diff --git a/compiler/heptagon/analysis/typing.ml b/compiler/heptagon/analysis/typing.ml
index 5ee9e6c..0c35358 100644
--- a/compiler/heptagon/analysis/typing.ml
+++ b/compiler/heptagon/analysis/typing.ml
@@ -47,6 +47,7 @@ type error =
   | Eno_such_field of ty * longname
   | Eempty_record
   | Eempty_array
+  | Efoldi_bad_args of ty
 
 exception Unify
 exception TypingError of error
@@ -163,6 +164,12 @@ let message loc kind =
         Printf.eprintf
           "%aThe array is empty.\n"
           output_location loc
+    | Efoldi_bad_args  ty ->
+        Printf.eprintf
+          "%aThe function given to foldi should expect an integer \
+               as the last but one argument (found: %a).\n"
+          output_location loc
+          Hept_printer.ptype ty
   end;
   raise Error
 
@@ -791,6 +798,22 @@ and typing_iterator statefull const_env h
         with TypingError(kind) -> message (List.hd e_list).e_loc kind );
       (List.hd result_ty_list), typed_e_list
 
+  | Ifoldi ->
+      let args_ty_list, acc_ty = split_last args_ty_list in
+      let args_ty_list, idx_ty = split_last args_ty_list in
+        (* Last but one arg of the function should be integer *)
+        ( try unify idx_ty (Tid Initial.pint)
+          with TypingError _ -> raise (TypingError (Efoldi_bad_args idx_ty)));
+        let args_ty_list =
+        incomplete_map (fun ty -> Tarray (ty, n)) (args_ty_list@[acc_ty]) in
+      let typed_e_list =
+        typing_args statefull const_env h args_ty_list e_list in
+      (*check accumulator type matches in input and output*)
+      if List.length result_ty_list > 1 then error Etoo_many_outputs;
+      ( try unify (last_element args_ty_list) (List.hd result_ty_list)
+        with TypingError(kind) -> message (List.hd e_list).e_loc kind );
+      (List.hd result_ty_list), typed_e_list
+
     | Imapfold ->
       let args_ty_list =
         incomplete_map (fun ty -> Tarray (ty, n)) args_ty_list in
diff --git a/compiler/heptagon/hept_printer.ml b/compiler/heptagon/hept_printer.ml
index 1ebac7e..6c0c6f5 100644
--- a/compiler/heptagon/hept_printer.ml
+++ b/compiler/heptagon/hept_printer.ml
@@ -24,6 +24,7 @@ let iterator_to_string i =
   match i with
     | Imap -> "map"
     | Ifold -> "fold"
+    | Ifoldi -> "foldi"
     | Imapfold -> "mapfold"
 
 let print_iterator ff it =
diff --git a/compiler/heptagon/heptagon.ml b/compiler/heptagon/heptagon.ml
index eb2e79d..4b239ad 100644
--- a/compiler/heptagon/heptagon.ml
+++ b/compiler/heptagon/heptagon.ml
@@ -20,6 +20,7 @@ type state_name = name
 type iterator_type =
   | Imap
   | Ifold
+  | Ifoldi
   | Imapfold
 
 type exp = { e_desc : desc; e_ty : ty; e_loc : location }
diff --git a/compiler/heptagon/parsing/hept_lexer.mll b/compiler/heptagon/parsing/hept_lexer.mll
index 9f78891..8dac830 100644
--- a/compiler/heptagon/parsing/hept_lexer.mll
+++ b/compiler/heptagon/parsing/hept_lexer.mll
@@ -59,6 +59,7 @@ List.iter (fun (str,tok) -> Hashtbl.add keyword_table str tok) [
  "with", WITH;
  "map", MAP;
  "fold", FOLD;
+ "foldi", FOLDI;
  "mapfold", MAPFOLD;
  "quo", INFIX3("quo");
  "mod", INFIX3("mod");
@@ -115,7 +116,7 @@ let char_for_decimal_code lexbuf i =
 }
 
 
-let newline = '\n' | '\r' '\n' 
+let newline = '\n' | '\r' '\n'
 
