(*  Title:      Pure/codegen.ML

    ID:         $Id$

    Author:     Stefan Berghofer, TU Muenchen

    License:    GPL (GNU GENERAL PUBLIC LICENSE)

Generic code generator.

*)

signature CODEGEN =

sig

  val quiet_mode : bool ref

  val message : string -> unit

  datatype mixfix =

      Arg

    | Ignore

    | Pretty of Pretty.T

    | Term of term;

  val add_codegen: string ->

    (theory -> (exn option * string) Graph.T -> string -> bool -> term ->

    ((exn option * string) Graph.T * Pretty.T) option) -> theory -> theory

  val print_codegens: theory -> unit

  val generate_code: theory -> (string * string) list -> string

  val generate_code_i: theory -> (string * term) list -> string

  val assoc_consts: (xstring * string option * mixfix list) list -> theory -> theory

  val assoc_consts_i: (xstring * typ option * mixfix list) list -> theory -> theory

  val assoc_types: (xstring * string) list -> theory -> theory

  val get_assoc_code: theory -> string -> typ -> mixfix list option

  val get_assoc_types: theory -> (string * string) list

  val invoke_codegen: theory -> (exn option * string) Graph.T ->

    string -> bool -> term -> (exn option * string) Graph.T * Pretty.T

  val mk_const_id: Sign.sg -> string -> string

  val mk_type_id: Sign.sg -> string -> string

  val rename_term: term -> term

  val get_defn: theory -> string -> typ -> ((term list * term) * int option) option

  val is_instance: theory -> typ -> typ -> bool

  val parens: Pretty.T -> Pretty.T

  val mk_app: bool -> Pretty.T -> Pretty.T list -> Pretty.T

  val eta_expand: term -> term list -> int -> term

  val parsers: OuterSyntax.parser list

  val setup: (theory -> theory) list

end;

structure Codegen : CODEGEN =

struct

val quiet_mode = ref true;

fun message s = if !quiet_mode then () else writeln s;

(**** Mixfix syntax ****)

datatype mixfix =

    Arg

  | Ignore

  | Pretty of Pretty.T

  | Term of term;

fun is_arg Arg = true

  | is_arg Ignore = true

  | is_arg _ = false;

fun terms_of [] = []

  | terms_of (Term t :: ms) = t :: terms_of ms

  | terms_of (_ :: ms) = terms_of ms;

val num_args = length o filter is_arg;

(**** theory data ****)

(* data kind 'Pure/codegen' *)

structure CodegenArgs =

struct

  val name = "Pure/codegen";

  type T =

    {codegens : (string * (theory -> (exn option * string) Graph.T -> string ->

       bool -> term -> ((exn option * string) Graph.T * Pretty.T) option)) list,

     consts : ((string * typ) * mixfix list) list,

     types : (string * string) list};

  val empty = {codegens = [], consts = [], types = []};

  val copy = I;

  val prep_ext = I;

  fun merge ({codegens = codegens1, consts = consts1, types = types1},

             {codegens = codegens2, consts = consts2, types = types2}) =

    {codegens = rev (merge_alists (rev codegens1) (rev codegens2)),

     consts   = merge_alists consts1 consts2,

     types    = merge_alists types1 types2};

  fun print sg (cs:T) = Pretty.writeln

    (Pretty.strs ("code generators:" :: map fst (#codegens cs)));

end;

structure CodegenData = TheoryDataFun(CodegenArgs);

val print_codegens = CodegenData.print;

(**** add new code generator to theory ****)

fun add_codegen name f thy =

  let val {codegens, consts, types} = CodegenData.get thy

  in (case assoc (codegens, name) of

      None => CodegenData.put {codegens = (name, f)::codegens,

        consts = consts, types = types} thy

    | Some _ => error ("Code generator " ^ name ^ " already declared"))

  end;

