src/Pure/Syntax/syn_trans.ML

Modified functions pt_to_ast and ast_to_term to improve handling
of errors in parse (ast) translations caused by ambiguous input.

(*  Title:      Pure/Syntax/syn_trans.ML
    ID:         $Id$
    Author:     Tobias Nipkow and Markus Wenzel, TU Muenchen
    License:    GPL (GNU GENERAL PUBLIC LICENSE)

Syntax translation functions.
*)

signature SYN_TRANS0 =
sig
  val eta_contract: bool ref
  val atomic_abs_tr': string * typ * term -> term * term
  val mk_binder_tr: string * string -> string * (term list -> term)
  val mk_binder_tr': string * string -> string * (term list -> term)
  val dependent_tr': string * string -> term list -> term
  val antiquote_tr: string -> term -> term
  val quote_tr: string -> term -> term
  val quote_antiquote_tr: string -> string -> string -> string * (term list -> term)
  val antiquote_tr': string -> term -> term
  val quote_tr': string -> term -> term
  val quote_antiquote_tr': string -> string -> string -> string * (term list -> term)
  val mark_bound: string -> term
  val mark_boundT: string * typ -> term
  val variant_abs': string * typ * term -> string * term
end;

signature SYN_TRANS1 =
sig
  include SYN_TRANS0
  val non_typed_tr': (term list -> term) -> bool -> typ -> term list -> term
  val non_typed_tr'': ('a -> term list -> term) -> 'a -> bool -> typ -> term list -> term
  val constrainAbsC: string
  val pure_trfuns:
      (string * (Ast.ast list -> Ast.ast)) list *
      (string * (term list -> term)) list *
      (string * (term list -> term)) list *
      (string * (Ast.ast list -> Ast.ast)) list
  val pure_trfunsT: (string * (bool -> typ -> term list -> term)) list
  val struct_trfuns: string list ->
      (string * (Ast.ast list -> Ast.ast)) list *
      (string * (term list -> term)) list *
      (string * (bool -> typ -> term list -> term)) list *
      (string * (Ast.ast list -> Ast.ast)) list
end;

signature SYN_TRANS =
sig
  include SYN_TRANS1
  val abs_tr': term -> term
  val prop_tr': term -> term
  val appl_ast_tr': Ast.ast * Ast.ast list -> Ast.ast
  val applC_ast_tr': Ast.ast * Ast.ast list -> Ast.ast
  val pts_to_asts: (string -> (Ast.ast list -> Ast.ast) option) -> Parser.parsetree list -> Ast.ast list
  val asts_to_terms: (string -> (term list -> term) option) -> Ast.ast list -> term list
end;

structure SynTrans: SYN_TRANS =
struct


(** parse (ast) translations **)

(* constify *)

fun constify_ast_tr [Ast.Variable c] = Ast.Constant c
  | constify_ast_tr asts = raise Ast.AST ("constify_ast_tr", asts);


(* application *)

fun appl_ast_tr [f, args] = Ast.Appl (f :: Ast.unfold_ast "_args" args)
  | appl_ast_tr asts = raise Ast.AST ("appl_ast_tr", asts);

fun applC_ast_tr [f, args] = Ast.Appl (f :: Ast.unfold_ast "_cargs" args)
  | applC_ast_tr asts = raise Ast.AST ("applC_ast_tr", asts);


(* abstraction *)

fun idtyp_ast_tr (*"_idtyp"*) [x, ty] = Ast.Appl [Ast.Constant SynExt.constrainC, x, ty]
  | idtyp_ast_tr (*"_idtyp"*) asts = raise Ast.AST ("idtyp_ast_tr", asts);

fun lambda_ast_tr (*"_lambda"*) [pats, body] =
      Ast.fold_ast_p "_abs" (Ast.unfold_ast "_pttrns" pats, body)
  | lambda_ast_tr (*"_lambda"*) asts = raise Ast.AST ("lambda_ast_tr", asts);

val constrainAbsC = "_constrainAbs";

fun abs_tr (*"_abs"*) [Free (x, T), body] = Term.absfree (x, T, body)
  | abs_tr (*"_abs"*) (ts as [Const (c, _) $ Free (x, T) $ tT, body]) =
      if c = SynExt.constrainC
        then Lexicon.const constrainAbsC $ Term.absfree (x, T, body) $ tT
      else raise TERM ("abs_tr", ts)
  | abs_tr (*"_abs"*) ts = raise TERM ("abs_tr", ts);


