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

[Tim Perry]

Thanks Brent. Your posts and the link helped.


On Wed, Mar 5, 2014 at 3:38 PM, David Thomas <davidleothomas at gmail.com>wrote:

> 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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