diff --git a/Makefile_happysrcs b/Makefile_happysrcs
index e0dc43e..1d32855 100644
--- a/Makefile_happysrcs
+++ b/Makefile_happysrcs
@@ -8,8 +8,8 @@ CABAL_BUILD = dist-newstyle/build/x86_64-osx/ghc-9.6.2/rlp-0.1.0.0/build
 
 all: parsers lexers
 
-parsers: $(CABAL_BUILD)/Rlp/Parse.hs
-lexers: $(CABAL_BUILD)/Rlp/Lex.hs
+parsers: $(CABAL_BUILD)/Rlp/Parse.hs $(CABAL_BUILD)/Core/Parse.hs
+lexers: $(CABAL_BUILD)/Rlp/Lex.hs $(CABAL_BUILD)/Core/Lex.hs
 
 $(CABAL_BUILD)/Rlp/Parse.hs: $(SRC)/Rlp/Parse.y
 	$(HAPPY) $(HAPPY_OPTS) $< -o $@
@@ -17,3 +17,9 @@ $(CABAL_BUILD)/Rlp/Parse.hs: $(SRC)/Rlp/Parse.y
 $(CABAL_BUILD)/Rlp/Lex.hs: $(SRC)/Rlp/Lex.x
 	$(ALEX) $(ALEX_OPTS) $< -o $@
 
+$(CABAL_BUILD)/Core/Parse.hs: $(SRC)/Core/Parse.y
+	$(HAPPY) $(HAPPY_OPTS) $< -o $@
+
+$(CABAL_BUILD)/Core/Lex.hs: $(SRC)/Core/Lex.x
+	$(ALEX) $(ALEX_OPTS) $< -o $@
+
diff --git a/src/Compiler/JustRun.hs b/src/Compiler/JustRun.hs
index c3178f3..6a0d4ca 100644
--- a/src/Compiler/JustRun.hs
+++ b/src/Compiler/JustRun.hs
@@ -26,22 +26,23 @@ import Data.Function                    ((&))
 import GM
 ----------------------------------------------------------------------------------
 
--- justLexSrc :: String -> Either RlpcError [CoreToken]
+justLexSrc :: String -> Either [MsgEnvelope RlpcError] [CoreToken]
 justLexSrc s = lexCoreR (T.pack s)
              & fmap (map $ \ (Located _ _ _ t) -> t)
              & rlpcToEither
 
--- justParseSrc :: String -> Either RlpcError Program'
+justParseSrc :: String -> Either [MsgEnvelope RlpcError] Program'
 justParseSrc s = parse (T.pack s)
                & rlpcToEither
     where parse = lexCoreR >=> parseCoreProgR
 
--- justTypeCheckSrc :: String -> Either RlpcError Program'
+justTypeCheckSrc :: String -> Either [MsgEnvelope RlpcError] Program'
 justTypeCheckSrc s = typechk (T.pack s)
                    & rlpcToEither
     where typechk = lexCoreR >=> parseCoreProgR >=> checkCoreProgR
 
-rlpcToEither = undefined
-
-{-# WARNING rlpcToEither "unimpl" #-}
+rlpcToEither :: RLPC a -> Either [MsgEnvelope RlpcError] a
+rlpcToEither r = case evalRLPC def r of
+    (Just a,   _) -> Right a
+    (Nothing, es) -> Left es
 
diff --git a/src/Core/Parse.y b/src/Core/Parse.y
index a084ebf..b8a0cf3 100644
--- a/src/Core/Parse.y
+++ b/src/Core/Parse.y
@@ -98,6 +98,8 @@ ScDefs          : ScDef ';' ScDefs              { $1 : $3 }
 
 ScDef           :: { ScDef Name }
 ScDef           : Var ParList '=' Expr          { ScDef $1 $2 $4 }
+                -- hack to allow constructors to be compiled into scs
+                | Con ParList '=' Expr          { ScDef $1 $2 $4 }
 
 Type            :: { Type }
 Type            : Type1                         { $1 }