src/HOL/Tools/recfun_codegen.ML
author wenzelm
Tue May 07 14:26:32 2002 +0200 (2002-05-07)
changeset 13105 3d1e7a199bdc
parent 12556 5e2593ef0a44
child 14196 be5e838f37bd
permissions -rw-r--r--
use eq_thm_prop instead of slightly inadequate eq_thm;
     1 (*  Title:      HOL/recfun_codegen.ML
     2     ID:         $Id$
     3     Author:     Stefan Berghofer, TU Muenchen
     4     License:    GPL (GNU GENERAL PUBLIC LICENSE)
     5 
     6 Code generator for recursive functions.
     7 *)
     8 
     9 signature RECFUN_CODEGEN =
    10 sig
    11   val add: theory attribute
    12   val setup: (theory -> theory) list
    13 end;
    14 
    15 structure RecfunCodegen : RECFUN_CODEGEN =
    16 struct
    17 
    18 open Codegen;
    19 
    20 structure CodegenArgs =
    21 struct
    22   val name = "HOL/recfun_codegen";
    23   type T = thm list Symtab.table;
    24   val empty = Symtab.empty;
    25   val copy = I;
    26   val prep_ext = I;
    27   val merge = Symtab.merge_multi Drule.eq_thm_prop;
    28   fun print _ _ = ();
    29 end;
    30 
    31 structure CodegenData = TheoryDataFun(CodegenArgs);
    32 
    33 val prop_of = #prop o rep_thm;
    34 val dest_eqn = HOLogic.dest_eq o HOLogic.dest_Trueprop;
    35 val const_of = dest_Const o head_of o fst o dest_eqn;
    36 
    37 fun warn thm = warning ("RecfunCodegen: Not a proper equation:\n" ^
    38   string_of_thm thm);
    39 
    40 fun add (p as (thy, thm)) =
    41   let
    42     val tsig = Sign.tsig_of (sign_of thy);
    43     val tab = CodegenData.get thy;
    44     val (s, _) = const_of (prop_of thm);
    45 
    46     val matches = curry
    47       (Pattern.matches tsig o pairself (fst o dest_eqn o prop_of));
    48 
    49   in (CodegenData.put (Symtab.update ((s,
    50     filter_out (matches thm) (if_none (Symtab.lookup (tab, s)) []) @ [thm]),
    51       tab)) thy, thm)
    52   end handle TERM _ => (warn thm; p) | Pattern.Pattern => (warn thm; p);
    53 
    54 fun get_equations thy (s, T) =
    55   (case Symtab.lookup (CodegenData.get thy, s) of
    56      None => []
    57    | Some thms => filter (fn thm => is_instance thy T
    58        (snd (const_of (prop_of thm)))) thms);
    59 
    60 fun mk_poly_id thy (s, T) = mk_const_id (sign_of thy) s ^
    61   (case get_defn thy s T of
    62      Some (_, Some i) => "_def" ^ string_of_int i
    63    | _ => "");
    64 
    65 exception EQN of string * typ * string;
    66 
    67 fun cycle g (xs, x) =
    68   if x mem xs then xs
    69   else foldl (cycle g) (x :: xs, flat (Graph.find_paths g (x, x)));
    70 
    71 fun add_rec_funs thy gr dep eqs =
    72   let
    73     fun dest_eq t =
    74       (mk_poly_id thy (const_of t), dest_eqn (rename_term t));
    75     val eqs' = map dest_eq eqs;
    76     val (dname, _) :: _ = eqs';
    77     val (s, T) = const_of (hd eqs);
    78 
    79     fun mk_fundef fname prfx gr [] = (gr, [])
    80       | mk_fundef fname prfx gr ((fname', (lhs, rhs)) :: xs) =
    81       let
    82         val (gr1, pl) = invoke_codegen thy dname false (gr, lhs);
    83         val (gr2, pr) = invoke_codegen thy dname false (gr1, rhs);
    84         val (gr3, rest) = mk_fundef fname' "and " gr2 xs
    85       in
    86         (gr3, Pretty.blk (4, [Pretty.str (if fname = fname' then "  | " else prfx),
    87            pl, Pretty.str " =", Pretty.brk 1, pr]) :: rest)
    88       end;
    89 
    90     fun put_code fundef = Graph.map_node dname
    91       (K (Some (EQN ("", dummyT, dname)), Pretty.string_of (Pretty.blk (0,
    92       separate Pretty.fbrk fundef @ [Pretty.str ";"])) ^ "\n\n"));
    93 
    94   in
    95     (case try (Graph.get_node gr) dname of
    96        None =>
    97          let
    98            val gr1 = Graph.add_edge (dname, dep)
    99              (Graph.new_node (dname, (Some (EQN (s, T, "")), "")) gr);
   100            val (gr2, fundef) = mk_fundef "" "fun " gr1 eqs';
   101            val xs = cycle gr2 ([], dname);
   102            val cs = map (fn x => case Graph.get_node gr2 x of
   103                (Some (EQN (s, T, _)), _) => (s, T)
   104              | _ => error ("RecfunCodegen: illegal cyclic dependencies:\n" ^
   105                 implode (separate ", " xs))) xs
   106          in (case xs of
   107              [_] => put_code fundef gr2
   108            | _ =>
   109              if not (dep mem xs) then
   110                let
   111                  val eqs'' = map (dest_eq o prop_of)
   112                    (flat (map (get_equations thy) cs));
   113                  val (gr3, fundef') = mk_fundef "" "fun "
   114                    (Graph.add_edge (dname, dep)
   115                      (foldr (uncurry Graph.new_node) (map (fn k =>
   116                        (k, (Some (EQN ("", dummyT, dname)), ""))) xs,
   117                          Graph.del_nodes xs gr2))) eqs''
   118                in put_code fundef' gr3 end
   119              else gr2)
   120          end
   121      | Some (Some (EQN (_, _, s)), _) =>
   122          if s = "" then
   123            if dname = dep then gr else Graph.add_edge (dname, dep) gr
   124          else if s = dep then gr else Graph.add_edge (s, dep) gr)
   125   end;
   126 
   127 fun recfun_codegen thy gr dep brack t = (case strip_comb t of
   128     (Const p, ts) => (case get_equations thy p of
   129        [] => None
   130      | eqns =>
   131         let val (gr', ps) = foldl_map (invoke_codegen thy dep true) (gr, ts)
   132         in
   133           Some (add_rec_funs thy gr' dep (map prop_of eqns),
   134             mk_app brack (Pretty.str (mk_poly_id thy p)) ps)
   135         end)
   136   | _ => None);
   137 
   138 
   139 val setup =
   140   [CodegenData.init,
   141    add_codegen "recfun" recfun_codegen,
   142    add_attribute "" add];
   143 
   144 end;