patterns.ml

exception Error of string
open Ident

(* Syntactic algebra *)
(* Constraint: any node except Constr has fv<>[] ... *)
type d =
  | Constr of Types.descr
  | Cup of descr * descr
  | Cap of descr * descr
  | Times of node * node
  | Xml of node * node
  | Record of label * node
  | Capture of id
  | Constant of id * Types.const
and node = {
  id : int;
  mutable descr : descr option;
  accept : Types.node;
  fv : fv
} and descr = Types.descr * fv * d

let id x = x.id
let descr x = match x.descr with Some d -> d | None -> failwith "Patterns.descr"
let fv x = x.fv
let accept x = Types.internalize x.accept

let printed = ref []
let to_print = ref []
let rec print ppf (a,_,d) = 
(*  Format.fprintf ppf "[%a]" Types.Print.print_descr a; *)
  match d with
    | Constr t -> Types.Print.print_descr ppf t
    | Cup (p1,p2) -> Format.fprintf ppf "(%a | %a)" print p1 print p2
    | Cap (p1,p2) -> Format.fprintf ppf "(%a & %a)" print p1 print p2
    | Times (n1,n2) -> 
	Format.fprintf ppf "(P%i,P%i)" n1.id n2.id;
	to_print := n1 :: n2 :: !to_print
    | Xml (n1,n2) -> 
	Format.fprintf ppf "XML(P%i,P%i)" n1.id n2.id;
	to_print := n1 :: n2 :: !to_print
    | Record (l,n) -> 
	Format.fprintf ppf "{ %s =  P%i }" (LabelPool.value l) n.id;
	to_print := n :: !to_print
    | Capture x ->
	Format.fprintf ppf "%s" (Id.value x)
    | Constant (x,c) ->
	Format.fprintf ppf "(%s := %a)" (Id.value x) 
	  Types.Print.print_const c

let dump_print ppf =
  while !to_print <> [] do
    let p = List.hd !to_print in
    to_print := List.tl !to_print;
    if not (List.mem p.id !printed) then
      ( printed := p.id :: !printed;
	Format.fprintf ppf "P%i:=%a\n" p.id print (descr p)
      )
  done

let print ppf d =
  Format.fprintf ppf "%a@\n" print d;
  dump_print ppf


let counter = State.ref "Patterns.counter" 0

let make fv =
  incr counter;
  { id = !counter; descr = None; accept = Types.make (); fv = fv }

let define x ((accept,fv,_) as d) =
  assert (x.fv = fv);
  Types.define x.accept accept;
  x.descr <- Some d

let constr x = (x,IdSet.empty,Constr x)
let cup ((acc1,fv1,_) as x1) ((acc2,fv2,_) as x2) = 
  if not (IdSet.equal fv1 fv2) then (
    let x = match IdSet.pick (IdSet.diff fv1 fv2) with
      | Some x -> x
      | None -> match IdSet.pick (IdSet.diff fv2 fv1) with Some x -> x 
	  | None -> assert false
    in
    raise 
      (Error 
	 ("The capture variable " ^ (Id.value x) ^ 
	  " should appear on both side of this | pattern"))
  );
  (Types.cup acc1 acc2, IdSet.cup fv1 fv2, Cup (x1,x2))
let cap ((acc1,fv1,_) as x1) ((acc2,fv2,_) as x2) = 
  if not (IdSet.disjoint fv1 fv2) then (
    match IdSet.pick (IdSet.cap fv1 fv2) with
      | Some x -> 
	  raise 
	  (Error 
	     ("The capture variable " ^ (Id.value x) ^ 
	      " cannot appear on both side of this & pattern"))
      | None -> assert false
  );
  (Types.cap acc1 acc2, IdSet.cup fv1 fv2, Cap (x1,x2))
let times x y =
  (Types.times x.accept y.accept, IdSet.cup x.fv y.fv, Times (x,y))
let xml x y =
  (Types.xml x.accept y.accept, IdSet.cup x.fv y.fv, Xml (x,y))
let record l x = 
  (Types.record l x.accept, x.fv, Record (l,x))
let capture x = (Types.any, IdSet.singleton x, Capture x)
let constant x c = (Types.any, IdSet.singleton x, Constant (x,c))