(* nondependent abstraction *)

fun k_tr (*"_K"*) [t] = Abs ("uu", dummyT, Term.incr_boundvars 1 t)
  | k_tr (*"_K"*) ts = raise TERM ("k_tr", ts);


(* binder *)

fun mk_binder_tr (sy, name) =
  let
    fun tr (Free (x, T), t) = Lexicon.const name $ Term.absfree (x, T, t)
      | tr (Const ("_idts", _) $ idt $ idts, t) = tr (idt, tr (idts, t))
      | tr (t1 as Const (c, _) $ Free (x, T) $ tT, t) =
          if c = SynExt.constrainC then
            Lexicon.const name $ (Lexicon.const constrainAbsC $ Term.absfree (x, T, t) $ tT)
          else raise TERM ("binder_tr", [t1, t])
      | tr (t1, t2) = raise TERM ("binder_tr", [t1, t2]);

    fun binder_tr (*sy*) [idts, body] = tr (idts, body)
      | binder_tr (*sy*) ts = raise TERM ("binder_tr", ts);
  in
    (sy, binder_tr)
  end;


(* meta propositions *)

fun aprop_tr (*"_aprop"*) [t] = Lexicon.const SynExt.constrainC $ t $ Lexicon.const "prop"
  | aprop_tr (*"_aprop"*) ts = raise TERM ("aprop_tr", ts);

fun ofclass_tr (*"_ofclass"*) [ty, cls] =
      cls $ (Lexicon.const SynExt.constrainC $ Lexicon.const "TYPE" $
        (Lexicon.const "itself" $ ty))
  | ofclass_tr (*"_ofclass"*) ts = raise TERM ("ofclass_tr", ts);


(* meta implication *)

fun bigimpl_ast_tr (*"_bigimpl"*) [asms, concl] =
      Ast.fold_ast_p "==>" (Ast.unfold_ast "_asms" asms, concl)
  | bigimpl_ast_tr (*"_bigimpl"*) asts = raise Ast.AST ("bigimpl_ast_tr", asts);


(* type reflection *)

fun type_tr (*"_TYPE"*) [ty] =
      Lexicon.const SynExt.constrainC $ Lexicon.const "TYPE" $ (Lexicon.const "itself" $ ty)
  | type_tr (*"_TYPE"*) ts = raise TERM ("type_tr", ts);


(* dddot *)

fun dddot_tr (*"_DDDOT"*) ts = Term.list_comb (Lexicon.var SynExt.dddot_indexname, ts);


(* quote / antiquote *)

fun antiquote_tr name =
  let
    fun tr i ((t as Const (c, _)) $ u) =
          if c = name then tr i u $ Bound i
          else tr i t $ tr i u
      | tr i (t $ u) = tr i t $ tr i u
      | tr i (Abs (x, T, t)) = Abs (x, T, tr (i + 1) t)
      | tr _ a = a;
  in tr 0 end;

fun quote_tr name t = Abs ("s", dummyT, antiquote_tr name (Term.incr_boundvars 1 t));

fun quote_antiquote_tr quoteN antiquoteN name =
  let
    fun tr [t] = Lexicon.const name $ quote_tr antiquoteN t
      | tr ts = raise TERM ("quote_tr", ts);
  in (quoteN, tr) end;


(* indexed syntax *)

fun struct_ast_tr (*"_struct"*) [Ast.Appl [Ast.Constant "_index", ast]] = ast
  | struct_ast_tr (*"_struct"*) asts = Ast.mk_appl (Ast.Constant "_struct") asts;

fun index_ast_tr ast =
  Ast.mk_appl (Ast.Constant "_index") [Ast.mk_appl (Ast.Constant "_struct") [ast]];

fun indexdefault_ast_tr (*"_indexdefault"*) [] =
      index_ast_tr (Ast.Constant "_indexdefault")
  | indexdefault_ast_tr (*"_indexdefault"*) asts =
      raise Ast.AST ("indexdefault_ast_tr", asts);

fun indexnum_ast_tr (*"_indexnum"*) [ast] =
      index_ast_tr (Ast.mk_appl (Ast.Constant "_indexnum") [ast])
  | indexnum_ast_tr (*"_indexnum"*) asts = raise Ast.AST ("indexnum_ast_tr", asts);

fun indexvar_ast_tr (*"_indexvar"*) [] =
      Ast.mk_appl (Ast.Constant "_index") [Ast.Variable "some_index"]
  | indexvar_ast_tr (*"_indexvar"*) asts = raise Ast.AST ("indexvar_ast_tr", asts);

fun index_tr (*"_index"*) [t] = t
  | index_tr (*"_index"*) ts = raise TERM ("index_tr", ts);


