Fergus Henderson <[EMAIL PROTECTED]> writes:
> On the Standard Haskell site,
> Alastair Reid wrote:
> >
> > 1) Fixity declarations usually look like this:
> >
> > infixl 6 +, -
> >
> > but you can omit the precedence digit and write this instead:
> >
> > infixl +, -
> >
> > The programmer who uses this avoids having to type 2 characters.
> > The programmers who'sre reading this code has to learn that
> > the precedence digit can be omitted (I didn't believe it when I
> > first saw it) and then look up the default precedence in the report.
> > I think it is harder to understand programs that use this shortcut
> > and that it should be removed.
>
> I don't think it's harder. Even if the number is specified explicitly,
> I would *still* have to look up the precedence table in the report,
> or at least grep the source for the standard prelude, because
> I don't know what the precedence of the other operators is.
I think you're missing the point. Omitting the precedence digit is
important because it allows the programmer to avoid making a decision
about something he doesn't really care about. Most of the time,
you're not interested in the relative precedence of `thenP` vs. (+),
since it doesn't make any sense to mix them.
If you really *want* a precedence of 9 (or whatever the default is),
one would never dream of leaving it out of the declaration.
ObStandardHaskellProposal: relax the restriction on precedences being
in the range 0-9. Change the precedences of the Prelude operators
from n to n*100.
Cheers,
Simon
--
Simon Marlow [EMAIL PROTECTED]
University of Glasgow http://www.dcs.gla.ac.uk/~simonm/
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