(* Static semantics *)

let cup_res v1 v2 = Types.Positive.cup [v1;v2]
let empty_res fv = IdMap.constant (Types.Positive.ty Types.empty) fv
let times_res v1 v2 = Types.Positive.times v1 v2

(* Try with a hash-table *)
module MemoFilter = Map.Make 
  (struct 
     type t = Types.descr * node 
     let compare (t1,n1) (t2,n2) = 
       if n1.id < n2.id then -1 else if n1.id > n2.id then 1 else
       Types.compare_descr t1 t2
   end)

let memo_filter = ref MemoFilter.empty

let rec filter_descr t (_,fv,d) : Types.Positive.v id_map =
(* TODO: avoid is_empty t when t is not changing (Cap) *)
  if Types.is_empty t 
  then empty_res fv
  else
    match d with
      | Constr _ -> IdMap.empty
      | Cup ((a,_,_) as d1,d2) ->
	  IdMap.merge cup_res
	    (filter_descr (Types.cap t a) d1)
	    (filter_descr (Types.diff t a) d2)
      | Cap (d1,d2) ->
	  IdMap.merge cup_res (filter_descr t d1) (filter_descr t d2)
      | Times (p1,p2) -> filter_prod fv p1 p2 t
      | Xml (p1,p2) -> filter_prod ~kind:`XML fv p1 p2 t
      | Record (l,p) ->
	  filter_node (Types.Record.project t l) p
      | Capture c ->
	  IdMap.singleton c (Types.Positive.ty t)
      | Constant (c, cst) ->
	  IdMap.singleton c (Types.Positive.ty (Types.constant cst))

and filter_prod ?kind fv p1 p2 t =
  List.fold_left 
    (fun accu (d1,d2) ->
       let term = 
	 IdMap.merge times_res (filter_node d1 p1) (filter_node d2 p2)
       in
       IdMap.merge cup_res accu term
    )
    (empty_res fv)
    (Types.Product.normal ?kind t)


and filter_node t p : Types.Positive.v id_map =
  try MemoFilter.find (t,p) !memo_filter
  with Not_found ->
    let (_,fv,_) as d = descr p in
    let res = IdMap.map_from_slist (fun _ -> Types.Positive.forward ()) fv in
    memo_filter := MemoFilter.add (t,p) res !memo_filter;
    let r = filter_descr t (descr p) in
    IdMap.collide Types.Positive.define res r;
    r

let filter t p =
  let r = filter_node t p in
  memo_filter :=  MemoFilter.empty;
  IdMap.get (IdMap.map Types.Positive.solve r)


(* Normal forms for patterns and compilation *)

let min (a:int) (b:int) = if a < b then a else b

module Normal : sig 
  type source = 
    | SCatch | SConst of Types.const 
    | SLeft | SRight | SRecompose 
  type result = source id_map

  module NodeSet : SortedList.S with type 'a elem = node
  type nnf = unit NodeSet.t * Types.descr

  module NLineBasic : SortedList.S with type 'a elem = result * Types.descr
  module NLineProd : SortedList.S with type 'a elem = result * nnf * nnf

  type record =
    | RecNolabel of result option * result option
    | RecLabel of label * unit NLineProd.t
  type t = {
    nfv    : fv;
    ncatchv: fv;
    na     : Types.descr;
    nbasic : unit NLineBasic.t;
    nprod  : unit NLineProd.t;
    nxml   : unit NLineProd.t;
    nrecord: record;
  }

  val dummy: t
  val compare_nf: t -> t -> int

  val any_basic: Types.descr
  val first_label: descr -> label
  val normal: label option -> Types.descr -> node list -> t
end = 
struct
  let any_basic = 
    Types.Record.or_absent
      (Types.neg (List.fold_left Types.cup Types.empty
		    [Types.Product.any_xml;
		     Types.Product.any;
		     Types.Record.any]))


  type source = 
    | SCatch | SConst of Types.const 
    | SLeft | SRight | SRecompose 
  type result = source id_map

  let compare_source s1 s2 =
    if s1 == s2 then 0 
    else match (s1,s2) with
      | SCatch, _ -> -1 | _, SCatch -> 1
      | SLeft, _ -> -1 | _, SLeft -> 1
      | SRight, _ -> -1 | _, SRight -> 1
      | SRecompose, _ -> -1 | _, SRecompose -> 1
      | SConst c1, SConst c2 -> Types.compare_const c1 c2

