diff --git a/compiler/obc/obc.ml b/compiler/obc/obc.ml
index ed2d413..885454a 100644
--- a/compiler/obc/obc.ml
+++ b/compiler/obc/obc.ml
@@ -86,7 +86,7 @@ type method_def =
       m_inputs : var_dec list;
       m_outputs : var_dec list;
       m_locals : var_dec list;
-      m_body : act list; }
+      m_body : block; }
 
 type class_def =
     { cd_name : class_name;
diff --git a/compiler/obc/obc_mapfold.ml b/compiler/obc/obc_mapfold.ml
new file mode 100644
index 0000000..8c3debc
--- /dev/null
+++ b/compiler/obc/obc_mapfold.ml
@@ -0,0 +1,207 @@
+ (**************************************************************************)
+(*                                                                        *)
+(*  Heptagon                                                              *)
+(*                                                                        *)
+(*  Author : Marc Pouzet                                                  *)
+(*  Organization : Demons, LRI, University of Paris-Sud, Orsay            *)
+(*                                                                        *)
+(**************************************************************************)
+(* Generic mapred over Obc Ast *)
+open Misc
+open Global_mapfold
+open Obc
+
+type 'a obc_it_funs = {
+  exp:        'a obc_it_funs -> 'a -> Obc.exp -> Obc.exp * 'a;
+  edesc:      'a obc_it_funs -> 'a -> Obc.exp_desc -> Obc.exp_desc * 'a;
+  lhs:        'a obc_it_funs -> 'a -> Obc.lhs -> Obc.lhs * 'a;
+  lhsdesc:    'a obc_it_funs -> 'a -> Obc.lhs_desc -> Obc.lhs_desc * 'a;
+  act:        'a obc_it_funs -> 'a -> Obc.act -> Obc.act * 'a;
+  block:      'a obc_it_funs -> 'a -> Obc.block -> Obc.block * 'a;
+  var_dec:    'a obc_it_funs -> 'a -> Obc.var_dec -> Obc.var_dec * 'a;
+  var_decs:   'a obc_it_funs -> 'a -> Obc.var_dec list
+                                   -> Obc.var_dec list * 'a;
+  obj_dec:    'a obc_it_funs -> 'a -> Obc.obj_dec -> Obc.obj_dec * 'a;
+  obj_decs:   'a obc_it_funs -> 'a -> Obc.obj_dec list
+                                   -> Obc.obj_dec list * 'a;
+  method_def: 'a obc_it_funs -> 'a -> Obc.method_def -> Obc.method_def * 'a;
+  class_def:  'a obc_it_funs -> 'a -> Obc.class_def -> Obc.class_def * 'a;
+  const_dec:  'a obc_it_funs -> 'a -> Obc.const_dec -> Obc.const_dec * 'a;
+  type_dec:   'a obc_it_funs -> 'a -> Obc.type_dec -> Obc.type_dec * 'a;
+  tdesc:      'a obc_it_funs -> 'a -> Obc.tdesc -> Obc.tdesc * 'a;
+  program:    'a obc_it_funs -> 'a -> Obc.program -> Obc.program * 'a;
+  global_funs:'a Global_mapfold.global_it_funs }
+
+
+let rec exp_it funs acc e = funs.exp funs acc e
+and exp funs acc e =
+  let ed, acc = edesc_it funs acc e.e_desc in
+  { e with e_desc = ed }, acc
+
+
+and edesc_it funs acc ed =
+  try funs.edesc funs acc ed
+  with Fallback -> edesc funs acc ed
+and edesc funs acc ed = match ed with
+  | Elhs l ->
+     let l, acc = lhs_it funs acc l in
+        Elhs l, acc
+  | Econst se ->
+      let se, acc = static_exp_it funs.global_funs acc se in
+        Econst se, acc
+  | Eop (op, args) ->
+       let args, acc = mapfold (exp_it funs) acc args in
+         Eop (op, args), acc
+  | Estruct(tyn, f_e_list) ->
+      let aux acc (f,e) =
+        let e, acc = exp_it funs acc e in
+          (f,e), acc in
+      let f_e_list, acc = mapfold aux acc f_e_list in
+        Estruct(tyn, f_e_list), acc
+  | Earray args ->
+      let args, acc = mapfold (exp_it funs) acc args in
+        Earray args, acc
+
+
+and lhs_it funs acc l = funs.lhs funs acc l
+and lhs funs acc l =
+  let ld, acc = lhsdesc_it funs acc l.l_desc in
+  { l with l_desc = ld }, acc
+
+
+and lhsdesc_it funs acc ld =
+  try funs.lhsdesc funs acc ld
+  with Fallback -> lhsdesc funs acc ld
+and lhsdesc funs acc ld = match ld with
+  | Lvar x -> Lvar x, acc
+  | Lmem x -> Lmem x, acc
+  | Lfield(lhs, f) ->
+      let lhs, acc = lhs_it funs acc lhs in
+        Lfield(lhs, f), acc
+  | Larray(lhs, e) ->
+      let lhs, acc = lhs_it funs acc lhs in
+      let e, acc = exp_it funs acc e in
+        Larray(lhs, e), acc
