Write You a Haskell Stephen Diehl

Datatypes
Constructors for datatypes come in two flavors: sum types and product types.
A sum type consists of multiple options of type constructors under the same type. e two cases can be
used at all locations the type is specified, and are discriminated using pattern matching.
data Sum = A Int | B Bool
A product type combines multiple typed fields into the same type.
data Prod = Prod Int Bool
Records are a special product type that, in addition to generating code for the constructors, generates a
special set of functions known as selectors which extract the values of a specific field from the record.
data Prod = Prod { a :: Int , b :: Bool }
-- a :: Prod -> Int
-- b :: Prod -> Bool
Sums and products can be combined.
data T1
= A Int Int
| B Bool Bool
e fields of a datatype may be parameterized, in which case the type depends on the specific types the
fields are instantiated with.
data Maybe a = Nothing | Just a
Values
A list is a homogeneous, inductively defined sum type of linked cells parameterized over the type of its
values.
data List a = Nil | Cons a (List a)
a = [1,2,3]
a = Cons 1 (Cons 2 (Cons 3 Nil))
List have special value-level syntax:
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