(* Title: HOL/Tools/primrec_package.ML
ID: $Id$
Author: Stefan Berghofer, TU Muenchen and Norbert Voelker, FernUni Hagen
Package for defining functions on datatypes by primitive recursion.
*)
signature PRIMREC_PACKAGE =
sig
val quiet_mode: bool ref
val add_primrec: string -> ((bstring * string) * Attrib.src list) list
-> theory -> theory * thm list
val add_primrec_i: string -> ((bstring * term) * theory attribute list) list
-> theory -> theory * thm list
end;
structure PrimrecPackage : PRIMREC_PACKAGE =
struct
open DatatypeAux;
exception RecError of string;
fun primrec_err s = error ("Primrec definition error:\n" ^ s);
fun primrec_eq_err sign s eq =
primrec_err (s ^ "\nin\n" ^ quote (Sign.string_of_term sign eq));
(* messages *)
val quiet_mode = ref false;
fun message s = if ! quiet_mode then () else writeln s;
(* preprocessing of equations *)
fun process_eqn sign (eq, rec_fns) =
let
val (lhs, rhs) =
if null (term_vars eq) then
HOLogic.dest_eq (HOLogic.dest_Trueprop eq)
handle TERM _ => raise RecError "not a proper equation"
else raise RecError "illegal schematic variable(s)";
val (recfun, args) = strip_comb lhs;
val fnameT = dest_Const recfun handle TERM _ =>
raise RecError "function is not declared as constant in theory";
val (ls', rest) = take_prefix is_Free args;
val (middle, rs') = take_suffix is_Free rest;
val rpos = length ls';
val (constr, cargs') = if null middle then raise RecError "constructor missing"
else strip_comb (hd middle);
val (cname, T) = dest_Const constr
handle TERM _ => raise RecError "ill-formed constructor";
val (tname, _) = dest_Type (body_type T) handle TYPE _ =>
raise RecError "cannot determine datatype associated with function"
val (ls, cargs, rs) = (map dest_Free ls',
map dest_Free cargs',
map dest_Free rs')
handle TERM _ => raise RecError "illegal argument in pattern";
val lfrees = ls @ rs @ cargs;
fun check_vars _ [] = ()
| check_vars s vars = raise RecError (s ^ commas_quote (map fst vars))
in
if length middle > 1 then
raise RecError "more than one non-variable in pattern"
else
(check_vars "repeated variable names in pattern: " (duplicates lfrees);
check_vars "extra variables on rhs: "
(map dest_Free (term_frees rhs) \\ lfrees);
case AList.lookup (op =) rec_fns fnameT of
NONE =>
(fnameT, (tname, rpos, [(cname, (ls, cargs, rs, rhs, eq))]))::rec_fns
| SOME (_, rpos', eqns) =>
if AList.defined (op =) eqns cname then
raise RecError "constructor already occurred as pattern"
else if rpos <> rpos' then
raise RecError "position of recursive argument inconsistent"
else
AList.update (op =) (fnameT, (tname, rpos, (cname, (ls, cargs, rs, rhs, eq))::eqns))
rec_fns)
end
handle RecError s => primrec_eq_err sign s eq;
fun process_fun sign descr rec_eqns ((i, fnameT as (fname, _)), (fnameTs, fnss)) =
let
val (_, (tname, _, constrs)) = List.nth (descr, i);
(* substitute "fname ls x rs" by "y ls rs" for (x, (_, y)) in subs *)
fun subst [] x = x
| subst subs (fs, Abs (a, T, t)) =
let val (fs', t') = subst subs (fs, t)
in (fs', Abs (a, T, t')) end
| subst subs (fs, t as (_ $ _)) =
let val (f, ts) = strip_comb t;
in
if is_Const f andalso dest_Const f mem map fst rec_eqns then
let
val fnameT' as (fname', _) = dest_Const f;
val (_, rpos, _) = the (AList.lookup (op =) rec_eqns fnameT');
val ls = Library.take (rpos, ts);
val rest = Library.drop (rpos, ts);