(**** associate constants with target language code ****)

fun gen_assoc_consts prep_type xs thy = foldl (fn (thy, (s, tyopt, syn)) =>

  let

    val sg = sign_of thy;

    val {codegens, consts, types} = CodegenData.get thy;

    val cname = Sign.intern_const sg s;

  in

    (case Sign.const_type sg cname of

       Some T =>

         let val T' = (case tyopt of

                None => T

              | Some ty =>

                  let val U = prep_type sg ty

                  in if Type.typ_instance (Sign.tsig_of sg, U, T) then U

                    else error ("Illegal type constraint for constant " ^ cname)

                  end)

         in (case assoc (consts, (cname, T')) of

             None => CodegenData.put {codegens = codegens,

               consts = ((cname, T'), syn) :: consts, types = types} thy

           | Some _ => error ("Constant " ^ cname ^ " already associated with code"))

         end

     | _ => error ("Not a constant: " ^ s))

  end) (thy, xs);

val assoc_consts_i = gen_assoc_consts (K I);

val assoc_consts = gen_assoc_consts (fn sg => typ_of o read_ctyp sg);

(**** associate types with target language types ****)

fun assoc_types xs thy = foldl (fn (thy, (s, syn)) =>

  let

    val {codegens, consts, types} = CodegenData.get thy;

    val tc = Sign.intern_tycon (sign_of thy) s

  in

    (case assoc (types, tc) of

       None => CodegenData.put {codegens = codegens, consts = consts,

         types = (tc, syn) :: types} thy

     | Some _ => error ("Type " ^ tc ^ " already associated with code"))

  end) (thy, xs);

fun get_assoc_types thy = #types (CodegenData.get thy);

(**** retrieve definition of constant ****)

fun is_instance thy T1 T2 =

  Type.typ_instance (Sign.tsig_of (sign_of thy), T1, Type.varifyT T2);

fun get_assoc_code thy s T = apsome snd (find_first (fn ((s', T'), _) =>

  s = s' andalso is_instance thy T T') (#consts (CodegenData.get thy)));

fun get_defn thy s T =

  let

    val axms = flat (map (Symtab.dest o #axioms o Theory.rep_theory)

      (thy :: Theory.ancestors_of thy));

    val defs = mapfilter (fn (_, t) =>

      (let

         val (lhs, rhs) = Logic.dest_equals t;

         val (c, args) = strip_comb lhs;

         val (s', T') = dest_Const c

       in if s=s' then Some (T', (args, rhs)) else None end) handle TERM _ =>

         None) axms;

    val i = find_index (is_instance thy T o fst) defs

  in

    if i>=0 then Some (snd (nth_elem (i, defs)),

      if length defs = 1 then None else Some i)

    else None

  end;

(**** make valid ML identifiers ****)

fun gen_mk_id kind rename sg s =

  let

    val (xs as x::_) = explode (rename (space_implode "_"

      (NameSpace.unpack (Sign.cond_extern sg kind s))));

    fun check_str [] = ""

      | check_str (x::xs) =

          (if Symbol.is_letter x orelse Symbol.is_digit x orelse x="_" then x

           else "_" ^ string_of_int (ord x)) ^ check_str xs

  in

    (if not (Symbol.is_letter x) then "id" else "") ^ check_str xs

  end;

val mk_const_id = gen_mk_id Sign.constK I;

val mk_type_id = gen_mk_id Sign.typeK

  (fn s => if s mem ThmDatabase.ml_reserved then s ^ "_type" else s);

fun rename_term t =

  let

    val names = add_term_names (t, map (fst o fst o dest_Var) (term_vars t));

    val clash = names inter ThmDatabase.ml_reserved;

    val ps = clash ~~ variantlist (clash, names);

    fun rename (Var ((a, i), T)) = Var ((if_none (assoc (ps, a)) a, i), T)

      | rename (Free (a, T)) = Free (if_none (assoc (ps, a)) a, T)

      | rename (Abs (s, T, t)) = Abs (s, T, rename t)

      | rename (t $ u) = rename t $ rename u

      | rename t = t;

  in

    rename t

  end;

(**** invoke suitable code generator for term t ****)

fun invoke_codegen thy gr dep brack t = (case get_first

   (fn (_, f) => f thy gr dep brack t) (#codegens (CodegenData.get thy)) of

      None => error ("Unable to generate code for term:\n" ^

        Sign.string_of_term (sign_of thy) t ^ "\nrequired by:\n" ^

        commas (Graph.all_succs gr [dep]))

    | Some x => x)

(**** code generator for mixfix expressions ****)

fun parens p = Pretty.block [Pretty.str "(", p, Pretty.str ")"];

fun pretty_fn [] p = [p]

  | pretty_fn (x::xs) p = Pretty.str ("fn " ^ x ^ " =>") ::

