diff --git a/flap/src/hopix/hopixInterpreter.ml b/flap/src/hopix/hopixInterpreter.ml
index faa02e8..d0f6ac2 100644
--- a/flap/src/hopix/hopixInterpreter.ml
+++ b/flap/src/hopix/hopixInterpreter.ml
@@ -343,13 +343,20 @@ and definition runtime d =
 
 and value_definition runtime = function
   | SimpleValue (id, _, expr) ->
-    (* TODO: Ici il faut associer l'ID et l'expression
-     * => Retourner l'environnement modifié *)
-    runtime
-  | RecFunctions rf ->
-    (* TODO: Ici faut ajouter les noms des fonctions à l'environnement
+    (* Ici on associe l'ID et l'expression
+     * => Retourne l'environnement modifié *)
+    let env' =
+      Environment.bind
+        runtime.environment
+        id.value
+        (expression' runtime.environment runtime.memory expr)
+    in
+    { runtime with environment = env' }
+  | RecFunctions _rf ->
+    (* Ici on ajoute les noms des fonctions à l'environnement
      * pour qu'elles puissent s'appeller dans leur corps de fonction
-     * => Il faut retourner un environnement modifié *)
+     * => Retourne l'environnement modifié *)
+    (* TODO *)
     runtime
 
 and expression' environment memory e =
@@ -360,9 +367,64 @@ and expression' environment memory e =
     E, M ⊢ e ⇓ v, M'
 
     and E = [runtime.environment], M = [runtime.memory]. *)
-and expression _ environment memory =
-  (* TODO *)
-  failwith "Students! This is your job!"
+and expression _pos environment _memory = function
+  | Literal l -> literal_expression l.value
+  | Variable (id, _) ->
+    (* On cherche l'id dans l'environnement *)
+    Environment.lookup id.position id.value environment
+  | Tagged _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Tagged)!"
+  | Record _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Record)!"
+  | Field _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Field)!"
+  | Tuple _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Tuple)!"
+  | Sequence _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Sequence)!"
+  | Define _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Define)!"
+  | Fun _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Fun)!"
+  | Apply _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Apply)!"
+  | Ref _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Ref)!"
+  | Assign _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Assign)!"
+  | Read _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Read)!"
+  | Case _ ->
+    (* TODO *)
+    failwith "Students! This is your job (Case)!"
+  | IfThenElse _ ->
+    (* TODO *)
+    failwith "Students! This is your job (IfThenElse)!"
+  | While _ ->
+    (* TODO *)
+    failwith "Students! This is your job (While)!"
+  | For _ ->
+    (* TODO *)
+    failwith "Students! This is your job (For)!"
+  | TypeAnnotation _ ->
+    (* On ignore le type car on interprète *)
+    VUnit
+
+and literal_expression = function
+  | LInt n -> VInt n
+  | LChar c -> VChar c
+  | LString s -> VString s
 
 (** This function returns the difference between two runtimes. *)
 and extract_observable runtime runtime' =