(* implicit structures *)

fun the_struct structs i =
  if 1 <= i andalso i <= length structs then Library.nth_elem (i - 1, structs)
  else raise ERROR_MESSAGE ("Illegal reference to implicit structure #" ^ string_of_int i);

fun struct_tr structs (*"_struct"*) [Const ("_indexdefault", _)] =
      Lexicon.free (the_struct structs 1)
  | struct_tr structs (*"_struct"*) [t as (Const ("_indexnum", _) $ Const (s, _))] =
      Lexicon.free (the_struct structs
        (case Lexicon.read_nat s of Some n => n | None => raise TERM ("struct_tr", [t])))
  | struct_tr _ (*"_struct"*) ts = raise TERM ("struct_tr", ts);



(** print (ast) translations **)

(* types *)

fun non_typed_tr' f _ _ ts = f ts;
fun non_typed_tr'' f x _ _ ts = f x ts;


(* application *)

fun appl_ast_tr' (f, []) = raise Ast.AST ("appl_ast_tr'", [f])
  | appl_ast_tr' (f, args) = Ast.Appl [Ast.Constant "_appl", f, Ast.fold_ast "_args" args];

fun applC_ast_tr' (f, []) = raise Ast.AST ("applC_ast_tr'", [f])
  | applC_ast_tr' (f, args) = Ast.Appl [Ast.Constant "_applC", f, Ast.fold_ast "_cargs" args];


(* abstraction *)

fun mark_boundT x_T = Lexicon.const "_bound" $ Free x_T;
fun mark_bound x = mark_boundT (x, dummyT);

fun strip_abss vars_of body_of tm =
  let
    val vars = vars_of tm;
    val body = body_of tm;
    val rev_new_vars = rename_wrt_term body vars;
  in
    (map mark_boundT (rev rev_new_vars),
      subst_bounds (map (mark_bound o #1) rev_new_vars, body))
  end;


(*do (partial) eta-contraction before printing*)

val eta_contract = ref true;

fun eta_contr tm =
  let
    fun is_aprop (Const ("_aprop", _)) = true
      | is_aprop _ = false;

    fun eta_abs (Abs (a, T, t)) =
          (case eta_abs t of
            t' as f $ u =>
              (case eta_abs u of
                Bound 0 =>
                  if Term.loose_bvar1 (f, 0) orelse is_aprop f then Abs (a, T, t')
                  else  incr_boundvars ~1 f
              | _ => Abs (a, T, t'))
          | t' => Abs (a, T, t'))
      | eta_abs t = t;
  in
    if ! eta_contract then eta_abs tm else tm
  end;


fun abs_tr' tm =
  foldr (fn (x, t) => Lexicon.const "_abs" $ x $ t)
    (strip_abss strip_abs_vars strip_abs_body (eta_contr tm));

fun atomic_abs_tr' (x, T, t) =
  let val [xT] = rename_wrt_term t [(x, T)]
  in (mark_boundT xT, subst_bound (mark_bound (fst xT), t)) end;

fun abs_ast_tr' (*"_abs"*) asts =
  (case Ast.unfold_ast_p "_abs" (Ast.Appl (Ast.Constant "_abs" :: asts)) of
    ([], _) => raise Ast.AST ("abs_ast_tr'", asts)
  | (xs, body) => Ast.Appl [Ast.Constant "_lambda", Ast.fold_ast "_pttrns" xs, body]);


(* binder *)

fun mk_binder_tr' (name, sy) =
  let
    fun mk_idts [] = raise Match    (*abort translation*)
      | mk_idts [idt] = idt
      | mk_idts (idt :: idts) = Lexicon.const "_idts" $ idt $ mk_idts idts;

    fun tr' t =
      let
        val (xs, bd) = strip_abss (strip_qnt_vars name) (strip_qnt_body name) t;
      in Lexicon.const sy $ mk_idts xs $ bd end;

    fun binder_tr' (*name*) (t :: ts) = Term.list_comb (tr' (Lexicon.const name $ t), ts)
      | binder_tr' (*name*) [] = raise Match;
  in
    (name, binder_tr')
  end;


