Simple "user" modelling examples in Clojure, Haskell & Scala.

model.clj

(ns model
  (:require [clojure.spec.alpha :as s]))

(s/def :user/first-name string?)
(s/def :user/last-name string?)
(s/def :user/full-name string?)
(s/def ::user (s/keys :req [:user/first-name
                            :user/last-name]))

(s/fdef full-name
  :args (s/cat :user ::user)
  :ret :user/full-name)

(defn full-name [{:user/keys [first-name last-name]}]
  (str first-name " " last-name))

(defn -main [& args]
  (let [u #:user{:first-name "You"
                 :last-name "Watanabe"}]
    (println (str "user: " u))
    (println (str "user's full name: " (full-name u)))))

Model.hs

{-# LANGUAGE NamedFieldPuns #-}

module Model where

data User = User { firstName :: !String
                 , lastName  :: !String
                 }
            deriving Show

fullName :: User -> String
fullName User{firstName, lastName} = firstName ++ " " ++ lastName

main :: IO ()
main = do
    let u = User { firstName = "You", lastName = "Watanabe"}
    putStrLn $ "user: " ++ show u
    putStrLn $ "user's full name: " ++ fullName u

Model.scala

case class User(firstName: String, lastName: String) {
  val fullName = s"$firstName $lastName"
}

object Model extends App {
  val u = User(firstName = "You", lastName = "Watanabe")
  println(s"user: $u")
  println(s"user's full name: ${u.fullName}")
}

Execution results:

$ clj -Sdeps '{:paths ["."]}' -m model
user: #:user{:first-name "You", :last-name "Watanabe"}
user's full name: You Watanabe
$ runghc Model.hs
user: User {firstName = "You", lastName = "Watanabe"}
user's full name: You Watanabe
$ scala Model.scala
user: User(You,Watanabe)
user's full name: You Watanabe