Question

I am currently writing my own structurewhich can handle ints and strings at the same time:

Something like

data Collection = One Int | Two String | Three(Collection)(Collection)

However, I was trying to write a function which could convert my structure into a list.

Am I right in thinking this is impossible because, by default doing:

[1,2,”test”]

in the console doesn’t work and therefore my function is bound to always fail?

Answer 1

You should probably just define

type Collection = [Either Int String]

Then, instead of doing

l = [1,2,"test"]

you can do

l :: Collection
l = [Left 1, Left 2, Right "test"]

If you want more than two types, you’ll need to define your own member type. So you would do something like this aswell

data MemberType = MyInt Int | MyString String | MyFloat Float deriving Show
type Collection = [MemberType]
l :: Collection
l = [MyInt 1, MyInt 2, MyString "test", MyFloat 2.2]

The deriving Show isn’t necessary, but it’s nice to be able to simply do print l to print the list in a nice way.