val (x', rs) = (hd rest, tl rest)
handle Empty => raise RecError ("not enough arguments\
\ in recursive application\nof function " ^ quote fname' ^ " on rhs");
val (x, xs) = strip_comb x'
in
(case AList.lookup (op =) subs x of
NONE =>
let
val (fs', ts') = foldl_map (subst subs) (fs, ts)
in (fs', list_comb (f, ts')) end
| SOME (i', y) =>
let
val (fs', ts') = foldl_map (subst subs) (fs, xs @ ls @ rs);
val fs'' = process_fun sign descr rec_eqns ((i', fnameT'), fs')
in (fs'', list_comb (y, ts'))
end)
end
else
let
val (fs', f'::ts') = foldl_map (subst subs) (fs, f::ts)
in (fs', list_comb (f', ts')) end
end
| subst _ x = x;
(* translate rec equations into function arguments suitable for rec comb *)
fun trans eqns ((cname, cargs), (fnameTs', fnss', fns)) =
(case AList.lookup (op =) eqns cname of
NONE => (warning ("No equation for constructor " ^ quote cname ^
"\nin definition of function " ^ quote fname);
(fnameTs', fnss', (Const ("arbitrary", dummyT))::fns))
| SOME (ls, cargs', rs, rhs, eq) =>
let
val recs = List.filter (is_rec_type o snd) (cargs' ~~ cargs);
val rargs = map fst recs;
val subs = map (rpair dummyT o fst)
(rev (rename_wrt_term rhs rargs));
val ((fnameTs'', fnss''), rhs') =
(subst (map (fn ((x, y), z) =>
(Free x, (body_index y, Free z)))
(recs ~~ subs))
((fnameTs', fnss'), rhs))
handle RecError s => primrec_eq_err sign s eq
in (fnameTs'', fnss'',
(list_abs_free (cargs' @ subs @ ls @ rs, rhs'))::fns)
end)
in (case AList.lookup (op =) fnameTs i of
NONE =>
if exists (equal fnameT o snd) fnameTs then
raise RecError ("inconsistent functions for datatype " ^ quote tname)
else
let
val (_, _, eqns) = the (AList.lookup (op =) rec_eqns fnameT);
val (fnameTs', fnss', fns) = foldr (trans eqns)
((i, fnameT)::fnameTs, fnss, []) constrs
in
(fnameTs', (i, (fname, #1 (snd (hd eqns)), fns))::fnss')
end
| SOME fnameT' =>
if fnameT = fnameT' then (fnameTs, fnss)
else raise RecError ("inconsistent functions for datatype " ^ quote tname))
end;
(* prepare functions needed for definitions *)
fun get_fns fns (((i, (tname, _, constrs)), rec_name), (fs, defs)) =
case AList.lookup (op =) fns i of
NONE =>
let
val dummy_fns = map (fn (_, cargs) => Const ("arbitrary",
replicate ((length cargs) + (length (List.filter is_rec_type cargs)))
dummyT ---> HOLogic.unitT)) constrs;
val _ = warning ("No function definition for datatype " ^ quote tname)
in
(dummy_fns @ fs, defs)
end
| SOME (fname, ls, fs') => (fs' @ fs, (fname, ls, rec_name, tname)::defs);
(* make definition *)
fun make_def sign fs (fname, ls, rec_name, tname) =
let
val rhs = foldr (fn (T, t) => Abs ("", T, t))
(list_comb (Const (rec_name, dummyT),
fs @ map Bound (0 ::(length ls downto 1))))
((map snd ls) @ [dummyT]);
val defpair = (Sign.base_name fname ^ "_" ^ Sign.base_name tname ^ "_def",
Logic.mk_equals (Const (fname, dummyT), rhs))
in Theory.inferT_axm sign defpair end;
(* find datatypes which contain all datatypes in tnames' *)
fun find_dts (dt_info : datatype_info Symtab.table) _ [] = []
| find_dts dt_info tnames' (tname::tnames) =
(case Symtab.lookup dt_info tname of
NONE => primrec_err (quote tname ^ " is not a datatype")
| SOME dt =>
if tnames' subset (map (#1 o snd) (#descr dt)) then
(tname, dt)::(find_dts dt_info tnames' tnames)
else find_dts dt_info tnames' tnames);
fun prepare_induct ({descr, induction, ...}: datatype_info) rec_eqns =
