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jlam55555/TypeInferenceExample.hs

Created September 24, 2021 18:52
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TypeInferenceExample.hs
{-# LANGUAGE DeriveGeneric, GADTs, OverloadedStrings, FlexibleContexts, FlexibleInstances, TypeFamilies, TypeApplications, DeriveAnyClass, StandaloneDeriving, TypeSynonymInstances, MultiParamTypeClasses, ImpredicativeTypes #-}
-- following tutorial from https://haskell-beam.github.io/beam/tutorials/tutorial1/
-- minimal example for https://stackoverflow.com/q/69319523/2397327
-- need to have beam-core and beam-sqlite packages installed
import Database.Beam.Sqlite
import Database.SQLite.Simple
-- version 1
getDb = open "shoppingcart1.db"
runDebug conn = runBeamSqliteDebug putStr conn
runDebugInDb actions = do conn <- getDb
runDebug conn actions
-- version 2
-- dbFile = "shoppingcart1.db"
-- getDb = open dbFile
-- runDebug conn = runBeamSqliteDebug putStr conn
-- -- runDebugInDb :: SqliteM a -> IO a
-- runDebugInDb actions = do conn <- getDb
-- runDebug conn actions
-- running version 1:
-- λ> :t (getDb, runDebug, runDebugInDb)
-- (getDb, runDebug, runDebugInDb)
-- :: (IO Connection, Connection -> SqliteM a -> IO a,
-- SqliteM b -> IO b)
-- running version 2:
-- λ> :t (getDb, runDebug, runDebugInDb)
-- (getDb, runDebug, runDebugInDb)
-- :: (IO Connection, Connection -> SqliteM a -> IO a,
-- SqliteM ghc-prim-0.6.1:GHC.Types.Any
-- -> IO ghc-prim-0.6.1:GHC.Types.Any)
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