[Haskell-beginners] Combining IO and Either function to "EitherT e IO a"

[David Thomas]

Agreed on all counts.


On Wed, Mar 5, 2014 at 3:35 PM, Brent Yorgey <byorgey at seas.upenn.edu> wrote:

> On Wed, Mar 05, 2014 at 03:22:39PM -0800, David Thomas wrote:
> > It's a function of zero arguments.
>
> This is really stretching the meaning of the word "function" beyond
> any reasonable, useful definition, in my opinion.  See the discussion
> here:
>
>   http://conal.net/blog/posts/everything-is-a-function-in-haskell
>
> A much more useful (and precise) point of view is that in Haskell, all
> functions take exactly one argument.  Under that view, of course,
> there is no such thing as a function of zero arguments.
>
> > It's also sort of, kind of a function
> > from RealWorld to (String, RealWorld) if you squint.
>
> I'm don't think this is a very helpful way to understand IO, though it
> is probably closer to the sense in which the OP understood IO String
> to be a function.
>
> My guess is that what is really going on here is a confusion of
> terminology from imperative languages, some of which use the word
> "function" for everything, whether they take any arguments or not,
> return any values or not, have any side effects or not, etc.
>
> -Brent
>
> > On Wed, Mar 5, 2014 at 10:18 AM, Kim-Ee Yeoh <ky3 at atamo.com> wrote:
> >
> > >
> > > On Thu, Mar 6, 2014 at 12:49 AM, Nathan Hüsken <
> nathan.huesken at posteo.de>wrote:
> > >
> > >> Mmh, I might not have used haskell terminology correctly. Its a
> function,
> > >> in the sense of a function of an imperative language ...
> > >
> > >
> > > Yes, you could model IO String in C as a function taking void and
> > > returning a pointer to char.
> > >
> > > Calling an IO String a Haskell function would confuse a lot of people.
> > >
> > > -- Kim-Ee
> > >
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