CristalCaveGem » LustreC

(********************************************************************)

(*                                                                  *)

(*  The LustreC compiler toolset   /  The LustreC Development Team  *)

(*  Copyright 2012 -    --   ONERA - CNRS - INPT - LIFL             *)

(*                                                                  *)

(*  LustreC is free software, distributed WITHOUT ANY WARRANTY      *)

(*  under the terms of the GNU Lesser General Public License        *)

(*  version 2.1.                                                    *)

(*                                                                  *) 

(*  This file was originally from the Prelude compiler              *)

(*                                                                  *) 

(********************************************************************)

(** Clocks definitions and a few utility functions on clocks. *)

open Utils

open Format

(* Clock type sets, for subtyping. *)

type clock_set =

    CSet_all

  | CSet_pck of int*rat

(* Clock carriers basically correspond to the "c" in "x when c" *)

type carrier_desc =

  | Carry_const of ident

  | Carry_name

  | Carry_var

  | Carry_link of carrier_expr

(* Carriers are scoped, to detect clock extrusion. In other words, we

   check the scope of a clock carrier before generalizing it. *)

and carrier_expr =

    {mutable carrier_desc: carrier_desc;

     mutable carrier_scoped: bool;

     carrier_id: int}

type clock_expr =

    {mutable cdesc: clock_desc;

     mutable cscoped: bool;

     cid: int}

(* pck stands for periodic clock. Easier not to separate pck from other clocks *)

and clock_desc =

  | Carrow of clock_expr * clock_expr

  | Ctuple of clock_expr list

  | Con of clock_expr * carrier_expr * ident

  | Pck_up of clock_expr * int

  | Pck_down of clock_expr * int

  | Pck_phase of clock_expr * rat

  | Pck_const of int * rat

  | Cvar of clock_set (* Monomorphic clock variable *)

  | Cunivar of clock_set (* Polymorphic clock variable *)

  | Clink of clock_expr (* During unification, make links instead of substitutions *)

  | Ccarrying of carrier_expr * clock_expr

type error =

  | Clock_clash of clock_expr * clock_expr

  | Not_pck

  | Clock_set_mismatch of clock_expr * clock_set

  | Cannot_be_polymorphic of clock_expr

  | Invalid_imported_clock of clock_expr

  | Invalid_const of clock_expr

  | Factor_zero

  | Carrier_mismatch of carrier_expr * carrier_expr

  | Carrier_extrusion of clock_expr * carrier_expr

  | Clock_extrusion of clock_expr * clock_expr

exception Unify of clock_expr * clock_expr

exception Subsume of clock_expr * clock_set

exception Mismatch of carrier_expr * carrier_expr

exception Scope_carrier of carrier_expr

exception Scope_clock of clock_expr

exception Error of Location.t * error

let print_ckset fmt s =

  match s with

  | CSet_all -> ()

  | CSet_pck (k,q) ->

      let (a,b) = simplify_rat q in

      if k = 1 && a = 0 then

        fprintf fmt "<:P"

      else

        fprintf fmt "<:P_(%i,%a)" k print_rat (a,b)

let rec print_carrier fmt cr =

 (* (if cr.carrier_scoped then fprintf fmt "[%t]" else fprintf fmt "%t") (fun fmt -> *)

  match cr.carrier_desc with

  | Carry_const id -> fprintf fmt "%s" id

  | Carry_name ->

      fprintf fmt "_%s" (name_of_carrier cr.carrier_id)

  | Carry_var ->

    fprintf fmt "'%s" (name_of_carrier cr.carrier_id)

  | Carry_link cr' ->

    print_carrier fmt cr'

(* Simple pretty-printing, performs no simplifications. Linear

   complexity. For debug mainly. *)

let rec print_ck_long fmt ck =

  match ck.cdesc with

  | Carrow (ck1,ck2) ->

      fprintf fmt "%a -> %a" print_ck_long ck1 print_ck_long ck2

  | Ctuple cklist ->

    fprintf fmt "(%a)"

