[Haskell-beginners] How best to do this?

[emacstheviking]

What about a new compiler flag to highlight all such potential gotchas?

  --n00b

;)
Would help me out no end...

On 1 May 2013 11:35, Michael Peternell <michael.peternell at gmx.at> wrote:

> @Brent:
> By reading your mails I got an idea...
>
> how about generating a compiler warning when someone types a literal like
> [5..2].
>
> "Foo.hs:32: Warning: Literal list [5..2] evaluates to [] because 5 > 2 and
> the default step size is +1. Replace the literal with the empty list or
> with [5,4..2] to suppress this warning."
>
> That would be a really beginner-friendly warning.
>
> But I also think that we shouldn't catch this kind of mistake at runtime,
> because it may be the expected behavior in many cases.
>
> Michael
>
> Am 29.04.2013 um 23:54 schrieb Brent Yorgey:
>
> > Oh, yes, I suppose it could.
> >
> > In any case, I am still in favor of the existing semantics -- it is
> > simple and consistent (and sometimes even useful).  "Do what I
> > mean"-style semantics with special cases end up generating more pain
> > than they solve.
> >
> > -Brent
> >
> > On Mon, Apr 29, 2013 at 02:29:43PM -0400, David McBride wrote:
> >> Couldn't it just use fromEnum and compare the integers you get and
> >> figure out which is bigger?
> >>
> >> On Mon, Apr 29, 2013 at 2:17 PM, Brent Yorgey <byorgey at seas.upenn.edu>
> wrote:
> >>> But then \x y -> [x .. y]  would have to have the type
> >>>
> >>>  (Ord a, Enum a) => [a]
> >>>
> >>> whereas now it just has the Enum constraint.  Either that or else the
> >>> notation would work differently for literals vs. expressions but that
> >>> would be just awful.
> >>>
> >>> -Brent
>
>
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