      Pretty.brk 1 :: pretty_fn xs p;

fun pretty_mixfix [] [] _ = []

  | pretty_mixfix (Arg :: ms) (p :: ps) qs = p :: pretty_mixfix ms ps qs

  | pretty_mixfix (Ignore :: ms) (p :: ps) qs = pretty_mixfix ms ps qs

  | pretty_mixfix (Pretty p :: ms) ps qs = p :: pretty_mixfix ms ps qs

  | pretty_mixfix (Term _ :: ms) ps (q :: qs) = q :: pretty_mixfix ms ps qs;

(**** default code generator ****)

fun eta_expand t ts i =

  let

    val (Ts, _) = strip_type (fastype_of t);

    val j = i - length ts

  in

    foldr (fn (T, t) => Abs ("x", T, t))

      (take (j, Ts), list_comb (t, ts @ map Bound (j-1 downto 0)))

  end;

fun mk_app _ p [] = p

  | mk_app brack p ps = if brack then

       Pretty.block (Pretty.str "(" ::

         separate (Pretty.brk 1) (p :: ps) @ [Pretty.str ")"])

     else Pretty.block (separate (Pretty.brk 1) (p :: ps));

fun new_names t xs = variantlist (xs,

  map (fst o fst o dest_Var) (term_vars t) union

  add_term_names (t, ThmDatabase.ml_reserved));

fun new_name t x = hd (new_names t [x]);

fun default_codegen thy gr dep brack t =

  let

    val (u, ts) = strip_comb t;

    fun mapcode brack' gr ts = foldl_map

      (fn (gr, t) => invoke_codegen thy gr dep brack' t) (gr, ts)

  in (case u of

      Var ((s, i), _) =>

        let val (gr', ps) = mapcode true gr ts

        in Some (gr', mk_app brack (Pretty.str (s ^

           (if i=0 then "" else string_of_int i))) ps)

        end

    | Free (s, _) =>

        let val (gr', ps) = mapcode true gr ts

        in Some (gr', mk_app brack (Pretty.str s) ps) end

    | Const (s, T) =>

      (case get_assoc_code thy s T of

         Some ms =>

           let val i = num_args ms

           in if length ts < i then

               default_codegen thy gr dep brack (eta_expand u ts i)

             else

               let

                 val ts1 = take (i, ts);

                 val ts2 = drop (i, ts);

                 val (gr1, ps1) = mapcode false gr ts1;

                 val (gr2, ps2) = mapcode true gr1 ts2;

                 val (gr3, ps3) = mapcode false gr2 (terms_of ms);

               in

                 Some (gr3, mk_app brack (Pretty.block (pretty_mixfix ms ps1 ps3)) ps2)

               end

           end

       | None => (case get_defn thy s T of

           None => None

         | Some ((args, rhs), k) =>

             let

               val id = mk_const_id (sign_of thy) s ^ (case k of

                 None => "" | Some i => "_def" ^ string_of_int i);

               val (gr', ps) = mapcode true gr ts;

             in

               Some (Graph.add_edge (id, dep) gr' handle Graph.UNDEF _ =>

                 let

                   val _ = message ("expanding definition of " ^ s);

                   val (Ts, _) = strip_type T;

                   val (args', rhs') =

                     if not (null args) orelse null Ts then (args, rhs) else

                       let val v = Free (new_name rhs "x", hd Ts)

                       in ([v], betapply (rhs, v)) end;

                   val (gr1, p) = invoke_codegen thy (Graph.add_edge (id, dep)

                     (Graph.new_node (id, (None, "")) gr')) id false rhs';

                   val (gr2, xs) = mapcode false gr1 args';

                 in Graph.map_node id (K (None, Pretty.string_of (Pretty.block

                   (Pretty.str (if null args' then "val " else "fun ") ::

                    separate (Pretty.brk 1) (Pretty.str id :: xs) @

                    [Pretty.str " =", Pretty.brk 1, p, Pretty.str ";"])) ^ "\n\n")) gr2

                 end, mk_app brack (Pretty.str id) ps)

             end))

    | Abs _ =>

      let

        val (bs, Ts) = ListPair.unzip (strip_abs_vars u);

        val t = strip_abs_body u

        val bs' = new_names t bs;

        val (gr1, ps) = mapcode true gr ts;

        val (gr2, p) = invoke_codegen thy gr1 dep false

          (subst_bounds (map Free (rev (bs' ~~ Ts)), t));

      in

        Some (gr2, mk_app brack (Pretty.block (Pretty.str "(" :: pretty_fn bs' p @

          [Pretty.str ")"])) ps)

      end

    | _ => None)

  end;

fun output_code gr xs = implode (map (snd o Graph.get_node gr)

