Feature repl

mulang.cabal

@@ -108,6 +108,7 @@ library
     Language.Mulang.Edl.Parser
     Language.Mulang.Interpreter
     Language.Mulang.Interpreter.Internals
+    Language.Mulang.Interpreter.Repl
     Language.Mulang.Interpreter.Runner
     Language.Mulang.Transform.Normalizer
     Language.Mulang.Transform.Renamer

spec/ReplSpec.hs

@@ -0,0 +1,33 @@
+module ReplSpec (spec) where
+
+import           Test.Hspec
+import           Language.Mulang.Parsers.JavaScript
+import           Language.Mulang.Interpreter.Repl
+import           Language.Mulang.Interpreter.Internals (Value (..))
+
+spec :: Spec
+spec = do
+  describe "repl" $ do
+    let s0 = newSession js
+    it "evals and returns" $ do
+      (r1, _) <- repl "1" s0
+      r1 `shouldBe` (MuNumber 1)
+
+    it "can eval multiple statements and return" $ do
+      (r1, s1) <- repl "var x = 1" s0
+      r1 `shouldBe` (MuNumber 1)
+
+      (r2, s2) <- repl "x + 3" s1
+      r2 `shouldBe` (MuNumber 4)
+
+      (_, s3) <- repl "function double(x) { return x * 2 }" s2
+      (r4, _) <- repl "double(x)" s3
+      r4 `shouldBe` (MuNumber 2)
+
+    it "can save state" $ do
+      (_, s1) <- repl "function succ(x) { return x + 1 }" s0
+      (_, s2) <- repl "function pred(x) { return x - 1 }" s1
+
+      (r, _) <- repl "succ(succ(pred(10)))" (reload s2)
+      r `shouldBe` (MuNumber 11)
+

src/Language/Mulang/Interpreter/Repl.hs

@@ -0,0 +1,48 @@
+module Language.Mulang.Interpreter.Repl (
+  Session (..),
+  newSession,
+  repl,
+  dump,
+  load,
+  reload) where
+
+import           Language.Mulang.Ast (Expression)
+import           Language.Mulang.Interpreter (eval)
+import           Language.Mulang.Interpreter.Internals (Value, Reference (..), ExecutionContext (..), defaultContext)
+
+import qualified Data.Map as Map
+import           Data.Map ((!))
+
+type SessionState = ([(Int, Value)], [Int])
+type Language = (String -> Expression)
+
+data Session = Session { language :: Language, context :: ExecutionContext }
+
+newSession :: Language -> Session
+newSession language = Session language defaultContext
+
+repl :: String -> Session -> IO (Value, Session)
+repl line session = do
+  (ref, newContext) <- eval (context session) (language session line)
+  return (globalObjects newContext ! ref, session { context = newContext } )
+
+dump :: Session -> SessionState
+dump (Session _ (ExecutionContext globals scopes _ _ _ )) = (dumpGlobals globals, dumpScopes scopes)
+  where
+    dumpGlobals = Map.toList . Map.mapKeys asInt
+    dumpScopes = map asInt
+
+load :: Language -> SessionState -> Session
+load language (globalsState, scopesState) = Session language (defaultContext { globalObjects = loadGlobals globalsState, scopes = loadScopes scopesState } )
+  where
+    loadGlobals = Map.mapKeys fromInt . Map.fromList
+    loadScopes  = map fromInt
+
+reload :: Session -> Session
+reload s@(Session l _) = load l (dump s)
+
+fromInt :: Int -> Reference
+fromInt = Reference
+
+asInt :: Reference -> Int
+asInt (Reference i) = i