[Haskell-beginners] Functors and Applicatives; I'm just not getting it ...

[Erik Price]

As the name implies, the concept of an applicative functor builds on the
concept of a functor, so it will help to start with a thorough
understanding of functors.

A functor allows you to lift a function of Foo -> Bar into some context of
Foo, so that when the expression is finally evaluated you will end up with
a value of Bar in that context. An applicative functor allows you to lift a
function of an arbitrary number of parameters, such as Foo -> Bar ->
Baz, into that number of values (of those types) already in contexts. So
the example function could be applied to a context of Foo and a context of
Bar, and would ultimately evaluate to a context of Baz.

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On Sunday, October 19, 2014, Frank <frankdmartinez at gmail.com> wrote:

> Thanks but I think this misses the point a bit. A some point in time, I
> will need an explanation about applicatives and teg supposedly best
> documentation (or at least the documentation I see advocated in numerous
> places) seems really bad at providing that explanation, a point I find
> worrisome. I know myself well enough to say becoming comfortable with
> functors will not make understanding applicatives any easier if the
> applicatives explanation is not clear and, right now, the explanation is
> not clear.
>
> On Sunday, October 19, 2014, Karl Voelker <karl at karlv.net
> <javascript:_e(%7B%7D,'cvml','karl at karlv.net');>> wrote:
>
>> I suggest that you ignore applicatives for now and just focus on
>> plain-old functors. They are the simplest part, and once you are confident
>> in dealing with them, adding on applicatives will be much easier.
>>
>> And, although it can be difficult when you are really lost, if you can
>> ask some more specific questions, this list will provide plenty of answers.
>>
>> -Karl
>>
>> > On Oct 18, 2014, at 3:37 PM, Frank <frankdmartinez at gmail.com> wrote:
>> >
>> > I've had a go at LYAH and CIS 194 and the Typeclassopedia and I just
>> don't get get functors and applicatives. I'm simply not understanding them,
>> what the various symbols/keywords mean, what they represent, how to think
>> of them, etc. Nothing. Is there any kind of documented model I should be
>> considering? Is there a "functors and applicatives for Dummies" I should
>> read? Should I just give it up, not bother with Haskell and just stick to
>> scheme/ruby/C++?
>> >
>> > --
>> > P.S.: I prefer to be reached on BitMessage at
>> BM-2D8txNiU7b84d2tgqvJQdgBog6A69oDAx6
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>
> --
> P.S.: I prefer to be reached on BitMessage at
> BM-2D8txNiU7b84d2tgqvJQdgBog6A69oDAx6
>
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