      (fprintf_list ~sep:" * " print_ck_long) cklist

  | Con (ck,c,l) ->

    fprintf fmt "%a on %s(%a)" print_ck_long ck l print_carrier c

  | Pck_up (ck,k) ->

    fprintf fmt "%a*^%i" print_ck_long ck k

  | Pck_down (ck,k) ->

    fprintf fmt "%a/^%i" print_ck_long ck k

  | Pck_phase (ck,q) ->

    fprintf fmt "%a~>%a" print_ck_long ck print_rat (simplify_rat q)

  | Pck_const (n,p) ->

    fprintf fmt "(%i,%a)" n print_rat (simplify_rat p)

  | Cvar cset ->

    fprintf fmt "'_%i%a" ck.cid print_ckset cset

  | Cunivar cset ->

    fprintf fmt "'%i%a" ck.cid print_ckset cset

  | Clink ck' ->

    fprintf fmt "link %a" print_ck_long ck'

  | Ccarrying (cr,ck') ->

    fprintf fmt "(%a:%a)" print_carrier cr print_ck_long ck'

let new_id = ref (-1)

let new_ck desc scoped =

  incr new_id; {cdesc=desc; cid = !new_id; cscoped = scoped}

let new_var scoped =

  new_ck (Cvar CSet_all) scoped

let new_univar () =

  new_ck (Cunivar CSet_all) false

let new_carrier_id = ref (-1)

let new_carrier desc scoped =

  incr new_carrier_id; {carrier_desc = desc;

                        carrier_id = !new_carrier_id;

                        carrier_scoped = scoped}

let new_carrier_name () =

  new_carrier Carry_name true

let rec repr =

  function

      {cdesc=Clink ck'} ->

        repr ck'

    | ck -> ck

let rec carrier_repr =

  function {carrier_desc = Carry_link cr'} -> carrier_repr cr'

    | cr -> cr

(** Splits [ck] into the [lhs,rhs] of an arrow clock. Expects an arrow clock

    (ensured by language syntax) *)

let split_arrow ck =

  match (repr ck).cdesc with

  | Carrow (cin,cout) -> cin,cout

    (* Functions are not first order, I don't think the var case

       needs to be considered here *)

  | _ -> failwith "Internal error: not an arrow clock"

let get_carrier_name ck =

 match (repr ck).cdesc with

 | Ccarrying (cr, _) -> Some cr

 | _                 -> None

let rename_carrier_static rename cr =

  match (carrier_repr cr).carrier_desc with

  | Carry_const id -> { cr with carrier_desc = Carry_const (rename id) }

  | _              -> (Format.eprintf "internal error: Clocks.rename_carrier_static %a@." print_carrier cr; assert false)

let rec rename_static rename ck =

 match (repr ck).cdesc with

 | Ccarrying (cr, ck') -> { ck with cdesc = Ccarrying (rename_carrier_static rename cr, rename_static rename ck') }

 | Con (ck', cr, l)    -> { ck with cdesc = Con (rename_static rename ck', rename_carrier_static rename cr, l) }

 | _                   -> ck

let uncarrier ck =

 match ck.cdesc with

 | Ccarrying (_, ck') -> ck'

 | _                  -> ck

(* Removes all links in a clock. Only used for clocks

   simplification though. *)

let rec deep_repr ck =

  match ck.cdesc with

  | Carrow (ck1,ck2) ->

      new_ck (Carrow (deep_repr ck1, deep_repr ck2)) ck.cscoped

  | Ctuple cl ->

      new_ck (Ctuple (List.map deep_repr cl)) ck.cscoped

  | Con (ck', c, l) ->

      new_ck (Con (deep_repr ck', c, l)) ck.cscoped

  | Pck_up (ck',k) ->

      new_ck (Pck_up (deep_repr ck',k)) ck.cscoped

  | Pck_down (ck',k) ->

      new_ck (Pck_down (deep_repr ck',k)) ck.cscoped

  | Pck_phase (ck',q) ->

      new_ck (Pck_phase (deep_repr ck',q)) ck.cscoped

  | Pck_const (_,_) | Cvar _ | Cunivar _ -> ck

  | Clink ck' -> deep_repr ck'

  | Ccarrying (cr,ck') -> new_ck (Ccarrying (cr, deep_repr ck')) ck.cscoped

(** Splits ck into the [lhs,rhs] of an arrow clock. Expects an arrow clock

    (ensured by language syntax) *)

let split_arrow ck =

  match (repr ck).cdesc with

  | Carrow (cin,cout) -> cin,cout

  | _ -> failwith "Internal error: not an arrow clock"