  let hash_source = function
    | SCatch -> 1
    | SLeft -> 2
    | SRight -> 3
    | SRecompose -> 4
    | SConst c -> Types.hash_const c
    
  let compare_result r1 r2 =
    IdMap.compare compare_source r1 r2

  let hash_result r =
    IdMap.hash hash_source r


  module NodeSet = 
    SortedList.Make(
      struct
	type 'a t = node
	let compare n1 n2 = n1.id - n2.id
	let equal n1 n2 = n1.id == n2.id
	let hash n = n.id
      end
    )

  type nnf = unit NodeSet.t * Types.descr (* pl,t;   t <= \accept{pl} *)

(*
  let rec compare_nodesl l1 l2 =
    if l1 == l2 then 0 
    else match (l1,l2) with
      | p1::l1, p2::l2 ->
	  if p1.id < p2.id then -1
	  else if p1.id > p2.id then 1
	  else compare_nodesl l1 l2
      | [], _ -> -1
      | _ -> 1
*)

  let compare_nnf (l1,t1) (l2,t2) =
    let c = NodeSet.compare l1 l2 in if c <> 0 then c
    else Types.compare_descr t1 t2

  let hash_nnf (l,t) =
    (NodeSet.hash l) + 17 * (Types.hash_descr t)

  module NLineBasic = 
    SortedList.Make(
      struct
	type 'a t = result * Types.descr
	let compare (r1,t1) (r2,t2) =
	  let c = compare_result r1 r2 in if c <> 0 then c
	  else Types.compare_descr t1 t2
	let equal x y = compare x y = 0
	let hash (r,t) = hash_result r + 17 * Types.hash_descr t
      end
    )

  module NLineProd = 
    SortedList.Make(
      struct
	type 'a t = result * nnf * nnf
	let compare (r1,x1,y1) (r2,x2,y2) =
	  let c = compare_result r1 r2 in if c <> 0 then c
	  else let c = compare_nnf x1 x2 in if c <> 0 then c
	  else compare_nnf y1 y2
	let equal x y = compare x y = 0
	let hash (r,x,y) =
	  hash_result r + 17 * (hash_nnf x) + 267 * (hash_nnf y)
      end
    )

  type record =
    | RecNolabel of result option * result option
    | RecLabel of label * unit NLineProd.t
  type t = {
    nfv    : fv;
    ncatchv: fv;
    na     : Types.descr;
    nbasic : unit NLineBasic.t;
    nprod  : unit NLineProd.t;
    nxml   : unit NLineProd.t;
    nrecord: record
  }

  let compare_nf t1 t2 =
    if t1 == t2 then 0
    else
      (* TODO: reorder; remove comparison of nfv ? *)
      let c = IdSet.compare t1.nfv t2.nfv in if c <> 0 then c 
      else let c = IdSet.compare t1.ncatchv t2.ncatchv in if c <> 0 then c
      else let c = Types.compare_descr t1.na t2.na in if c <> 0 then c
      else let c = NLineBasic.compare t1.nbasic t2.nbasic in if c <> 0 then c
      else let c = NLineProd.compare t1.nprod t2.nprod in if c <> 0 then c
      else let c = NLineProd.compare t1.nxml t2.nxml in if c <> 0 then c
      else match t1.nrecord, t2.nrecord with
	| RecNolabel (s1,n1), RecNolabel (s2,n2) ->
	    let c = match (s1,s2) with
	      | None,None -> 0
	      | Some r1, Some r2 -> compare_result r1 r2
	      | None, _ -> -1
	      | _, None -> 1 in
	    if c <> 0 then c 
	    else (match (n1,n2) with
	      | None,None -> 0
	      | Some r1, Some r2 -> compare_result r1 r2
	      | None, _ -> -1
	      | _, None -> 1)
	| RecNolabel (_,_), _ -> -1
	| _, RecNolabel (_,_) -> 1
	| RecLabel (l1,p1), RecLabel (l2,p2) ->
	    let c = LabelPool.compare l1 l2 in if c <> 0 then c
	    else NLineProd.compare p1 p2

