Comment Syntax

Josef Svenningsson josef.svenningsson at
Thu Feb 2 05:17:39 EST 2006

On 2/2/06, Henrik Nilsson <nhn at> wrote:
> Hi all,
> To corroborate Wadler's law further.


Josef wrote:
> > Oh yes, it does happen that a single line comment begins with a
> > special symbol. It has happened to me on several occations when using
> > haddock annotation to my source code. It is all to easy to forget that
> > extra space. With incomprehensible error messages as a result.
> But might that not just mean that the error messages ought to be
> improved?
> I don't know how hard that would be, but after having played around
> a bit with GHC, the messages I get are either of the type
> "parse error on input '--|'" or of the type "Not in scope: `-->'"
> (followed by lots of other stuff not being in scope etc).
> If this really is a big problem for beginners, it would not seem
> totally infeasible to add some special code that helpfully suggests
> that a space perhaps ought to be inserted?
> Or have you seen significantly worse error messages?

My point here was not that the error messages was that terrible.  I just
wanted to point out to Manuel that it does happen that single line comments
start with a symbol. Which makes the current comment syntax somewhat


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