[erlang-questions] Multi-line comments in Erlang

Richard O'Keefe <>
Thu Dec 9 21:58:21 CET 2010


On 9/12/2010, at 10:48 PM, Zvi . wrote:

> 1. The beauty of dynamic languages is that you don't need tools and IDEs!

What has this to do with >dynamic< languages?
The only language I use an IDE for is Smalltalk (which is dynamic).

Erlang/OTP comes with lots of tools.

As for editors, excluding help files, the editor I use is
13100 lines, 6770 SLOC, 381 kiB in size and originally ran
on PDP-11s and used to run on MS-DOS.

> 2. Comments are essentially Natural language (let's say US English)
> document, embedded into Programming language (Erlang) document.

People who ask for multiline and nesting comments often want them to
contain program text.

> Therefore, embedded document should be left intact.

This is not a valid conclusion.  People who use Javadoc, Haddock (for
Haskell), PlDoc (for Prolog), or ErlDoc (for Erlang) *want* their
natural language text to be marked up in various ways and transformed
for display.  There has long been a fashion in C for writing
	/* long comments
         * with stars at the
 	 * beginning of every line
	 * and a lopside end
	 */
which I have always found ugly.  But the existence of that fashion
shows that there are many people who find value in their commentary
being explicitly marked.

> Ideally I would like comments to be something, like HEREDOC.

Other people want a clear and unambiguous separation between
what is commentary and what is not, so that you can look at
_any_ line in a file and instantly tell what you are looking at.
> 
> 3. Free format is the king!

A non-sequitur.  Ada is free format, but it has only -- end of line
comments.  Fortran 95 is free format, but it has only ! end of line
comments.  

> Language designers shouldn't dictate programmers
> how to format and ident their code.

Somebody forgot to tell Larry Wall and Guido van Rossum that;
they also forgot to tell the Haskell designers and the Occam designers.

> How differnt is starting comment line from '%' in Erlang, from putting 'C'
> or '*' in the first column in FORTRAN?

Very different.  % in Erlang is like ! in Fortran: you can put it in
any column you choose.
> 
> 4. In other languages, that doesn't have multiline comments I often use
> ifdef(false) macro, or outright if(false) to "comment out" parts of code.

This contradicts your earlier statement that the contents of multiline
comments are natural language text.

> I
> think it's uglier, than proper multiline comments, but still better than
> comment every single line.

Erlang also has -if.




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