jjant

myCoolFunction : Int -> Int
myCoolFunction a =
    -- Calls the JS `addTwo` function.
    jsCall "addTwo" a


main =
    myCoolFunction 3
        |> String.fromInt
        |> Html.text

jjant

data FreeMonoid t
  = Zero
  | Combine t (FreeMonoid t)

jjant

data FreeMonoid1 t
  = Zero
  | Val t
  | Combine (FreeMonoid1 t) (FreeMonoid1 t)

jjant

isAdmin :: FreeMonoid (String, Bool) -> Bool
isAdmin perms = interpret True (\(_, perm) rest -> perm && rest) perms

isPowerUser :: FreeMonoid (String, Bool) -> Bool
isPowerUser perms = interpret False (\(_, perm) rest -> perm || rest) perms

isRegularUser :: FreeMonoid (String, Bool) -> Bool
isRegularUser perms = not (isPowerUser perms)

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interpret :: b -> (a -> b -> b) -> FreeMonoid a -> b
interpret myZero myCombine Zero = myZero
interpret myZero myCombine (Combine a rest) =
  a `myCombine` (interpret myZero myCombine rest) -- a `Combine` (b `Combine` Zero) -> a `myCombine` (b `myCombine` myZero)

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zero :: FreeMonoid t
zero = Zero

(<>) :: FreeMonoid t -> FreeMonoid t -> FreeMonoid t
Zero <> x = x -- Left identity
x    <> Zero = x -- Right identity
(Combine t1 rest1) <> x =
  -- `(a <> b) <> x` is represented as `a <> (b <> x)`
  Combine t1 (rest1 <> x)

jjant

employeeAppToEmployeeCount : EmployeeApp -> EmployeeWithCount
employeeAppToEmployeeCount employeeApp =
    map (\employees -> List.length employees) employeeApp

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map : (a -> b) -> Employee a -> Employee b
map f (Employee sharedData a) =
    Employee sharedData (f a)


replace : b -> Employee a -> Employee b
replace b =
    map (\_ -> b)

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type alias Id =
    Int


type Employee1
    = Employee1
        { id : Id
        , name : String
        , age : Int
        , employees : List Employee1

jjant

type EmployeeFromDb1
    = EmployeeFromDb1
        { id : Id
        , name : String
        , age : Int
        , employerId : Id
        }