+
+
+and act_it funs acc a =
+  try funs.act funs acc a
+  with Fallback -> act funs acc a
+and act funs acc a = match a with
+  | Aassgn(lhs, e) ->
+      let lhs, acc = lhs_it funs acc lhs in
+      let e, acc = exp_it funs acc e in
+        Aassgn(lhs, e), acc
+  | Acall(lhs_list, obj, n, args) ->
+      let lhs_list, acc = mapfold (lhs_it funs) acc lhs_list in
+      let args, acc = mapfold (exp_it funs) acc args in
+        Acall(lhs_list, obj, n, args), acc
+  | Acase(x, c_b_list) ->
+      let aux acc (c,b) =
+        let b, acc = block_it funs acc b in
+          (c,b), acc in
+      let c_b_list, acc = mapfold aux acc c_b_list in
+        Acase(x, c_b_list), acc
+  | Afor(x, idx1, idx2, b) ->
+      let idx1, acc = static_exp_it funs.global_funs acc idx1 in
+      let idx2, acc = static_exp_it funs.global_funs acc idx2 in
+      let b, acc = block_it funs acc b in
+        Afor(x, idx1, idx2, b), acc
+
+and block_it funs acc b = funs.block funs acc b
+and block funs acc b =
+  mapfold (act_it funs) acc b
+
+
+and var_dec_it funs acc vd = funs.var_dec funs acc vd
+and var_dec funs acc vd =
+  let v_type, acc = ty_it funs.global_funs acc vd.v_type in
+  { vd with v_type = v_type }, acc
+
+and var_decs_it funs acc vds = funs.var_decs funs acc vds
+and var_decs funs acc vds = mapfold (var_dec_it funs) acc vds
+
+
+and obj_dec_it funs acc od = funs.obj_dec funs acc od
+and obj_dec funs acc od =
+  let o_size, acc = optional_wacc
+    (static_exp_it funs.global_funs) acc od.o_size in
+  { od with o_size = o_size }, acc
+
+and obj_decs_it funs acc ods = funs.obj_decs funs acc ods
+and obj_decs funs acc ods = mapfold (obj_dec_it funs) acc ods
+
+
+and method_def_it funs acc md = funs.method_def funs acc md
+and method_def funs acc md =
+  let m_inputs, acc = var_decs_it funs acc md.m_inputs in
+  let m_outputs, acc = var_decs_it funs acc md.m_outputs in
+  let m_locals, acc = var_decs_it funs acc md.m_locals in
+  let m_body, acc = block_it funs acc md.m_body in
+  { md with
+      m_inputs = m_inputs; m_outputs = m_outputs;
+      m_locals = m_locals; m_body = m_body }
+  , acc
+
+
+and class_def_it funs acc cd = funs.class_def funs acc cd
+and class_def funs acc cd =
+  let cd_mems, acc = var_decs_it funs acc cd.cd_mems in
+  let cd_objs, acc = obj_decs_it funs acc cd.cd_objs in
+  let cd_params, acc = mapfold (param_it funs.global_funs) acc cd.cd_params in
+  let cd_methods, acc = mapfold (method_def_it funs) acc cd.cd_methods in
+  { cd with
+      cd_mems = cd_mems; cd_objs = cd_objs;
+      cd_params = cd_params; cd_methods = cd_methods }
+  , acc
+
+
+and const_dec_it funs acc c = funs.const_dec funs acc c
+and const_dec funs acc c =
+  let ty, acc = ty_it funs.global_funs acc c.c_type in
+  let se, acc = static_exp_it funs.global_funs acc c.c_value in
+  { c with c_type = ty; c_value = se }, acc
+
+
+and type_dec_it funs acc t = funs.type_dec funs acc t
+and type_dec funs acc t =
+  let tdesc, acc = tdesc_it funs acc t.t_desc in
+    { t with t_desc = tdesc }, acc
+
+
+and tdesc_it funs acc td =
+  try funs.tdesc funs acc td
+  with Fallback -> tdesc funs acc td
+and tdesc funs acc td = match td with
+  | Type_struct s ->
+      let s, acc = structure_it funs.global_funs acc s in
+        Type_struct s, acc
+  | _ -> td, acc
+
+
+and program_it funs acc p = funs.program funs acc p
+and program funs acc p =
+  let td_list, acc = mapfold (type_dec_it funs) acc p.p_types in
+  let cd_list, acc = mapfold (const_dec_it funs) acc p.p_consts in
+  let nd_list, acc = mapfold (class_def_it funs) acc p.p_defs in
+  { p with p_types = td_list; p_consts = cd_list; p_defs = nd_list }, acc
+
+
+let defaults = {
+  lhs = lhs;
+  lhsdesc = lhsdesc;
+  exp = exp;
+  edesc = edesc;
+  act = act;
+  block = block;
+  var_dec = var_dec;
+  var_decs = var_decs;
+  obj_dec = obj_dec;
+  obj_decs = obj_decs;
+  method_def = method_def;
+  class_def = class_def;
+  const_dec = const_dec;
+  type_dec = type_dec;
+  tdesc = tdesc;
+  program = program;
+  global_funs = Global_mapfold.defaults }