[Haskell-beginners] question about list processing

[Dennis Raddle]

Speaking of lists and history, I noticed that a lot of library functions
which were formerly defined over lists (when I first looked at Haskell six
years ago) are now defined on Traversable, which makes it a lot harder for
beginners to read the documentation. I have been playing with Haskell for
five years, but not much, so I'm still a beginner. I just mentally
substitute lists when I see Traversable.

I only really use lists and Maybe, as far as instances of the typeclasses
go. That's only two types, but a lot to learn!

D




On Thu, Nov 12, 2015 at 5:42 AM, akash g <akaberto at gmail.com> wrote:

>
> http://stackoverflow.com/questions/7463500/why-do-we-have-map-fmap-and-liftm
> have very good answers on this.
>
> On Thu, Nov 12, 2015 at 7:11 PM, akash g <akaberto at gmail.com> wrote:
>
>> map is specialized for lists while fmap is for any functors.  Its
>> presence is historical.  Prefer fmap over map.
>>
>> On Thu, Nov 12, 2015 at 7:03 PM, Dennis Raddle <dennis.raddle at gmail.com>
>> wrote:
>>
>>> Just after I posted that question, I started driving home, and on the
>>> drive I thought of your answer. I think I'm starting to ask the right
>>> questions when I'm programming in Haskell. Like redundancy and bloat is a
>>> sure sign that a more witty expression is available, and that I should
>>> consult the typeclasses.
>>>
>>> Second, I am not used to the implications of laziness, so it took me a
>>> while to hit on your solution because I keep thinking you have to map
>>> something over the whole list, and that if you only want to map it over the
>>> head, you are stuck.
>>>
>>> You can use 'map' also, instead of 'fmap', right? Is 'map' just 'fmap'
>>> for lists?
>>>
>>> D
>>>
>>>
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>>>
>>
>
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