(** Returns the clock corresponding to a clock list. *)

let clock_of_clock_list ckl =

  if (List.length ckl) > 1 then

    new_ck (Ctuple ckl) true

  else

    List.hd ckl

let clock_list_of_clock ck =

 match (repr ck).cdesc with

 | Ctuple cl -> cl

 | _         -> [ck]

let clock_on ck cr l =

 clock_of_clock_list (List.map (fun ck -> new_ck (Con (ck,cr,l)) true) (clock_list_of_clock ck))

let clock_current ck =

 clock_of_clock_list (List.map (fun ck -> match (repr ck).cdesc with Con(ck',_,_) -> ck' | _ -> assert false) (clock_list_of_clock ck))

let clock_of_impnode_clock ck =

  let ck = repr ck in

  match ck.cdesc with

  | Carrow _ | Clink _ | Cvar _ | Cunivar _ ->

      failwith "internal error clock_of_impnode_clock"

  | Ctuple cklist -> List.hd cklist

  | Con (_,_,_) | Pck_up (_,_) | Pck_down (_,_) | Pck_phase (_,_)

  | Pck_const (_,_) | Ccarrying (_,_) -> ck

(** [intersect set1 set2] returns the intersection of clock subsets

    [set1] and [set2]. *)

let intersect set1 set2 =

  match set1,set2 with

  | CSet_all,_ -> set2

  | _,CSet_all -> set1

  | CSet_pck (k,q), CSet_pck (k',q') ->

      let k'',q'' = lcm k k',max_rat q q' in

      CSet_pck (k'',q'')

(** [can_be_pck ck] returns true if [ck] "may be" a pclock (the uncertainty is

    due to clock variables) *)

let rec can_be_pck ck =

  match (repr ck).cdesc with

  | Pck_up (_,_) | Pck_down (_,_) | Pck_phase (_,_) | Pck_const (_,_)

  | Cvar _ | Cunivar _ ->

      true

  | Ccarrying (_,ck') -> can_be_pck ck

  | _ -> false

(** [is_concrete_pck ck] returns true if [ck] is a concrete [pck] (pck

    transformations applied to a pck constant) *)

let rec is_concrete_pck ck =

  match ck.cdesc with

  | Carrow (_,_) | Ctuple _ | Con (_,_,_)

  | Cvar _ | Cunivar _ -> false

  | Pck_up (ck',_) | Pck_down (ck',_) -> is_concrete_pck ck'

  | Pck_phase (ck',_) -> is_concrete_pck ck'

  | Pck_const (_,_) -> true

  | Clink ck' -> is_concrete_pck ck'

  | Ccarrying (_,ck') -> false

(** [is_polymorphic ck] returns true if [ck] is polymorphic. *)

let rec is_polymorphic ck =

  match ck.cdesc with

  | Cvar _ | Pck_const (_,_) -> false

  | Carrow (ck1,ck2) -> (is_polymorphic ck1) || (is_polymorphic ck2)

  | Ctuple ckl -> List.exists (fun c -> is_polymorphic c) ckl

  | Con (ck',_,_) -> is_polymorphic ck'

  | Pck_up (ck',_) | Pck_down (ck',_) -> is_polymorphic ck'

  | Pck_phase (ck',_) -> is_polymorphic ck'

  | Cunivar _ -> true

  | Clink ck' -> is_polymorphic ck'

  | Ccarrying (_,ck') -> is_polymorphic ck'

(** [constrained_vars_of_clock ck] returns the clock variables subject

    to sub-typing constraints appearing in clock [ck]. Removes duplicates *)

(* Used mainly for debug, non-linear complexity. *)

let rec constrained_vars_of_clock ck =

  let rec aux vars ck =

    match ck.cdesc with

    | Pck_const (_,_) ->

        vars

    | Cvar cset ->

        begin

          match cset with

          | CSet_all -> vars

          | _ ->

              list_union [ck] vars

        end

    | Carrow (ck1,ck2) ->

        let l = aux vars ck1 in

        aux l ck2

    | Ctuple ckl ->

        List.fold_left

          (fun acc ck' -> aux acc ck') 

          vars ckl

    | Con (ck',_,_) -> aux vars ck'

    | Pck_up (ck',_) | Pck_down (ck',_) -> aux vars ck'

    | Pck_phase (ck',_) -> aux vars ck'

    | Cunivar cset ->

        begin

          match cset with

          | CSet_all -> vars

          | _ -> list_union [ck] vars

        end

    | Clink ck' -> aux vars ck'

    | Ccarrying (_,ck') -> aux vars ck'

