create a list of objects of different type in Haskell?

Question

I have to create a function that receives this to work with the list parameters

check [c, (x,y,z), c, (x,y,z), ..., c, (x,y,z)]

where c is a integer and (x,y,z) a tuple

but I don't know how to implement the function

If each c is followed by a 3-tuple, why not [(c, (x, y, z)), (c, (x,y,z)), ...]? — willeM_ Van Onsem
– willeM_ Van Onsem, Commented Oct 27, 2020 at 17:48
You can't really have heterogenous lists like that. Either use a nested tuple if they come in pairs, or a discriminating union type like Either Integer YourTuple — that other guy
– that other guy, Commented Oct 27, 2020 at 17:52
Seeing as you can't create such a list, it seems unlikely that you have to create a function that receives them. (This looks like an XY problem.) — molbdnilo
– molbdnilo, Commented Oct 27, 2020 at 17:53

OpenAI was the last straw · Accepted Answer · 2020-10-27 17:55:47Z

1

This is not possible. A list can only contain values of a single type. You could make a [Either Integer (Integer, Integer, Integer)], in which case your list would look like [Left c1, Right (x1, y1, z1), Left c2, Right (x2, y2, z2)], but this isn't very satisfying, will likely be difficult to work with, and can't be enforced by the type system. Remember that the more we allow the type checker to enforce, the less likely we are to run into unexpected values down the line.

Instead, you should consider bracketing the mismatched types into a list of pairs [(Integer, (Integer, Integer, Integer))], which would make the list look like [(c1, (x1, y1, z1)), (c2, (x2, y2, z2))].

answered Oct 27, 2020 at 17:55

OpenAI was the last straw

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