PgsqlTest.hs

{-# LANGUAGE OverloadedStrings, DeriveDataTypeable, ScopedTypeVariables #-}

import Database.PostgreSQL.Simple
import Database.PostgreSQL.Simple.FromRow
import Database.PostgreSQL.Simple.FromField

import Data.Typeable

import Control.Applicative

data Location = Location { latitude  :: Double
                         , longitude :: Double }
                deriving (Eq, Typeable, Show)

instance FromField Location where
  fromField f dat = fmap (uncurry Location) $ fromField f dat

copts :: ConnectInfo  
copts = defaultConnectInfo { connectUser = "dan", connectDatabase = "test" }  

main = do
  c <- connect copts
  x :: [Only Location] <- query_ c "select loc from markers"
  print x
  close c