Re: [Caml-list] O'Caml looks at the contents of comments?!

[skaller <skaller@ozemail.com.au>]

On Sat, 2003-09-13 at 20:45, Jim Farrand wrote:
> I've spent a long time puzzling over a "string not terminated" error
> which was being reported inside a class I'm writing.  Camlp4r reported
> the error just as being somewhere in the class (i.e. Line 267 character
> 4 - 1076) which gave me quite a bit of code to look over.  I spent a
> long while staring at the code quite puzzled because I couldn't see an
> unterminated string anywhere.
> 
> Eventually I started commenting out bits of code, and I was even more
> confused when I'd commented out the entire class and STILL got the
> error.
> 
> Eventually I traced the error to an unterminated string inside a
> comment.  This strikes me as slightly odd behaviour - one of the first
> things comp sci students are taught about comments is that the compiler
> ignores them.  As this has been my experience for many years it took me
> a long time to even consider that I could have a syntax error inside a
> comment.
> 
> So why is this restriction enforced?
> 

The reason is: Ocaml comments are designed to be able to
comment out code.

If you consider the code:

	" (* " ^ x

and comment out the first part like this:

	(* " (* " ^ *) x

it wouldn't work unless the (* in the string was detected
as being inside a string and ignored. The contents of
comments are not ignored, in the sense that every lexer
even C's, has to find the comment terminator.

Bash and C++ comments:

	# ....
	// ....

do not have this problem, since they're terminated
by end of line.

Also: Ocaml, wrongly I think, allows strings to
span lines. 

Hmm .. Felix doesn't do the string detection .. which
means its nestable /* .. */ comments wont
wrap code containing strings containing /* or */ .. 
Hmmmm .. thanks for raising this issue  ..



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