 rule token = parse
   | newline         { new_line lexbuf; token lexbuf }
@@ -138,7 +139,7 @@ rule token = parse
   | "|"             {BAR}
   | "-"             {SUBTRACTIVE "-"}
   | "-."            {SUBTRACTIVE "-."}
-  | "^"             {POWER} 
+  | "^"             {POWER}
   | "["             {LBRACKET}
   | "]"             {RBRACKET}
   | "@"             {AROBASE}
@@ -151,9 +152,9 @@ rule token = parse
       { let s = Lexing.lexeme lexbuf in
           begin try
 	    Hashtbl.find keyword_table s
-          with 
+          with
 	      Not_found -> IDENT id
-	  end 
+	  end
       }
   | ['0'-'9']+
   | '0' ['x' 'X'] ['0'-'9' 'A'-'F' 'a'-'f']+
diff --git a/compiler/heptagon/parsing/hept_parser.mly b/compiler/heptagon/parsing/hept_parser.mly
index f67bca6..8a567df 100644
--- a/compiler/heptagon/parsing/hept_parser.mly
+++ b/compiler/heptagon/parsing/hept_parser.mly
@@ -45,7 +45,7 @@ open Hept_parsetree
 %token DOUBLE_DOT
 %token AROBASE
 %token DOUBLE_LESS DOUBLE_GREATER
-%token MAP FOLD MAPFOLD
+%token MAP FOLD FOLDI MAPFOLD
 %token <string> PREFIX
 %token <string> INFIX0
 %token <string> INFIX1
@@ -475,6 +475,7 @@ call_params:
 iterator:
   | MAP { Imap }
   | FOLD { Ifold }
+  | FOLDI { Ifoldi }
   | MAPFOLD { Imapfold }
 ;
 
diff --git a/compiler/heptagon/parsing/hept_parsetree.ml b/compiler/heptagon/parsing/hept_parsetree.ml
index 8d62aa4..eefafbf 100644
--- a/compiler/heptagon/parsing/hept_parsetree.ml
+++ b/compiler/heptagon/parsing/hept_parsetree.ml
@@ -16,6 +16,7 @@ open Types
 type iterator_type =
   | Imap
   | Ifold
+  | Ifoldi
   | Imapfold
 
 type ty =
diff --git a/compiler/heptagon/parsing/hept_scoping.ml b/compiler/heptagon/parsing/hept_scoping.ml
index e70efed..fa6e474 100644
--- a/compiler/heptagon/parsing/hept_scoping.ml
+++ b/compiler/heptagon/parsing/hept_scoping.ml
@@ -98,6 +98,7 @@ let build_id_list loc env l =
 let translate_iterator_type = function
   | Imap -> Heptagon.Imap
   | Ifold -> Heptagon.Ifold
+  | Ifoldi -> Heptagon.Ifoldi
   | Imapfold -> Heptagon.Imapfold
 
 let op_from_app loc app =
diff --git a/compiler/main/hept2mls.ml b/compiler/main/hept2mls.ml
index f9b5370..c0a4943 100644
--- a/compiler/main/hept2mls.ml
+++ b/compiler/main/hept2mls.ml
@@ -192,6 +192,7 @@ let translate_reset = function
 let translate_iterator_type = function
   | Heptagon.Imap -> Imap
   | Heptagon.Ifold -> Ifold
+  | Heptagon.Ifoldi -> Ifoldi
   | Heptagon.Imapfold -> Imapfold
 
 let rec translate_op env = function
diff --git a/compiler/main/mls2obc.ml b/compiler/main/mls2obc.ml
index 1329e0e..b8e61b6 100644
--- a/compiler/main/mls2obc.ml
+++ b/compiler/main/mls2obc.ml
@@ -391,6 +391,17 @@ and translate_iterator map call_context it name_list app loc n x c_list =
           si, j, [ Aassgn (acc_out, acc_in);
                    Afor (x, static_exp_of_int 0, n, b) ]
 
+    | Minils.Ifoldi ->
+        let (c_list, acc_in) = split_last c_list in
+        let c_list = array_of_input c_list in
+        let acc_out = last_element name_list in
+        let v, si, j, action = mk_node_call map call_context
+          app loc name_list (c_list @ [ mk_evar x; mk_exp (Elhs acc_out) ]) in
+        let v = translate_var_dec map v in
+        let b = mk_block ~locals:v action in
+          si, j, [ Aassgn (acc_out, acc_in);
+                   Afor (x, static_exp_of_int 0, n, b) ]
+
 let remove m d_list =
   List.filter (fun { Minils.v_ident = n } -> not (List.mem_assoc n m)) d_list
 
diff --git a/compiler/minils/minils.ml b/compiler/minils/minils.ml
index cd19a33..0fa6baa 100644
--- a/compiler/minils/minils.ml
+++ b/compiler/minils/minils.ml
@@ -24,6 +24,7 @@ let minils_format_version = "1"
 type iterator_type =
   | Imap
   | Ifold
+  | Ifoldi
   | Imapfold
 
 type type_dec = {
diff --git a/compiler/minils/mls_printer.ml b/compiler/minils/mls_printer.ml
index 065d042..ab569cb 100644
--- a/compiler/minils/mls_printer.ml
+++ b/compiler/minils/mls_printer.ml
@@ -21,6 +21,7 @@ let iterator_to_string i =
   match i with
     | Imap -> "map"
     | Ifold -> "fold"
+    | Ifoldi -> "foldi"
     | Imapfold -> "mapfold"
 
 let rec print_pat ff = function