  let fus = IdMap.union_disj

  let nempty lab = 
    { nfv = IdSet.empty; ncatchv = IdSet.empty; 
      na = Types.empty;
      nbasic = NLineBasic.empty; 
      nprod = NLineProd.empty; 
      nxml = NLineProd.empty;
      nrecord = (match lab with 
		   | Some l -> RecLabel (l,NLineProd.empty)
		   | None -> RecNolabel (None,None))
    }
  let dummy = nempty None


  let ncup nf1 nf2 = 
    (* assert (Types.is_empty (Types.cap nf1.na nf2.na)); *)
    (* assert (nf1.nfv = nf2.nfv); *)
    { nfv = nf1.nfv;
      ncatchv = IdSet.cap nf1.ncatchv nf2.ncatchv;
      na      = Types.cup nf1.na nf2.na;
      nbasic  = NLineBasic.cup nf1.nbasic nf2.nbasic;
      nprod   = NLineProd.cup nf1.nprod nf2.nprod;
      nxml    = NLineProd.cup nf1.nxml nf2.nxml;
      nrecord = (match (nf1.nrecord,nf2.nrecord) with
		   | RecLabel (l1,r1), RecLabel (l2,r2) -> 
		       assert (l1 = l2); RecLabel (l1, NLineProd.cup r1 r2)
		   | RecNolabel (x1,y1), RecNolabel (x2,y2) -> 
		       RecNolabel((if x1 = None then x2 else x1),
				(if y1 = None then y2 else y1))
		   | _ -> assert false)
    }

  let double_fold f l1 l2 =
    List.fold_left 
      (fun accu x1 -> List.fold_left (fun accu x2 -> f accu x1 x2) accu l2)
      [] l1

  let double_fold_prod f l1 l2 =
    double_fold f (NLineProd.get l1) (NLineProd.get l2)
	 
  let ncap nf1 nf2 =
    let prod accu (res1,(pl1,t1),(ql1,s1)) (res2,(pl2,t2),(ql2,s2)) =
      let t = Types.cap t1 t2 in
      if Types.is_empty t then accu else
	let s = Types.cap s1 s2  in
	if Types.is_empty s then accu else
	  (fus res1 res2, (NodeSet.cup pl1 pl2,t),(NodeSet.cup ql1 ql2,s)) 
	  :: accu
    in
    let basic accu (res1,t1) (res2,t2) =
      let t = Types.cap t1 t2 in
      if Types.is_empty t then accu else
	(fus res1 res2, t) :: accu
    in
    let record r1 r2 = match r1,r2 with
      | RecLabel (l1,r1), RecLabel (l2,r2) ->
	  assert (l1 = l2);
	  RecLabel(l1, NLineProd.from_list (double_fold_prod prod r1 r2))
      | RecNolabel (x1,y1), RecNolabel (x2,y2) ->
	  let x = match x1,x2 with 
	    | Some res1, Some res2 -> Some (fus res1 res2) 
	    | _ -> None
	  and y = match y1,y2 with
	    | Some res1, Some res2 -> Some (fus res1 res2)
	    | _ -> None in
	  RecNolabel (x,y)
      | _ -> assert false
    in
    { nfv = IdSet.cup nf1.nfv nf2.nfv;
      ncatchv = IdSet.cup nf1.ncatchv nf2.ncatchv;
      na = Types.cap nf1.na nf2.na;
      nbasic = NLineBasic.from_list (double_fold basic 
				       (NLineBasic.get nf1.nbasic) 
				       (NLineBasic.get nf2.nbasic));
      nprod = NLineProd.from_list (double_fold_prod prod nf1.nprod nf2.nprod);
      nxml = NLineProd.from_list (double_fold_prod prod nf1.nxml nf2.nxml);
      nrecord = record nf1.nrecord nf2.nrecord;
    }

  let nnode p = NodeSet.singleton p, Types.descr p.accept
  let nc t = NodeSet.empty, t
  let ncany = nc Types.any

