(********* INSTANTIATE ****************************************************)

(* existential_type gives the type of an existential *)
let existential_type env k = 
  let (sp,args) = destConst k in
  let evd = Evd.map (evar_map env) sp in
  instantiate_constr 
    (ids_of_sign evd.evar_hyps) evd.evar_concl.body (Array.to_list args)

(* existential_value gives the value of a defined existential *)
let existential_value env k =
  let (sp,args) = destConst k in
  if defined_const env k then
    let evd = Evd.map (evar_map env) sp in
    match evd.evar_body with
      | EVAR_DEFINED c ->
 	  instantiate_constr (ids_of_sign evd.evar_hyps) c (Array.to_list args)
      | _ -> anomalylabstrm "termenv__existential_value"
            [< 'sTR"The existential variable code just registered a" ;
               'sPC ; 'sTR"grave internal error." >]
  else 
    failwith "undefined existential"


(******* REDUCTION ********************************************************)


(************ REDUCTION.MLI **********************************************)

(*********** TYPEOPS *****************************************************)


(* Constants or existentials. *)

let type_of_constant_or_existential env c =
  if is_existential c then
    type_of_existential env c
  else
    type_of_constant env c


(******** TYPING **********************************************************)

    | IsMeta n ->
       	let metaty =
          try lookup_meta n env
          with Not_found -> error "A variable remains non instanciated" 
	in
        (match kind_of_term metaty with
           | IsCast (typ,kind) -> 
	       ({ uj_val = cstr; uj_type = typ; uj_kind = kind }, cst0)
           | _ ->
	       let (jty,cst) = execute mf env metaty in
	       let k = whd_betadeltaiotaeta env jty.uj_type in
	       ({ uj_val = cstr; uj_type = metaty; uj_kind = k }, cst))