diff --git a/package.yaml b/package.yaml
index 67426df..043e986 100644
--- a/package.yaml
+++ b/package.yaml
@@ -22,6 +22,7 @@ default-extensions:
   - DerivingStrategies
   - ImportQualifiedPost
   - NoImplicitPrelude
+  - OverloadedRecordDot
   - OverloadedStrings
   - StandaloneKindSignatures
   - RoleAnnotations
diff --git a/scalie.cabal b/scalie.cabal
index f4acf24..fab9b99 100644
--- a/scalie.cabal
+++ b/scalie.cabal
@@ -39,6 +39,7 @@ library
       DerivingStrategies
       ImportQualifiedPost
       NoImplicitPrelude
+      OverloadedRecordDot
       OverloadedStrings
       StandaloneKindSignatures
       RoleAnnotations
@@ -61,6 +62,7 @@ executable scalie-exe
       DerivingStrategies
       ImportQualifiedPost
       NoImplicitPrelude
+      OverloadedRecordDot
       OverloadedStrings
       StandaloneKindSignatures
       RoleAnnotations
@@ -87,6 +89,7 @@ test-suite scalie-test
       DerivingStrategies
       ImportQualifiedPost
       NoImplicitPrelude
+      OverloadedRecordDot
       OverloadedStrings
       StandaloneKindSignatures
       RoleAnnotations
diff --git a/src/Data/Map/Implicit.hs b/src/Data/Map/Implicit.hs
index 7996c15..b4b367e 100644
--- a/src/Data/Map/Implicit.hs
+++ b/src/Data/Map/Implicit.hs
@@ -6,7 +6,7 @@
 {-# LANGUAGE StandaloneDeriving #-} -- derive Eq
 -- | A Map that derives the keys for the mapping from the items.
 
-module Data.Map.Implicit (ImplicitMap(), get, ImplicitKeyOf(..), empty, fromList) where
+module Data.Map.Implicit (ImplicitMap(), get, ImplicitKeyOf(..), empty, fromList, lookup) where
 import Data.Kind (Type, Constraint)
 import Data.Map (Map)
 import Text.Show (Show (show))
@@ -21,6 +21,7 @@ import Data.Ord (Ord)
 import Data.Eq (Eq)
 import Test.QuickCheck.Arbitrary (Arbitrary (arbitrary))
 import Test.QuickCheck.Gen (Gen)
+import Data.Maybe (Maybe)
 
 -- | This map will use the 'ImplicitKeyOf' class to compute the keys of the values.
 
@@ -61,10 +62,20 @@ class ImplicitKeyOf v where
   type KeyType v :: Type
   keyOf :: v -> KeyType v
 
+-- | The empty map
+
 empty :: ImplicitMap v
 empty = ImplicitMap Map.empty
 
+-- | Build from a List of values, keys will be inferred using 'ImplicitKeyOf'.
+-- If multiple values have the same key, the last one specified in the list will be used.
+
 fromList :: (ImplicitKeyOf v, Ord (KeyType v)) => [v] -> ImplicitMap v
 fromList = List.map (keyOf &&& id)
   >>> Map.fromList
   >>> ImplicitMap
+
+-- | Retrieve the value associated with its implicit key from the map.
+
+lookup :: Ord (KeyType a) => KeyType a -> ImplicitMap a -> Maybe a
+lookup k m = Map.lookup k (get m)
diff --git a/src/Language/Scalie/Ast/Definition.hs b/src/Language/Scalie/Ast/Definition.hs
index 7ebc156..b8ebb3d 100644
--- a/src/Language/Scalie/Ast/Definition.hs
+++ b/src/Language/Scalie/Ast/Definition.hs
@@ -3,6 +3,8 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE OverloadedRecordDot #-}
 module Language.Scalie.Ast.Definition (Definition(..)) where
 
 import Data.Kind (Type)
@@ -22,6 +24,9 @@ import Data.Text qualified as Text
 import Control.Category (Category((.)))
 import Test.QuickCheck.Modifiers (UnicodeString(getUnicodeString))
 import Data.Functor (Functor)
+import Language.Scalie.Ast.Provenance (Provenance (value))
+import Data.Functor.Identity (Identity)
+import Data.Maybe (Maybe)
 
 -- | The definition of a value or a function (which is also a value)
 --
@@ -55,9 +60,19 @@ deriving stock instance (Show (f Expression), Show (f Scalie.Domain.Type), Show
 deriving stock instance (Read (f Expression), Read (f Scalie.Domain.Type), Read (f Text)) => Read (Definition f)
 deriving stock instance (Eq (f Expression)  , Eq (f Scalie.Domain.Type)  , Eq (f Text))   => Eq (Definition f)
 