  let empty_res = IdMap.empty

  let ntimes lab acc p q = 
    let src_p = IdMap.constant SLeft p.fv
    and src_q = IdMap.constant SRight q.fv in
    let src = IdMap.merge_elem SRecompose src_p src_q in 
    { nempty lab with 
	nfv = IdSet.cup p.fv q.fv; 
	na = acc;
	nprod = NLineProd.singleton (src, nnode p, nnode q);
    }

  let nxml lab acc p q = 
    let src_p = IdMap.constant SLeft p.fv
    and src_q = IdMap.constant SRight q.fv in
    let src = IdMap.merge_elem SRecompose src_p src_q in 
    { nempty lab with 
	nfv = IdSet.cup p.fv q.fv; 
	na = acc;
	nxml =  NLineProd.singleton (src, nnode p, nnode q);
    }
    
  let nrecord lab acc l p =
    match lab with
      | None -> assert false
      | Some label ->
(*	  Printf.eprintf "[ l = %s; label = %s ]\n" 
	    (LabelPool.value l)
	    (LabelPool.value label); *)
	  assert (label <= l);
	  if l == label then
	    let src = IdMap.constant SLeft p.fv in
	    { nempty lab with
		nfv = p.fv;
		na = acc;
		nrecord = RecLabel(label, 
				 NLineProd.singleton (src,nnode p, ncany))}
	  else
	    let src = IdMap.constant SRight p.fv in
	    let p' = make p.fv in  (* optimize this ... *)
	      (* cache the results to avoid looping ... *)
	    define p' (record l p);
	    { nempty lab with
		nfv = p.fv;
		na = acc;
		nrecord = 
		      RecLabel(label,
		        NLineProd.singleton(src,nc Types.Record.any_or_absent, 
 			 nnode p') )}
	  

  let nconstr lab t =
    let aux l = NLineProd.from_list
		(List.map (fun (t1,t2) -> empty_res, nc t1,nc t2) l) in
    let record = 
      match lab with
	| None ->
	    let (x,y) = Types.Record.empty_cases t in
	    RecNolabel ((if x then Some empty_res else None), 
		      (if y then Some empty_res else None))
	| Some l ->
	    RecLabel (l,aux (Types.Record.split_normal t l))
    in	      
    { nempty lab with
	na = t;
	nbasic = NLineBasic.singleton (empty_res, Types.cap t any_basic);
	nprod = aux (Types.Product.normal t);
	nxml  = aux (Types.Product.normal ~kind:`XML t);
	nrecord = record
    }

  let nconstant lab x c = 
    let l = IdMap.singleton x (SConst c) in
    { nfv = IdSet.singleton x;
      ncatchv = IdSet.empty;
      na = Types.any;
      nbasic = NLineBasic.singleton (l,any_basic); 
      nprod  = NLineProd.singleton (l,ncany,ncany);
      nxml   = NLineProd.singleton (l,ncany,ncany);
      nrecord = match lab with
	| None -> RecNolabel (Some l, Some l)
	| Some lab -> 
	    RecLabel (lab, NLineProd.singleton 
			(l,nc Types.Record.any_or_absent,
				 ncany))
    }

  let ncapture lab x = 
    let l = IdMap.singleton x SCatch in
    { nfv = IdSet.singleton x;
      ncatchv = IdSet.singleton x;
      na = Types.any;
      nbasic = NLineBasic.singleton (l,any_basic); 
      nprod  = NLineProd.singleton (l,ncany,ncany);
      nxml   = NLineProd.singleton (l,ncany,ncany);
      nrecord = match lab with
	| None -> RecNolabel (Some l, Some l)
	| Some lab -> 
	    RecLabel (lab, NLineProd.singleton 
			(l,nc Types.Record.any_or_absent,
			         ncany))
    }

  let rec nnormal lab (acc,fv,d) =
    if Types.is_empty acc 
    then nempty lab
    else match d with
      | Constr t -> nconstr lab t
      | Cap (p,q) -> ncap (nnormal lab p) (nnormal lab q)
      | Cup ((acc1,_,_) as p,q) -> 
	  ncup (nnormal lab p) (ncap (nnormal lab q) 
				  (nconstr lab (Types.neg acc1)))
      | Times (p,q) -> ntimes lab acc p q
      | Xml (p,q) -> nxml lab acc p q
      | Capture x -> ncapture lab x
      | Constant (x,c) -> nconstant lab x c
      | Record (l,p) -> nrecord lab acc l p

