# HG changeset patch
# User berghofe
# Date 1007994730 -3600
# Node ID e752c9aecdece94ea46dc2c9f06801a7f4c6428a
# Parent  86887b40aeb1c1240242ecc361075980d6292131
Code generator for recursive functions.

diff -r 86887b40aeb1 -r e752c9aecdec src/HOL/Tools/recfun_codegen.ML
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/Tools/recfun_codegen.ML	Mon Dec 10 15:32:10 2001 +0100
@@ -0,0 +1,146 @@
+(*  Title:      HOL/recfun_codegen.ML
+    ID:         $Id$
+    Author:     Stefan Berghofer, TU Muenchen
+    License:    GPL (GNU GENERAL PUBLIC LICENSE)
+
+Code generator for recursive functions.
+*)
+
+signature RECFUN_CODEGEN =
+sig
+  val add: theory attribute
+  val setup: (theory -> theory) list
+end;
+
+structure RecfunCodegen : RECFUN_CODEGEN =
+struct
+
+open Codegen;
+
+structure RecfunArgs =
+struct
+  val name = "HOL/recfun_codegen";
+  type T = thm list Symtab.table;
+  val empty = Symtab.empty;
+  val copy = I;
+  val prep_ext = I;
+  val merge = Symtab.merge_multi eq_thm;
+  fun print _ _ = ();
+end;
+
+structure RecfunData = TheoryDataFun(RecfunArgs);
+
+val prop_of = #prop o rep_thm;
+val dest_eqn = HOLogic.dest_eq o HOLogic.dest_Trueprop;
+val const_of = dest_Const o head_of o fst o dest_eqn;
+
+fun warn thm = warning ("RecfunCodegen: Not a proper equation:\n" ^
+  string_of_thm thm);
+
+fun add (p as (thy, thm)) =
+  let
+    val tsig = Sign.tsig_of (sign_of thy);
+    val tab = RecfunData.get thy;
+    val (s, _) = const_of (prop_of thm);
+
+    val matches = curry
+      (Pattern.matches tsig o pairself (fst o dest_eqn o prop_of));
+
+  in (RecfunData.put (Symtab.update ((s,
+    filter_out (matches thm) (if_none (Symtab.lookup (tab, s)) []) @ [thm]),
+      tab)) thy, thm)
+  end handle TERM _ => (warn thm; p) | Pattern.Pattern => (warn thm; p);
+
+fun get_equations thy (s, T) =
+  (case Symtab.lookup (RecfunData.get thy, s) of
+     None => []
+   | Some thms => filter (fn thm => is_instance thy T
+       (snd (const_of (prop_of thm)))) thms);
+
+fun mk_poly_id thy (s, T) = mk_const_id (sign_of thy) s ^
+  (case get_defn thy s T of
+     Some (_, Some i) => "_def" ^ string_of_int i
+   | _ => "");
+
+exception EQN of string * typ * string;
+
+fun cycle g (xs, x) =
+  if x mem xs then xs
+  else foldl (cycle g) (x :: xs, flat (Graph.find_paths g (x, x)));
+
+fun add_rec_funs thy gr dep eqs =
+  let
+    fun dest_eq t =
+      (mk_poly_id thy (const_of t), dest_eqn (rename_term t));
+    val eqs' = map dest_eq eqs;
+    val (dname, _) :: _ = eqs';
+    val (s, T) = const_of (hd eqs);
+
+    fun mk_fundef fname prfx gr [] = (gr, [])
+      | mk_fundef fname prfx gr ((fname', (lhs, rhs)) :: xs) =
+      let
+        val (gr1, pl) = invoke_codegen thy dname false (gr, lhs);
+        val (gr2, pr) = invoke_codegen thy dname false (gr1, rhs);
+        val (gr3, rest) = mk_fundef fname' "and " gr2 xs
+      in
+        (gr3, Pretty.blk (4, [Pretty.str (if fname = fname' then "  | " else prfx),
+           pl, Pretty.str " =", Pretty.brk 1, pr]) :: rest)
+      end;
+
+    fun put_code fundef = Graph.map_node dname
+      (K (Some (EQN ("", dummyT, dname)), Pretty.string_of (Pretty.blk (0,
+      separate Pretty.fbrk fundef @ [Pretty.str ";"])) ^ "\n\n"));
+
+  in
+    (case try (Graph.get_node gr) dname of
+       None =>
+         let
+           val gr1 = Graph.add_edge (dname, dep)
+             (Graph.new_node (dname, (Some (EQN (s, T, "")), "")) gr);
+           val (gr2, fundef) = mk_fundef "" "fun " gr1 eqs';
+           val xs = cycle gr2 ([], dname);
+           val cs = map (fn x => case Graph.get_node gr2 x of
+               (Some (EQN (s, T, _)), _) => (s, T)
+             | _ => error ("RecfunCodegen: illegal cyclic dependencies:\n" ^
+                implode (separate ", " xs))) xs
+         in (case xs of
+             [_] => put_code fundef gr2
+           | _ =>
+             if not (dep mem xs) then
+               let
+                 val eqs'' = map (dest_eq o prop_of)
+                   (flat (map (get_equations thy) cs));
+                 val (gr3, fundef') = mk_fundef "" "fun "
+                   (Graph.add_edge (dname, dep)
+                     (foldr (uncurry Graph.new_node) (map (fn k =>
+                       (k, (Some (EQN ("", dummyT, dname)), ""))) xs,
+                         Graph.del_nodes xs gr2))) eqs''
+               in put_code fundef' gr3 end
+             else gr2)
+         end
+     | Some (Some (EQN (_, _, s)), _) =>
+         if s = "" then
+           if dname = dep then gr else Graph.add_edge (dname, dep) gr
+         else if s = dep then gr else Graph.add_edge (s, dep) gr)
+  end;
+
+fun recfun_codegen thy gr dep brack t = (case strip_comb t of
+    (Const p, ts) => (case get_equations thy p of
+       [] => None
+     | eqns =>
+        let val (gr', ps) = foldl_map (invoke_codegen thy dep true) (gr, ts)
+        in
+          Some (add_rec_funs thy gr' dep (map prop_of eqns),
+            mk_app brack (Pretty.str (mk_poly_id thy p)) ps)
+        end)
+  | _ => None);
+
+
+val setup =
+  [RecfunData.init,
+   add_codegen "recfun" recfun_codegen,
+   Attrib.add_attributes [("code",
+     (Attrib.no_args add, Attrib.no_args Attrib.undef_local_attribute),
+     "declare equations to be used for code generation")]];
+
+end;