diff --git a/grin/grin.cabal b/grin/grin.cabal
index 6e40679f..0859c533 100644
--- a/grin/grin.cabal
+++ b/grin/grin.cabal
@@ -70,6 +70,7 @@ library
     AbstractInterpretation.IR
     AbstractInterpretation.CodeGen
     AbstractInterpretation.Reduce
+    Frontend.FromSTG
     VarGen
     Pipeline
     Assertions
@@ -109,7 +110,8 @@ library
     hspec,
     extra,
     logict,
-    QuickCheck
+    QuickCheck,
+    ghc
   default-language:    Haskell2010
 
 executable grin
diff --git a/grin/src/Frontend/FromSTG.hs b/grin/src/Frontend/FromSTG.hs
new file mode 100644
index 00000000..5439de64
--- /dev/null
+++ b/grin/src/Frontend/FromSTG.hs
@@ -0,0 +1,122 @@
+{-# LANGUAGE LambdaCase, TupleSections #-}
+module Frontend.FromSTG where
+
+import Text.Printf
+
+-- GHC
+import StgSyn
+import Id
+import Name as GHC
+import DynFlags
+import Outputable
+import Literal
+import DataCon
+
+-- Grin
+import Grin
+
+import Control.Monad as M
+import Control.Monad.State
+
+type CG = State Env
+
+data Env
+  = Env
+  { dflags  :: DynFlags
+  }
+
+getDFlags :: CG DynFlags
+getDFlags = gets dflags
+
+genName :: Id -> CG String
+genName = undefined
+
+pprM :: Outputable a => a -> CG String
+pprM a = flip showPpr a <$> gets dflags
+
+emit = undefined
+
+convertLit :: Literal -> CG Lit
+convertLit = \case
+  MachInt     i -> pure $ LInt64 $ fromIntegral i
+  MachInt64   i -> pure $ LInt64 $ fromIntegral i
+  MachWord    w -> pure $ LWord64 $ fromIntegral w
+  MachWord64  w -> pure $ LWord64 $ fromIntegral w
+  MachFloat   f -> pure $ LFloat $ realToFrac f
+  MachDouble  f -> pure $ LFloat $ realToFrac f
+  lit -> error . printf "unsupported literal %s" <$> pprM lit
+
+visitArg :: StgArg -> CG Val
+visitArg = \case
+  StgVarArg id  -> Var <$> genName id
+  StgLitArg lit -> Lit <$> convertLit lit
+
+visitRhs :: Id -> StgRhs -> CG ()
+visitRhs id rhs = case rhs of
+  StgRhsCon _ dataCon args -> pure () -- TODO
+  StgRhsClosure _ _ freeVars _ _ args body -> do
+    {-
+      TODO:
+        - add def to globals with the right argumentum list
+        - generate the body
+    -}
+    visitExpr body
+    pure ()
+
+visitBinding :: StgBinding -> CG ()
+visitBinding = \case
+  StgNonRec id stgRhs -> visitRhs id stgRhs
+  StgRec bindings     -> mapM_ (uncurry visitRhs) bindings
+
+visitExpr :: StgExpr -> CG ()
+visitExpr = \case
+  StgApp id args                  -> SApp <$> genName id <*> mapM visitArg args >>= emit
+  StgOpApp op args _ty            -> SApp <$> genOpName op <*> mapM visitArg args >>= emit
+  StgConApp dataCon args          -> ConstTagNode <$> genTag dataCon <*> mapM visitArg args >>= emit . SReturn
+  StgLit literal                  -> SReturn . Lit <$> convertLit literal >>= emit
+  StgTick _ expr                  -> visitExpr expr
+  StgLet binding expr             -> visitBinding binding >> visitExpr expr -- TODO: generate local or global bind
+  StgLetNoEscape _ _ binding expr -> visitBinding binding >> visitExpr expr -- TODO: generate local or global bind
+  StgCase expr _ _ result _ _ alts  -> undefined -- TODO: construct case expression
+  expr -> error . printf "unsupported expr %s" <$> pprM expr
+
+genOpName :: StgOp -> CG String
+genOpName = \case
+  StgPrimOp op      -> pprM op -- TODO
+  StgPrimCallOp op  -> pprM op -- TODO
+  StgFCallOp op _   -> pprM op -- TODO
+
+genTag :: DataCon -> CG Tag
+genTag dataCon = Tag C <$> pprM dataCon
+
+{-
+-- If you edit this type, you may need to update the GHC formalism
+-- See Note [GHC Formalism] in coreSyn/CoreLint.hs
+data AltCon
+  = DataAlt DataCon   --  ^ A plain data constructor: @case e of { Foo x -> ... }@.
+                      -- Invariant: the 'DataCon' is always from a @data@ type, and never from a @newtype@
+
+  | LitAlt  Literal   -- ^ A literal: @case e of { 1 -> ... }@
+                      -- Invariant: always an *unlifted* literal
+                      -- See Note [Literal alternatives]
+
+  | DEFAULT           -- ^ Trivial alternative: @case e of { _ -> ... }@
+   deriving (Eq, Ord, Data, Typeable)
+
+type GenStgAlt bndr occ
+  = (AltCon,            -- alts: data constructor,
+     [bndr],            -- constructor's parameters,
+     [Bool],            -- "use mask", same length as
+                        -- parameters; a True in a
+                        -- param's position if it is
+                        -- used in the ...
+     GenStgExpr bndr occ)       -- ...right-hand side.
+
+data DataCon
+  = MkData {
+        dcName    :: Name,      -- This is the name of the *source data con*
+                                -- (see "Note [Data Constructor Naming]" above)
+        dcUnique :: Unique,     -- Cached from Name
+        dcTag    :: ConTag,     -- ^ Tag, used for ordering 'DataCon's
+
+-}
\ No newline at end of file
diff --git a/todo.just-to-practice b/todo.just-to-practice
index f672d003..c8213766 100644
--- a/todo.just-to-practice
+++ b/todo.just-to-practice
@@ -142,9 +142,10 @@ M: vectorisation as conversion to tagged unions
 T: new approach: optimise high level grin ; implement some optimisations
 W: copy propagation, constant propagation, dead procedure elimination, use hylo to skip operations, dead variable elimination
 T: common sub-expression elimination, inlining
-F:
-S:
-S:
+F: stg
+S: weekend
+S: stg to grin
+M: add source code links to schema tables, stg to grin
 
 - linter that check all possible alternatives are handled by case alternatives
 - dead code elimination using HPTResult ; empty type is dead code i.e. {}