(*TODO: when an operand of Cap has its first_label > lab,
  directly shift it*)

  let rec first_label (acc,fv,d) =
    if Types.is_empty acc 
    then LabelPool.dummy_max
    else match d with
      | Constr t -> Types.Record.first_label t
      | Cap (p,q) -> min (first_label p) (first_label q)
      | Cup ((acc1,_,_) as p,q) -> min (first_label p) (first_label q)
	    (* should "first_label_type acc1" ? *)
      | Record (l,p) -> l
      | _ -> LabelPool.dummy_max

   
  let remove_catchv n =
    let ncv = n.ncatchv in
    let nlinesbasic l = 
      NLineBasic.map (fun (res,x) -> (IdMap.diff res ncv,x)) l in
    let nlinesprod l  = 
      NLineProd.map (fun (res,x,y) -> (IdMap.diff res ncv,x,y)) l in
    { nfv     = IdSet.diff n.nfv ncv;
      ncatchv = n.ncatchv;
      na      = n.na;
      nbasic  = nlinesbasic n.nbasic;
      nprod   = nlinesprod n.nprod;
      nxml    = nlinesprod n.nxml;
      nrecord = (match n.nrecord with
		   | RecNolabel (x,y) ->
		       let x = match x with 
			 | Some res -> Some (IdMap.diff res ncv) 
			 | None -> None in
		       let y = match y with 
			 | Some res -> Some (IdMap.diff res ncv) 
			 | None -> None in
		       RecNolabel (x,y)
		   | RecLabel (lab,l) -> RecLabel (lab, nlinesprod l))
    }

  let normal l t pl =
    remove_catchv
      (List.fold_left 
	 (fun a p -> ncap a (nnormal l (descr p))) 
	 (nconstr l t) 
	 pl)
end


module Compile = 
struct
  type actions =
    | AIgnore of result
    | AKind of actions_kind
  and actions_kind = {
    basic: (Types.descr * result) list;
    atoms: result Atoms.map;
    chars: result Chars.map;
    prod: result dispatch dispatch;
    xml: result dispatch dispatch;
    record: record option;
  }
  and record = 
    | RecLabel of label * result dispatch dispatch
    | RecNolabel of result option * result option
      
  and 'a dispatch =
    | Dispatch of dispatcher * 'a array
    | TailCall of dispatcher
    | Ignore of 'a
    | Impossible

  and result = int * source array
  and source = 
    | Catch | Const of Types.const 
    | Left of int | Right of int | Recompose of int * int
      
  and return_code = 
      Types.descr * int *   (* accepted type, arity *)
      (int * int id_map) list

  and interface =
    [ `Result of int
    | `Switch of interface * interface
    | `None ]

  and dispatcher = {
    id : int;
    t  : Types.descr;
    pl : Normal.t array;
    label : label option;
    interface : interface;
    codes : return_code array;
    mutable actions : actions option;
    mutable printed : bool
  }

  let array_for_all f a =
    let rec aux f a i =
      if i = Array.length a then true
      else f a.(i) && (aux f a (succ i))
    in
    aux f a 0

  let array_for_all_i f a =
    let rec aux f a i =
      if i = Array.length a then true
      else f i a.(i) && (aux f a (succ i))
    in
    aux f a 0

  let combine_kind basic prod xml record =
    try (
      let rs = [] in
      let rs = match basic with
	| [_,r] -> r :: rs
	| [] -> rs
	| _ -> raise Exit in
      let rs = match prod with
	| Impossible -> rs
	| Ignore (Ignore r) -> r :: rs
	| _ -> raise Exit in
      let rs = match xml with
	| Impossible -> rs
	| Ignore (Ignore r) -> r :: rs
	| _ -> raise Exit in
      let rs = match record with
	| None -> rs
	| Some (RecLabel (_,Ignore (Ignore r))) -> r :: rs
	| Some (RecNolabel (Some r1, Some r2)) -> r1 :: r2 :: rs
	| _ -> raise Exit in
      match rs with
	| ((_, ret) as r) :: rs when 
	    List.for_all ( (=) r ) rs 
	    && array_for_all 
	      (function Catch | Const _ -> true | _ -> false) ret
	    -> AIgnore r
	| _ -> raise Exit
    )
    with Exit -> 
      AKind 
      { basic = basic;
	atoms = 
	   Atoms.mk_map (List.map (fun (t,r) -> Types.Atom.get t, r) basic);
	chars = 
	   Chars.mk_map (List.map (fun (t,r) -> Types.Char.get t, r) basic);
	prod = prod; 
	xml = xml; 
	record = record }
      
