[Haskell-beginners] Re: map question

[Daniel Fischer]

Am Sonntag 18 Oktober 2009 22:57:38 schrieb Will Ness:
> Daniel Fischer <daniel.is.fischer <at> web.de> writes:
> > Am Sonntag 18 Oktober 2009 13:11:07 schrieb Will Ness:
> > > (2`mod`) is a unary operation :: (Integral a) => a -> a. Putting it
> > > inside backticks would require it be a binary infix op, causing a type
> > > mis-match.
> >
> > instance (Integral a) => Integral (b -> a) where ...
> >
> > Evil, yes, but then f `(2 `mod`)` x would type-check.
>
> Any problem that could be introduced for operators could be introduced for
> the regular named values as well.

But allowing only one level of backticks, and only on plain identifiers limits the scope 
of possible problems.

>
> > But anyway, there are operators where a backticked section would
> > type-check:
> >
> > f `(g `.`)` x
> >
> > That's not good.
>
> Why? Is it not just (g .) f x ? What's the problem with it?

It's incredibly ugly, looks almost like a perl regex.