  (rev (Graph.all_preds gr xs)));

fun gen_generate_code prep_term thy = Pretty.setmp_margin 80 (fn xs =>

  let

    val sg = sign_of thy;

    val gr = Graph.new_node ("<Top>", (None, "")) Graph.empty;

    val (gr', ps) = foldl_map (fn (gr, (s, t)) => apsnd (pair s)

      (invoke_codegen thy gr "<Top>" false t)) (gr, map (apsnd (prep_term sg)) xs)

  in

    "structure Generated =\nstruct\n\n" ^

    output_code gr' ["<Top>"] ^

    space_implode "\n\n" (map (fn (s', p) => Pretty.string_of (Pretty.block

      [Pretty.str ("val " ^ s' ^ " ="), Pretty.brk 1, p, Pretty.str ";"])) ps) ^

    "\n\nend;\n\nopen Generated;\n"

  end);

val generate_code_i = gen_generate_code (K I);

val generate_code = gen_generate_code

  (fn sg => term_of o read_cterm sg o rpair TypeInfer.logicT);

fun parse_mixfix rd s =

  (case Scan.finite Symbol.stopper (Scan.repeat

     (   $$ "_" >> K Arg

      || $$ "?" >> K Ignore

      || $$ "/" |-- Scan.repeat ($$ " ") >> (Pretty o Pretty.brk o length)

      || $$ "{" |-- $$ "*" |-- Scan.repeat1

           (   $$ "'" |-- Scan.one Symbol.not_eof

            || Scan.unless ($$ "*" -- $$ "}") (Scan.one Symbol.not_eof)) --|

         $$ "*" --| $$ "}" >> (Term o rd o implode)

      || Scan.repeat1

           (   $$ "'" |-- Scan.one Symbol.not_eof

            || Scan.unless ($$ "_" || $$ "?" || $$ "/" || $$ "{" |-- $$ "*")

                 (Scan.one Symbol.not_eof)) >> (Pretty o Pretty.str o implode)))

       (Symbol.explode s) of

     (p, []) => p

   | _ => error ("Malformed annotation: " ^ quote s));

structure P = OuterParse and K = OuterSyntax.Keyword;

val assoc_typeP =

  OuterSyntax.command "types_code"

  "associate types with target language types" K.thy_decl

    (Scan.repeat1 (P.xname --| P.$$$ "(" -- P.string --| P.$$$ ")") >>

     (Toplevel.theory o assoc_types));

val assoc_constP =

  OuterSyntax.command "consts_code"

  "associate constants with target language code" K.thy_decl

    (Scan.repeat1

       (P.xname -- (Scan.option (P.$$$ "::" |-- P.string)) --|

        P.$$$ "(" -- P.string --| P.$$$ ")") >>

     (fn xs => Toplevel.theory (fn thy => assoc_consts

       (map (fn ((name, optype), mfx) => (name, optype, parse_mixfix

         (term_of o read_cterm (sign_of thy) o rpair TypeInfer.logicT) mfx))

           xs) thy)));

val generate_codeP =

  OuterSyntax.command "generate_code" "generates code for terms" K.thy_decl

    (Scan.option (P.$$$ "(" |-- P.string --| P.$$$ ")") --

     Scan.repeat1 (P.name --| P.$$$ "=" -- P.string) >>

     (fn (opt_fname, xs) => Toplevel.theory (fn thy =>

        ((case opt_fname of

            None => use_text Context.ml_output false

          | Some fname => File.write (Path.unpack fname))

              (generate_code thy xs); thy))));

val parsers = [assoc_typeP, assoc_constP, generate_codeP];

val setup = [CodegenData.init, add_codegen "default" default_codegen];

end;

OuterSyntax.add_parsers Codegen.parsers;