  let combine (disp,act) =
    if Array.length act = 0 then Impossible
    else
      if (array_for_all (fun (_,ar,_) -> ar = 0) disp.codes) 
	 && (array_for_all ( (=) act.(0) ) act) then
	   Ignore act.(0)
      else
	Dispatch (disp, act)


  let detect_right_tail_call = function
    | Dispatch (disp,branches) 
	when
	  array_for_all_i
	    (fun i (code,ret) ->
	       (i = code) && 
	       (array_for_all_i 
		  (fun pos -> 
		     function Right j when pos = j -> true | _ -> false)
		  ret
	       )
	    ) branches
	  -> TailCall disp
    | x -> x

  let detect_left_tail_call = function
    | Dispatch (disp,branches)
	when
	  array_for_all_i
	    (fun i -> 
	       function 
		 | Ignore (code,ret) ->
		     (i = code) &&
		     (array_for_all_i 
			(fun pos -> 
			   function Left j when pos = j -> true | _ -> false)
			ret
	       )
		 | _ -> false
	    ) branches
 	  ->
	 TailCall disp
    | x -> x
   
  let cur_id = State.ref "Patterns.cur_id" 0
		 (* TODO: save dispatchers ? *)
		 
  module NfMap = Map.Make(
    struct 
      type t = Normal.t
      let compare = Normal.compare_nf
    end)

  module DispMap = Map.Make(
    struct
      type t = Types.descr * Normal.t array

      let rec compare_rec a1 a2 i =
	if i < 0 then 0 
	else
	  let c = Normal.compare_nf a1.(i) a2.(i) in
	  if c <> 0 then c else compare_rec a1 a2 (i - 1)
	  
      let compare (t1,a1) (t2,a2) =
	let c = Types.compare_descr t1 t2 in if c <> 0 then c 
	else let l1 = Array.length a1 and l2 = Array.length a2 in
	if l1 < l2 then -1 else if l1 > l2 then 1
	else compare_rec a1 a2 (l1 - 1)
    end
  )

    (* Try with a hash-table ! *)
    
  let dispatchers = ref DispMap.empty
		      
  let dispatcher t pl lab : dispatcher =
    try DispMap.find (t,pl) !dispatchers
    with Not_found ->
      let nb = ref 0 in
      let codes = ref [] in
      let rec aux t arity i accu = 
	if Types.is_empty t then `None
	else
	  if i = Array.length pl 
	  then (incr nb; codes := (t,arity,accu)::!codes; `Result (!nb - 1))
	  else
	    let p = pl.(i) in
	    let tp = p.Normal.na in
	    let v = p.Normal.nfv in
(*	    let tp = Types.normalize tp in *)
	    let accu' = (i,IdMap.num arity v) :: accu in
	    `Switch 
	      (
	       aux (Types.cap t tp) (arity + (IdSet.length v)) (i+1) accu',
	       aux (Types.diff t tp) arity (i+1) accu
	      )
      in
      let iface = aux t 0 0 [] in
      let res = { id = !cur_id; 
		  t = t;
		  label = lab;
		  pl = pl;
		  interface = iface;
		  codes = Array.of_list (List.rev !codes);
		  actions = None; printed = false } in
      incr cur_id;
      dispatchers := DispMap.add (t,pl) res !dispatchers;
      res
    
  let find_code d a =
    let rec aux i = function
      | `Result code -> code
      | `None -> assert false
      | `Switch (yes,_) when a.(i) <> None -> aux (i + 1) yes
      | `Switch (_,no) -> aux (i + 1) no
    in
    aux 0 d.interface

  let create_result pl =
    let aux x accu = match x with Some b -> b @ accu | None -> accu in
    Array.of_list (Array.fold_right aux pl [])