let
fun constrs_of (_, (_, _, cs)) =
map (fn (cname:string, (_, cargs, _, _, _)) => (cname, map fst cargs)) cs;
val params_of = these o AList.lookup (op =) (List.concat (map constrs_of rec_eqns));
in
induction
|> RuleCases.rename_params (map params_of (List.concat (map (map #1 o #3 o #2) descr)))
|> RuleCases.save induction
end;
fun add_primrec_i alt_name eqns_atts thy =
let
val (eqns, atts) = split_list eqns_atts;
val sg = Theory.sign_of thy;
val dt_info = DatatypePackage.get_datatypes thy;
val rec_eqns = foldr (process_eqn sg) [] (map snd eqns);
val tnames = distinct (map (#1 o snd) rec_eqns);
val dts = find_dts dt_info tnames tnames;
val main_fns =
map (fn (tname, {index, ...}) =>
(index,
(fst o the o find_first (fn f => (#1 o snd) f = tname)) rec_eqns))
dts;
val {descr, rec_names, rec_rewrites, ...} =
if null dts then
primrec_err ("datatypes " ^ commas_quote tnames ^ "\nare not mutually recursive")
else snd (hd dts);
val (fnameTs, fnss) = foldr (process_fun sg descr rec_eqns)
([], []) main_fns;
val (fs, defs) = foldr (get_fns fnss) ([], []) (descr ~~ rec_names);
val defs' = map (make_def sg fs) defs;
val nameTs1 = map snd fnameTs;
val nameTs2 = map fst rec_eqns;
val primrec_name =
if alt_name = "" then (space_implode "_" (map (Sign.base_name o #1) defs)) else alt_name;
val (defs_thms', thy') = thy |> Theory.add_path primrec_name |>
(if eq_set (nameTs1, nameTs2) then (PureThy.add_defs_i false o map Thm.no_attributes) defs'
else primrec_err ("functions " ^ commas_quote (map fst nameTs2) ^
"\nare not mutually recursive"));
val rewrites = (map mk_meta_eq rec_rewrites) @ defs_thms';
val _ = message ("Proving equations for primrec function(s) " ^
commas_quote (map fst nameTs1) ^ " ...");
val simps = map (fn (_, t) => standard (Goal.prove thy' [] [] t
(fn _ => EVERY [rewrite_goals_tac rewrites, rtac refl 1]))) eqns;
val (simps', thy'') = PureThy.add_thms ((map fst eqns ~~ simps) ~~ atts) thy';
val thy''' = thy''
|> (snd o PureThy.add_thmss [(("simps", simps'),
[Simplifier.simp_add_global, RecfunCodegen.add NONE])])
|> (snd o PureThy.add_thms [(("induct", prepare_induct (#2 (hd dts)) rec_eqns), [])])
|> Theory.parent_path
in
(thy''', simps')
end;
fun add_primrec alt_name eqns thy =
let
val sign = Theory.sign_of thy;
val ((names, strings), srcss) = apfst split_list (split_list eqns);
val atts = map (map (Attrib.global_attribute thy)) srcss;
val eqn_ts = map (fn s => term_of (Thm.read_cterm sign (s, propT))
handle ERROR => error ("The error(s) above occurred for " ^ s)) strings;
val rec_ts = map (fn eq => head_of (fst (HOLogic.dest_eq (HOLogic.dest_Trueprop eq)))
handle TERM _ => primrec_eq_err sign "not a proper equation" eq) eqn_ts;
val (_, eqn_ts') = InductivePackage.unify_consts (sign_of thy) rec_ts eqn_ts
in
add_primrec_i alt_name (names ~~ eqn_ts' ~~ atts) thy
end;
(* outer syntax *)
local structure P = OuterParse and K = OuterKeyword in
val primrec_decl =
Scan.optional (P.$$$ "(" |-- P.name --| P.$$$ ")") "" --
Scan.repeat1 (P.opt_thm_name ":" -- P.prop);
val primrecP =
OuterSyntax.command "primrec" "define primitive recursive functions on datatypes" K.thy_decl
(primrec_decl >> (fn (alt_name, eqns) =>
Toplevel.theory (#1 o add_primrec alt_name (map P.triple_swap eqns))));
val _ = OuterSyntax.add_parsers [primrecP];
end;
end;