Re: [Haskell-beginners] Structural restrictions in type constructor

I would think that it is not possible to use types to constrain the values of data. I.e. type signature can be only used to constraint types, not values. But I am a beginner myself, so see if someone more experienced can shed light here. Martin Matt Williams:

Dear All,

I wonder if/ how this is possible?

I have a constructor which takes 2 pairs of type t).

However, I want to ensure that the pairs are matched:

MyP = MyP (t, t) (t, t)

But where the first pair contains the same elements as the second, but reversed in order.

Any help much appreciated.

BW, Matt

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