  let return disp pl f =
    let aux = function [x] -> Some (f x) | [] -> None | _ -> assert false in
    let final = Array.map aux pl in
    (find_code disp final, create_result final)
    
  let conv_source_basic s = match s with
    | Normal.SCatch -> Catch
    | Normal.SConst c -> Const c
    | _ -> assert false

  let assoc v l =
    try IdMap.assoc v l with Not_found -> -1

  let conv_source_prod left right v s = match s with
    | Normal.SCatch -> Catch
    | Normal.SConst c -> Const c
    | Normal.SLeft -> Left (assoc v left)
    | Normal.SRight -> Right (assoc v right)
    | Normal.SRecompose -> Recompose (assoc v left, assoc v right)

  let dispatch_basic disp : (Types.descr * result) list =
(* TODO: try other algo, using disp.codes .... *)
    let pl = Array.map (fun p -> p.Normal.nbasic) disp.pl in
    let tests =
      let accu = ref [] in
      let aux i (res,x) = accu := (x, [i,res]) :: !accu in
      Array.iteri (fun i -> Normal.NLineBasic.iter (aux i)) pl;
      Types.DescrSList.Map.get (Types.DescrSList.Map.from_list (@) !accu) in

    let t = Types.cap Normal.any_basic disp.t in
    let accu = ref [] in
    let rec aux (success : (int * Normal.result) list) t l = 
      if Types.non_empty t 
      then match l with
	| [] ->
	    let selected = Array.create (Array.length pl) [] in
	    let add (i,res) = selected.(i) <- res :: selected.(i) in
	    List.iter add success;
	    
	    let aux_final res = IdMap.map_to_list conv_source_basic res in
	    accu := (t, return disp selected aux_final) :: !accu
	| (ty,i) :: rem -> 
	    aux (i @ success) (Types.cap t ty) rem; 
	    aux success (Types.diff t ty) rem
    in
    aux [] t tests;
    !accu


  let get_tests pl f t d post =
    let accu = ref [] in
    let aux i x = 
      let (pl,ty), info = f x in
      let pl = Normal.NodeSet.get pl in
      accu := (ty,pl,i,info) :: !accu in
    Array.iteri (fun i -> List.iter (aux i)) pl;

    let lab =
      List.fold_left 
	(fun l (ty,pl,_,_) ->
	   List.fold_left
	     (fun l p -> min l (Normal.first_label (descr p)))
	     (min l (Types.Record.first_label ty))
	     pl
	) LabelPool.dummy_max !accu in
    let lab = if lab= LabelPool.dummy_max then None else Some lab in


    let pats = ref NfMap.empty in
    let nb_p = ref 0 in
    List.iter
      (fun (ty,pl,i,info) -> 
	 let p = Normal.normal lab ty pl in
	 let x = (i, p.Normal.ncatchv, info) in
	 try 
	   let s = NfMap.find p !pats in
	   s := x :: !s
	 with Not_found ->
	   pats := NfMap.add p (ref [x]) !pats;
	   incr nb_p
      ) !accu;
    let infos = Array.make !nb_p [] in
    let ps = Array.make !nb_p Normal.dummy in
    let count = ref 0 in
    NfMap.iter (fun p l ->
		  let i = !count in
		  infos.(i) <- !l;
		  ps.(i) <- p;
		  count := succ i) !pats;
    assert( !nb_p = !count );
    let disp = dispatcher t ps lab in

    let result (t,_,m) =
      let selected = Array.create (Array.length pl) [] in
      let add r (i, ncv, inf) = selected.(i) <- (r,ncv,inf) :: selected.(i) in
      List.iter (fun (j,r) -> List.iter (add r) infos.(j)) m;
      d t selected
    in
    let res = Array.map result disp.codes in
    post (disp,res)


  let make_branches t brs =
    let (_,brs) = 
      List.fold_left
	(fun (t,brs) (p,e) ->
	   let p' = (Normal.NodeSet.singleton p,t) in
	   let t' = Types.diff t (Types.descr (accept p)) in
	   (t', (p',e) :: brs)
	) (t,[]) brs in
	
    let pl = Array.map (fun x -> [x]) (Array.of_list brs) in
    get_tests 
      pl 
      (fun x -> x)
      t
      (fun _ pl ->
	 let r = ref None in
	 let aux = function