(* idtyp constraints *)

fun idtyp_ast_tr' a [Ast.Appl [Ast.Constant c, x, ty], xs] =
      if c = SynExt.constrainC then
        Ast.Appl [ Ast.Constant a,  Ast.Appl [Ast.Constant "_idtyp", x, ty], xs]
      else raise Match
  | idtyp_ast_tr' _ _ = raise Match;


(* meta propositions *)

fun prop_tr' tm =
  let
    fun aprop t = Lexicon.const "_aprop" $ t;

    fun is_prop Ts t =
      fastype_of1 (Ts, t) = propT handle TERM _ => false;

    fun tr' _ (t as Const _) = t
      | tr' _ (t as Free (x, T)) =
          if T = propT then aprop (Lexicon.free x) else t
      | tr' _ (t as Var (xi, T)) =
          if T = propT then aprop (Lexicon.var xi) else t
      | tr' Ts (t as Bound _) =
          if is_prop Ts t then aprop t else t
      | tr' Ts (Abs (x, T, t)) = Abs (x, T, tr' (T :: Ts) t)
      | tr' Ts (t as t1 $ (t2 as Const ("TYPE", Type ("itself", [T])))) =
          if is_prop Ts t then Const ("_mk_ofclass", T) $ tr' Ts t1
          else tr' Ts t1 $ tr' Ts t2
      | tr' Ts (t as t1 $ t2) =
          (if is_Const (Term.head_of t) orelse not (is_prop Ts t)
            then I else aprop) (tr' Ts t1 $ tr' Ts t2);
  in
    tr' [] tm
  end;

fun mk_ofclass_tr' show_sorts (*"_mk_ofclass"*) T [t] =
      Lexicon.const "_ofclass" $ TypeExt.term_of_typ show_sorts T $ t
  | mk_ofclass_tr' _ (*"_mk_ofclass"*) T ts = raise TYPE ("mk_ofclass_tr'", [T], ts);


(* meta implication *)

fun impl_ast_tr' (*"==>"*) asts =
  if TypeExt.no_brackets () then raise Match
  else
    (case Ast.unfold_ast_p "==>" (Ast.Appl (Ast.Constant "==>" :: asts)) of
      (asms as _ :: _ :: _, concl)
        => Ast.Appl [Ast.Constant "_bigimpl", Ast.fold_ast "_asms" asms, concl]
    | _ => raise Match);


(* meta conjunction *)

fun meta_conjunction_tr' (*"all"*)
      [Abs (_, _, Const ("==>", _) $
        (Const ("==>", _) $ A $ (Const ("==>", _) $ B $ (Const ("_aprop", _) $ Bound 0))) $
        (Const ("_aprop", _) $ Bound 0))] =
      if 0 mem_int Term.loose_bnos A orelse 0 mem_int Term.loose_bnos B then raise Match
      else Lexicon.const "_meta_conjunction" $ A $ B
  | meta_conjunction_tr' (*"all"*) ts = raise Match;


(* type reflection *)

fun type_tr' show_sorts (*"TYPE"*) (Type ("itself", [T])) ts =
      Term.list_comb (Lexicon.const "_TYPE" $ TypeExt.term_of_typ show_sorts T, ts)
  | type_tr' _ _ _ = raise Match;


(* dependent / nondependent quantifiers *)

fun variant_abs' (x, T, B) =
  let val x' = variant (add_term_names (B, [])) x in
    (x', subst_bound (mark_boundT (x', T), B))
  end;

fun dependent_tr' (q, r) (A :: Abs (x, T, B) :: ts) =
      if Term.loose_bvar1 (B, 0) then
        let val (x', B') = variant_abs' (x, dummyT, B);
        in Term.list_comb (Lexicon.const q $ mark_boundT (x', T) $ A $ B', ts) end
      else Term.list_comb (Lexicon.const r $ A $ B, ts)
  | dependent_tr' _ _ = raise Match;


(* quote / antiquote *)

fun antiquote_tr' name =
  let
    fun tr' i (t $ u) =
      if u = Bound i then Lexicon.const name $ tr' i t
      else tr' i t $ tr' i u
      | tr' i (Abs (x, T, t)) = Abs (x, T, tr' (i + 1) t)
      | tr' i a = if a = Bound i then raise Match else a;
  in tr' 0 end;

fun quote_tr' name (Abs (_, _, t)) = Term.incr_boundvars ~1 (antiquote_tr' name t)
  | quote_tr' _ _ = raise Match;

fun quote_antiquote_tr' quoteN antiquoteN name =
  let
    fun tr' (t :: ts) = Term.list_comb (Lexicon.const quoteN $ quote_tr' antiquoteN t, ts)
      | tr' _ = raise Match;
  in (name, tr') end;


