The (`elem` members) function will tell you if the person is a member of members. You can then turn that boolean into your custom State type.

On Dec 3, 2015 11:46 PM, "Jeon-Young Kang" <jykang22@gmail.com> wrote:

Hi all.

I'd like to apply lookup function (Data.Map) for what I am working on.

Here is my code.

data Person = Person {personId :: Int, name = String}

data People = [Person]

data State = InMembership | NoMemebership

person1 = Person {1 = personId, "James" = name}

person2 = Person {2 = personId, "Tom" = name}

members = People [person1, person2]

class Belonging a where

      belonging :: a -> [a] -> Bool -> State

here is the problem...

I don't know how to get to know whether a person is belong to members.

I'd like to find it through a person's name.

Can you suggest any examples??

Sincerely,

Jeon 

 

   

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