Finally started to use something fancy (Data.Aeson)

First time aeson user. The magic part is ToJSON/FromJSON instance. Knowing how generics works in Haskell, one could intuitively expect empty ToJSON and FromJSON instance to work as is (no need to write any specialization to serialize/de-serialize ADT) and that will be the discipline I would choose when define APIs.

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DeriveGeneric #-}
import qualified Data.ByteString.Lazy as L
import qualified Data.Text as Text
import Data.Text(Text)

import Data.Aeson
import GHC.Generics

data Patient = Patient {
    firstName :: Text
  , lastName :: Text
  , emailAddress :: Text
  , birthDate :: Text
  , latestBloodPressureDate :: Text
  , systolic :: Int
  , diastolic :: Int
  } deriving (Generic, Show)

instance ToJSON Patient where
instance FromJSON Patient where

patients :: L.ByteString -> Maybe [Patient]
patients = decode

main = L.getContents >>= print . patients