -><- \t ->
> 
> etc.
> 
> When you import this into your editor (set to three-space tabs, like
> God intended) the effect is horrific.

Under Solaris and Linux (and probably most other Unices) there exist the
commands:

expand
unexpand

Read their man pages. Note that they take an option about how wide tabs are
to be interpreted. Also note that some versions (BSD?) of the "pr" command
also have the "-e" option for setting tab width.

The issue of "how many spaces to a tab" is an old enough problem *in all
languages* that I'm surprised that it has never become a convention to put a
comment at the top of all source files indicating what the tab settings for
decent viewing should be. I've come across a lot of source code where tabs
were intended to be every 4 characters to conclude this is a sizable number
of authors. (I used to use 3 spaces/tab early in my career.) The fact that
some languages like Python are sensitive to the issue detracts from them not
a wit in my opinion.

I humbly offer the following rules to a long and healthy editing experience:

1.0) If using tabs (regardless of tab setting):
   1.1) Use nothing but tabs for indentation!
        Do not mix tab and space indentation!
   1.2) Indent at whole multiples of your tab settings lest you make it
        impossible to conform to rule 1.1.
   1.3) Place a comment at the top of your file indicating the tab
        spacing. Even if using tab settings at 8.
   1.4) Run the unexpand utility (if on Unix) on the file to minimize
        the chance of accidentally violating rule 1.1.
2.0) If using spaces:
   2.1) Use nothing but spaces for indentation!
        Do not mix space and tab indentation!
   2.2) Place a comment at the top of your file indicating that tabs
        do not exist as indentation and should not exist.
   2.3) Run the expand utility (if on Unix) on the file to insure
        that you have not accidentally violated rule 2.1 and 2.2.
3.0) If trying to impose a particular tab setting as standard:
   3.1) Try using a thimble to turn back the tide, as you will have better
        luck at success at that than in imposing a specific tab spacing
        as "correct".

Rules to follow for extra credit:
4.0) For lines longer than 80 characters:
   4.1) Keep all lines under 80 characters and manually insert line
        breaks at reasonable points. Do not rely on automatic editor
        line wraps.
   4.2) If reasonably possible, (and it normally is) indent line
        continuations to at least the same indentation level as the
        continued line. (Much like the sentences in these paragraphs
        have been "continued" at the same indentation level.)

5.) Don't expect any of these rules to be followed except this one.


P.S. I sure hope Netscape Communicator didn't convert any of my spaces to
tabs! ;)