-instance ImplicitKeyOf (Definition f) where
-  type KeyType (Definition f) = f Text
-  keyOf :: Definition f -> KeyType (Definition f)
+instance ImplicitKeyOf (Definition (Provenance a)) where
+  type KeyType (Definition (Provenance a)) = Text
+  keyOf :: Definition (Provenance a) -> KeyType (Definition (Provenance a))
+  keyOf = (.name.value)
+
+instance ImplicitKeyOf (Definition Identity) where
+  type KeyType (Definition Identity) = Identity Text
+  keyOf :: Definition Identity -> KeyType (Definition Identity)
+  keyOf = name
+
+instance ImplicitKeyOf (Definition Maybe) where
+  type KeyType (Definition Maybe) = Maybe Text
+  keyOf :: Definition Maybe -> KeyType (Definition Maybe)
   keyOf = name
 
 instance (Functor f, Arbitrary (f UnicodeString), Arbitrary (f Scalie.Domain.Type), Arbitrary (f Expression)) => Arbitrary (Definition f) where
diff --git a/src/Language/Scalie/Bytecode/Instruction.hs b/src/Language/Scalie/Bytecode/Instruction.hs
index 493f9a5..e15156c 100644
--- a/src/Language/Scalie/Bytecode/Instruction.hs
+++ b/src/Language/Scalie/Bytecode/Instruction.hs
@@ -5,7 +5,11 @@ import Data.Kind (Type)
 import Text.Show (Show)
 import Text.Read (Read)
 import Data.Eq (Eq)
+import Prelude (Integer) -- this is apparently the only safe way to import 'Integer'
+import Data.Word (Word8)
 
 type Instruction :: Type
 data Instruction
+  = PushInteger Integer
+  | ReturnValues Word8
   deriving stock (Show, Read, Eq)
diff --git a/src/Language/Scalie/Bytecode/Object/Builder.hs b/src/Language/Scalie/Bytecode/Object/Builder.hs
index fcd41ef..c75cd33 100644
--- a/src/Language/Scalie/Bytecode/Object/Builder.hs
+++ b/src/Language/Scalie/Bytecode/Object/Builder.hs
@@ -7,6 +7,7 @@ import Language.Scalie.Bytecode.Object qualified as Bytecode
 import Data.Functor (Functor)
 import Control.Applicative (Applicative (pure, (<*>)))
 import Control.Monad (Monad ((>>=)))
+import Prelude (undefined)
 
 type Builder :: Type -> Type
 type role Builder representational
@@ -25,4 +26,4 @@ instance Monad Builder where
 
 
 runBuilder :: Builder a -> (Bytecode.Object, a)
-runBuilder = _
+runBuilder = undefined
diff --git a/src/Language/Scalie/Compiler/Bytecode.hs b/src/Language/Scalie/Compiler/Bytecode.hs
index 8d95b9c..50a30ae 100644
--- a/src/Language/Scalie/Compiler/Bytecode.hs
+++ b/src/Language/Scalie/Compiler/Bytecode.hs
@@ -1,16 +1,37 @@
-{-# LANGUAGE Safe #-}
-module Language.Scalie.Compiler.Bytecode (EntryPoint, compile) where
-import Language.Scalie.Ast.Module (Module)
+{-# LANGUAGE Trustworthy #-} -- uses vector operations
+{-# LANGUAGE OverloadedRecordDot #-}
+module Language.Scalie.Compiler.Bytecode (EntryPoint, compile, CompilationError(..)) where
+import Language.Scalie.Ast.Module (Module (definitions))
 import Data.Text (Text)
-import Language.Scalie.Ast.Provenance (Provenance)
+import Language.Scalie.Ast.Provenance (Provenance (value, Provenance, source))
 import Language.Scalie.Ast.Provenance.SourceLocation (SourceLocation)
 import Language.Scalie.Bytecode.Object qualified as Bytecode
 import Data.Kind (Type)
+import Data.Either (Either (Left, Right))
+import Data.Vector qualified as Vector
+import Control.Category ((.))
+import Data.Function (($))
+import Data.Functor ((<$>))
+import Data.Map.Implicit qualified as ImplicitMap
+import Data.Maybe (Maybe(Nothing, Just))
+import Language.Scalie.Ast.Definition (Definition(body, name))
+import Language.Scalie.Ast.Expression (Expression(RawInt))
+import Language.Scalie.Bytecode.Instruction qualified as Instruction
 
 -- | The name of the entrypoint function
 
 type EntryPoint :: Type
 type EntryPoint = Text
 
-compile :: Module (Provenance SourceLocation) -> EntryPoint -> Bytecode.Object
-compile = _
+type CompilationError :: Type
+newtype CompilationError = NameNotFound Text
+
+compile :: Module (Provenance SourceLocation) -> EntryPoint -> Either CompilationError Bytecode.Object
+compile mod entry = let
+  topLevelDefinitions = mod.definitions.value
+  in Bytecode.Object . Vector.fromList <$> case ImplicitMap.lookup entry topLevelDefinitions of
+    Nothing -> Left $ NameNotFound entry
+    Just def -> Right
+      [ (\(RawInt i) -> Instruction.PushInteger i) <$> def.body
+      , Provenance def.name.source (Instruction.ReturnValues 1)
+      ]