  in

  aux [] ck

(** [period ck] returns the period of [ck]. Expects a constant pclock

    expression belonging to the correct clock set. *)

let rec period ck =

  let rec aux ck =

    match ck.cdesc with

    | Carrow (_,_) | Ctuple _ | Con (_,_,_)

    | Cvar _ | Cunivar _ ->

        failwith "internal error: can only compute period of const pck"

    | Pck_up (ck',k) ->

        (aux ck')/.(float_of_int k)

    | Pck_down (ck',k) ->

        (float_of_int k)*.(aux ck')

    | Pck_phase (ck',_) ->

        aux ck'

    | Pck_const (n,_) ->

        float_of_int n

    | Clink ck' -> aux ck'

    | Ccarrying (_,ck') -> aux ck'

  in

  int_of_float (aux ck)

(** [phase ck] returns the phase of [ck]. It is not expressed as a

    fraction of the period, but instead as an amount of time. Expects a

    constant expression belonging to the correct P_k *)

let phase ck =

  let rec aux ck =

  match ck.cdesc with

  | Carrow (_,_) | Ctuple _ | Con (_,_,_)

  | Cvar _ | Cunivar _ ->

      failwith "internal error: can only compute phase of const pck"

  | Pck_up (ck',_) ->

      aux ck'

  | Pck_down (ck',k) ->

      aux ck'

  | Pck_phase (ck',(a,b)) ->

      let n = period ck' in

      let (a',b') = aux ck' in

      sum_rat (a',b') (n*a,b)

  | Pck_const (n,(a,b)) ->

      (n*a,b)

  | Clink ck' -> aux ck'

  | Ccarrying (_,ck') -> aux ck'

  in

  let (a,b) = aux ck in

  simplify_rat (a,b)

let eq_carrier cr1 cr2 =

  match (carrier_repr cr1).carrier_desc, (carrier_repr cr2).carrier_desc with

 | Carry_const id1, Carry_const id2 -> id1 = id2

 | _                                -> cr1.carrier_id = cr2.carrier_id

let eq_clock ck1 ck2 =

 (repr ck1).cid = (repr ck2).cid

(* Returns the clock root of a clock *)

let rec root ck =

  let ck = repr ck in

  match ck.cdesc with

  | Ctuple (ck'::_)

  | Con (ck',_,_) | Clink ck' | Ccarrying (_,ck') -> root ck'

  | Pck_up _ | Pck_down _ | Pck_phase _ | Pck_const _ | Cvar _ | Cunivar _ -> ck

  | Carrow _ | Ctuple _ -> failwith "Internal error root"

(* Returns the branch of clock [ck] in its clock tree *)

let rec branch ck =

  let rec branch ck acc =

    match (repr ck).cdesc with

    | Ccarrying (_, ck) -> branch ck acc

    | Con (ck, cr, l)   -> branch ck ((cr, l) :: acc)

    | Ctuple (ck::_)    -> branch ck acc

    | Ctuple _

    | Carrow _          -> assert false

    | _                 -> acc

  in branch ck [];;

let clock_of_root_branch r br =

 List.fold_left (fun ck (cr,l) -> new_ck (Con (ck, cr, l)) true) r br

(* Computes the (longest) common prefix of two branches *)

let rec common_prefix br1 br2 =

 match br1, br2 with

 | []          , _

 | _           , []           -> []

 | (cr1,l1)::q1, (cr2,l2)::q2 ->

   if eq_carrier cr1 cr2 && (l1 = l2)

   then (cr1, l1) :: common_prefix q1 q2

   else []

(* Tests whether clock branches [br1] nd [br2] are statically disjoint *)

let rec disjoint_branches br1 br2 =

 match br1, br2 with

 | []          , _

 | _           , []           -> false

 | (cr1,l1)::q1, (cr2,l2)::q2 -> eq_carrier cr1 cr2 && ((l1 <> l2) || disjoint_branches q1 q2);;

(* Disjunction relation between variables based upon their static clocks. *)

let disjoint ck1 ck2 =

  eq_clock (root ck1) (root ck2) && disjoint_branches (branch ck1) (branch ck2)

