Given that my Purescript program contains different types representing items that can be exchanged, for example Vegetable, Milk, Meat etc., what is the best way to represent a ledger data-structure that tracks the exchanges between participants? To simplify we can represent participants as type Participant = Int.
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z1naOK9nu8iY5A
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1How would you represent the data in any other language? – Phil Freeman Dec 04 '16 at 20:32
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How do you represent heterogeneous types in a common `Entry` structure? – z1naOK9nu8iY5A Dec 08 '16 at 14:38
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1Using a sum type perhaps. – Phil Freeman Dec 09 '16 at 02:37
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You can use purescript-variant for open sums.
type Ledger products = Array (Entry products)
type Entry products =
{ date ∷ DateTime
, product ∷ Variant products
, unitPrice ∷ Int
, quantity ∷ Int
}
A Ledger type can then be instantiated for a particular set of products, such as Ledger (milk ∷ Milk, vegetable ∷ Vegetable, meat ∷ Meat).
erisco
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