(* indexed syntax *)

fun index_ast_tr' (*"_index"*) [Ast.Appl [Ast.Constant "_struct", ast]] = ast
  | index_ast_tr' _ = raise Match;


(* implicit structures *)

fun the_struct' structs s =
  [(case Lexicon.read_nat s of
    Some i => Ast.Variable (the_struct structs i handle ERROR_MESSAGE _ => raise Match)
  | None => raise Match)] |> Ast.mk_appl (Ast.Constant "_free");
;

fun struct_ast_tr' structs (*"_struct"*) [Ast.Constant "_indexdefault"] =
      the_struct' structs "1"
  | struct_ast_tr' structs (*"_struct"*) [Ast.Appl [Ast.Constant "_indexnum", Ast.Constant s]] =
      the_struct' structs s
  | struct_ast_tr' _ _ = raise Match;



(** Pure translations **)

val pure_trfuns =
 ([("_constify", constify_ast_tr), ("_appl", appl_ast_tr), ("_applC", applC_ast_tr),
   ("_lambda", lambda_ast_tr), ("_idtyp", idtyp_ast_tr), ("_bigimpl", bigimpl_ast_tr),
   ("_indexdefault", indexdefault_ast_tr), ("_indexnum", indexnum_ast_tr),
   ("_indexvar", indexvar_ast_tr), ("_struct", struct_ast_tr)],
  [("_abs", abs_tr), ("_aprop", aprop_tr), ("_ofclass", ofclass_tr),
   ("_TYPE", type_tr), ("_DDDOT", dddot_tr), ("_K", k_tr),
   ("_index", index_tr)],
  [("all", meta_conjunction_tr')],
  [("_abs", abs_ast_tr'), ("_idts", idtyp_ast_tr' "_idts"),
   ("_pttrns", idtyp_ast_tr' "_pttrns"), ("==>", impl_ast_tr'),
   ("_index", index_ast_tr')]);

val pure_trfunsT =
  [("_mk_ofclass", mk_ofclass_tr'), ("TYPE", type_tr')];

fun struct_trfuns structs =
  ([], [("_struct", struct_tr structs)], [], [("_struct", struct_ast_tr' structs)]);



exception TRANSLATION of string * exn

(** pts_to_asts **)

fun pts_to_asts trf pts =
  let
    fun trans a args =
      (case trf a of
        None => Ast.mk_appl (Ast.Constant a) args
      | Some f => f args handle exn => raise TRANSLATION (a, exn));

    (*translate pt bottom-up*)
    fun ast_of (Parser.Node (a, pts)) = trans a (map ast_of pts)
      | ast_of (Parser.Tip tok) = Ast.Variable (Lexicon.str_of_token tok);

    val exn_results =
      map (fn pt => Result (ast_of pt) handle exn => Exn exn) pts;
    val exns = mapfilter get_exn exn_results;
    val results = mapfilter get_result exn_results
  in
    case results of
      [] => (case exns of
        TRANSLATION (a, exn) :: _ =>
          (writeln ("Error in parse ast translation for " ^ quote a); raise exn)
      | _ => [])
    | _ => results
  end;



(** asts_to_terms **)

fun asts_to_terms trf asts =
  let
    fun trans a args =
      (case trf a of
        None => Term.list_comb (Lexicon.const a, args)
      | Some f => f args handle exn => raise TRANSLATION (a, exn));

    fun term_of (Ast.Constant a) = trans a []
      | term_of (Ast.Variable x) = Lexicon.read_var x
      | term_of (Ast.Appl (Ast.Constant a :: (asts as _ :: _))) =
          trans a (map term_of asts)
      | term_of (Ast.Appl (ast :: (asts as _ :: _))) =
          Term.list_comb (term_of ast, map term_of asts)
      | term_of (ast as Ast.Appl _) = raise Ast.AST ("ast_to_term: malformed ast", [ast]);

    val exn_results =
      map (fn t => Result (term_of t) handle exn => Exn exn) asts;
    val exns = mapfilter get_exn exn_results;
    val results = mapfilter get_result exn_results
  in
    case results of
      [] => (case exns of
        TRANSLATION (a, exn) :: _ =>
          (writeln ("Error in parse translation for " ^ quote a); raise exn)
      | _ => [])
    | _ => results
  end;

end;