(** [normalize pck] returns the normal form of clock [pck]. *)

let normalize pck =

  let changed = ref true in

  let rec aux pck =

    match pck.cdesc with

    | Pck_up ({cdesc=Pck_up (pck',k')},k) ->

        changed:=true;

        new_ck (Pck_up (aux pck',k*k')) pck.cscoped

    | Pck_up ({cdesc=Pck_down (pck',k')},k) ->

        changed:=true;

        new_ck (Pck_down (new_ck (Pck_up (aux pck',k)) pck.cscoped,k')) pck.cscoped

    | Pck_up ({cdesc=Pck_phase (pck',(a,b))},k) ->

        changed:=true;

        new_ck (Pck_phase (new_ck (Pck_up (aux pck',k)) pck.cscoped,(a*k,b))) pck.cscoped

    | Pck_down ({cdesc=Pck_down (pck',k')},k) ->

        changed:=true;

        new_ck (Pck_down (aux pck',k*k')) pck.cscoped

    | Pck_down ({cdesc=Pck_phase (pck',(a,b))},k) ->

        changed:=true;

        new_ck (Pck_phase (new_ck (Pck_down (aux pck',k)) pck.cscoped,(a,b*k))) pck.cscoped

    | Pck_phase ({cdesc=Pck_phase (pck',(a',b'))},(a,b)) ->

        changed:=true;

        let (a'',b'') = sum_rat (a,b) (a',b') in

        new_ck (Pck_phase (aux pck',(a'',b''))) pck.cscoped

    | Pck_up (pck',k') ->

        new_ck (Pck_up (aux pck',k')) pck.cscoped

    | Pck_down (pck',k') ->

        new_ck (Pck_down (aux pck',k')) pck.cscoped

    | Pck_phase (pck',k') ->

        new_ck (Pck_phase (aux pck',k')) pck.cscoped

    | Ccarrying (cr,ck') ->

        new_ck (Ccarrying (cr, aux ck')) pck.cscoped

    | _ -> pck

  in

  let nf=ref pck in

  while !changed do

    changed:=false;

    nf:=aux !nf

  done;

  !nf

(** [canonize pck] reduces transformations of [pck] and removes

    identity transformations. Expects a normalized periodic clock ! *)

let canonize pck =

  let rec remove_id_trans pck =

    match pck.cdesc with

    | Pck_up (pck',1) | Pck_down (pck',1) | Pck_phase (pck',(0,_)) ->

        remove_id_trans pck'

    | _ -> pck

  in

  let pck =

    match pck.cdesc with

    | Pck_phase ({cdesc=Pck_down ({cdesc=Pck_up (v,k)},k')},k'') ->

        let gcd = gcd k k' in

        new_ck (Pck_phase

                  (new_ck (Pck_down

                             (new_ck (Pck_up (v,k/gcd)) pck.cscoped,k'/gcd))

                     pck.cscoped,k''))

          pck.cscoped

    | Pck_down ({cdesc=Pck_up (v,k)},k') ->

        let gcd = gcd k k' in

        new_ck (Pck_down (new_ck (Pck_up (v,k/gcd)) pck.cscoped,k'/gcd)) pck.cscoped

    | _ -> pck

  in

  remove_id_trans pck

(** [simplify pck] applies pclocks simplifications to [pck] *)

let simplify pck =

  if (is_concrete_pck pck) then

    let n = period pck in

    let (a,b) = phase pck in

    let phase' = simplify_rat (a,b*n) in 

    new_ck (Pck_const (n,phase')) pck.cscoped

  else

    let pck' = deep_repr pck in

    let nf_pck = normalize pck' in

    canonize nf_pck

let print_cvar fmt cvar =

  match cvar.cdesc with

  | Cvar cset ->

 (*

      if cvar.cscoped

      then

	fprintf fmt "[_%s%a]"

	  (name_of_type cvar.cid)

	  print_ckset cset

      else

 *)

	fprintf fmt "_%s%a"

	  (name_of_type cvar.cid)

	  print_ckset cset

  | Cunivar cset ->

 (*

      if cvar.cscoped

      then

	fprintf fmt "['%s%a]"

	  (name_of_type cvar.cid)

	  print_ckset cset

      else

 *)

	fprintf fmt "'%s%a"

	  (name_of_type cvar.cid)

	  print_ckset cset

  | _ -> failwith "Internal error print_cvar"

(* Nice pretty-printing. Simplifies expressions before printing them. Non-linear

   complexity. *)

let print_ck fmt ck =

  let rec aux fmt ck =

    let ck = simplify ck in

    match ck.cdesc with

    | Carrow (ck1,ck2) ->

      fprintf fmt "%a -> %a" aux ck1 aux ck2

    | Ctuple cklist ->

      fprintf fmt "(%a)" 

