-- my Interpreter file

module HReal.Server.Interpreter where

import HReal.Core.World
import HReal.Core.History
import Language.Haskell.Interpreter as I

type Modification = History -> Either Constraint World

interpret :: String -> IO (Either InterpreterError Modification)
interpret source = runInterpreter $ do
    setImports [ "Prelude"
               , "Data.Int"
               , "Data.Map"
               , "Data.Set"
               , "HReal.Core.Prelude" ]
    I.interpret source (as :: Modification)

-- HReal.Core.Prelude file

module HReal.Core.Prelude
       ( module HReal.Core.World
       , module HReal.Core.History
       , module HReal.Core.Vertex

       ) where

import HReal.Core.World
import HReal.Core.History
import HReal.Core.Vertex

*Main> do; Left c <- I.interpret "undefined"; print c
WontCompile [GhcError {errMsg = "Not in scope: type constructor or class `HReal.Core.World.World'"},GhcError {errMsg = "Not in scope:\n  type constructor or class `HReal.Core.World.Constraint'"},GhcError {errMsg = "Not in scope: type constructor or class `HReal.Core.World.World'"}]

-- A.hs
module A (module B, b) where
import B
b :: B
b = 0
-- B.hs
module B where type B = Int
-- Main.hs
module Main where
import A
import Language.Haskell.Interpreter
main :: IO ()
main = (print =<<) . runInterpreter $ do
  loadModules [ "A" ]  -- this is important for success
  setImports [ "Prelude", "A" ]
  interpret "b" (as :: B)

module Main where

import Language.Haskell.Interpreter
import Language.Haskell.Interpreter.Unsafe

import Data.Typeable as T
import Data.Typeable.Internal
import GHC.Fingerprint.Type

main = failure >> success

test t = (print =<<) . runInterpreter $ do
  setImports [ "Prelude" ]
  interpret "1/5" t

failure = test (as :: Rational)

success = test (as :: Q)

newtype Q = Q Rational
instance Typeable Q where typeOf _ = TypeRep (Fingerprint 0 0) (T.mkTyCon "Rational") []
instance Show Q where
  show (Q a) = show a
  showsPrec n (Q a) = showsPrec n a


{-

Left (WontCompile [GhcError {errMsg = "Not in scope: type constructor or class `Ratio'"}])
Right (1 % 5)

-}