	(fprintf_list ~sep:" * " aux) cklist

    | Con (ck,c,l) ->

      fprintf fmt "%a on %s(%a)" aux ck l print_carrier c

    | Pck_up (ck,k) ->

      fprintf fmt "%a*.%i" aux ck k

    | Pck_down (ck,k) ->

      fprintf fmt "%a/.%i" aux ck k

    | Pck_phase (ck,q) ->

      fprintf fmt "%a->.%a" aux ck print_rat (simplify_rat q)

    | Pck_const (n,p) ->

      fprintf fmt "(%i,%a)" n print_rat (simplify_rat p)

    | Cvar cset ->

(*

      if ck.cscoped

      then

        fprintf fmt "[_%s]" (name_of_type ck.cid)

      else

*)

	fprintf fmt "_%s" (name_of_type ck.cid)

    | Cunivar cset ->

(*

      if ck.cscoped

      then

        fprintf fmt "['%s]" (name_of_type ck.cid)

      else

*)

        fprintf fmt "'%s" (name_of_type ck.cid)

    | Clink ck' ->

        aux fmt ck'

    | Ccarrying (cr,ck') ->

      fprintf fmt "(%a:%a)" print_carrier cr aux ck'

  in

  let cvars = constrained_vars_of_clock ck in

  aux fmt ck;

  if cvars <> [] then

    fprintf fmt " (where %a)"

      (fprintf_list ~sep:", " print_cvar) cvars

(* prints only the Con components of a clock, useful for printing nodes *)

let rec print_ck_suffix fmt ck =

  let ck = simplify ck in

  match ck.cdesc with

  | Carrow _

  | Ctuple _

  | Cvar _

  | Cunivar _   -> ()

  | Con (ck,c,l) ->

    fprintf fmt "%a when %s(%a)" print_ck_suffix ck l print_carrier c

  | Clink ck' ->

    print_ck_suffix fmt ck'

  | Ccarrying (cr,ck') ->

    fprintf fmt "%a" print_ck_suffix ck'

  | _ -> assert false

let pp_error fmt = function

  | Clock_clash (ck1,ck2) ->

      reset_names ();

      fprintf fmt "Expected clock %a, got clock %a@."

      print_ck ck1

      print_ck ck2

  | Not_pck ->

    fprintf fmt "The clock of this expression must be periodic@."

  | Carrier_mismatch (cr1, cr2) ->

     fprintf fmt "Name clash. Expected clock %a, got clock %a@."

       print_carrier cr1

       print_carrier cr2

  | Clock_set_mismatch (ck,cset) ->

      reset_names ();

    fprintf fmt "Clock %a is not included in clock set %a@."

      print_ck ck

      print_ckset cset

  | Cannot_be_polymorphic ck ->

      reset_names ();

    fprintf fmt "The main node cannot have a polymorphic clock: %a@."

      print_ck ck

  | Invalid_imported_clock ck ->

      reset_names ();

    fprintf fmt "Not a valid imported node clock: %a@."

      print_ck ck

  | Invalid_const ck ->

      reset_names ();

    fprintf fmt "Clock %a is not a valid periodic clock@."

      print_ck ck;

  | Factor_zero ->

    fprintf fmt "Cannot apply clock transformation with factor 0@."

  | Carrier_extrusion (ck,cr) ->

    fprintf fmt "This node has clock@.%a@.It is invalid as %a escapes its scope@."

      print_ck ck

      print_carrier cr

  | Clock_extrusion (ck_node,ck) ->

    fprintf fmt "This node has clock@.%a@.It is invalid as %a escapes its scope@."

      print_ck ck_node

      print_ck ck

let const_of_carrier cr =

 match (carrier_repr cr).carrier_desc with

 | Carry_const id -> id

 | Carry_name

 | Carry_var

 | Carry_link _ -> (Format.eprintf "internal error: const_of_carrier %a@." print_carrier cr; assert false) (* TODO check this Xavier *)

let uneval const cr =

  (*Format.printf "Clocks.uneval %s %a@." const print_carrier cr;*)

  let cr = carrier_repr cr in

  match cr.carrier_desc with

  | Carry_var -> cr.carrier_desc <- Carry_const const

  | Carry_name -> cr.carrier_desc <- Carry_const const

  | _         -> assert false

(* Local Variables: *)

(* compile-command:"make -C .." *)

(* End: *)