(*  Title:      Tools/code/code_thingol.ML

    ID:         $Id$

    Author:     Florian Haftmann, TU Muenchen

Intermediate language ("Thin-gol") representing executable code.

Representation and translation.

*)

infix 8 `%%;

infixr 6 `->;

infixr 6 `-->;

infix 4 `$;

infix 4 `$$;

infixr 3 `|->;

infixr 3 `|-->;

signature BASIC_CODE_THINGOL =

sig

  type vname = string;

  datatype dict =

      DictConst of string * dict list list

    | DictVar of string list * (vname * (int * int));

  datatype itype =

      `%% of string * itype list

    | ITyVar of vname;

  type const = string * (dict list list * itype list (*types of arguments*))

  datatype iterm =

      IConst of const

    | IVar of vname

    | `$ of iterm * iterm

    | `|-> of (vname * itype) * iterm

    | ICase of ((iterm * itype) * (iterm * iterm) list) * iterm;

        (*((term, type), [(selector pattern, body term )]), primitive term)*)

  val `-> : itype * itype -> itype;

  val `--> : itype list * itype -> itype;

  val `$$ : iterm * iterm list -> iterm;

  val `|--> : (vname * itype) list * iterm -> iterm;

  type typscheme = (vname * sort) list * itype;

end;

signature CODE_THINGOL =

sig

  include BASIC_CODE_THINGOL;

  val unfoldl: ('a -> ('a * 'b) option) -> 'a -> 'a * 'b list;

  val unfoldr: ('a -> ('b * 'a) option) -> 'a -> 'b list * 'a;

  val unfold_fun: itype -> itype list * itype;

  val unfold_app: iterm -> iterm * iterm list;

  val split_abs: iterm -> (((vname * iterm option) * itype) * iterm) option;

  val unfold_abs: iterm -> ((vname * iterm option) * itype) list * iterm;

  val split_let: iterm -> (((iterm * itype) * iterm) * iterm) option;

  val unfold_let: iterm -> ((iterm * itype) * iterm) list * iterm;

  val unfold_const_app: iterm ->

    ((string * (dict list list * itype list)) * iterm list) option;

  val collapse_let: ((vname * itype) * iterm) * iterm

    -> (iterm * itype) * (iterm * iterm) list;

  val eta_expand: (string * (dict list list * itype list)) * iterm list -> int -> iterm;

  val contains_dictvar: iterm -> bool;

  val locally_monomorphic: iterm -> bool;

  val fold_constnames: (string -> 'a -> 'a) -> iterm -> 'a -> 'a;

  val fold_varnames: (string -> 'a -> 'a) -> iterm -> 'a -> 'a;

  val fold_unbound_varnames: (string -> 'a -> 'a) -> iterm -> 'a -> 'a;

  datatype stmt =

      Bot

    | Fun of typscheme * ((iterm list * iterm) * thm) list

    | Datatype of (vname * sort) list * (string * itype list) list

    | Datatypecons of string

    | Class of vname * ((class * string) list * (string * itype) list)

    | Classrel of class * class

    | Classparam of class

    | Classinst of (class * (string * (vname * sort) list))

          * ((class * (string * (string * dict list list))) list

        * ((string * const) * thm) list);

  type code = stmt Graph.T;

  val empty_code: code;

  val merge_code: code * code -> code;

  val project_code: bool (*delete empty funs*)

    -> string list (*hidden*) -> string list option (*selected*)

    -> code -> code;

  val empty_funs: code -> string list;

  val is_cons: code -> string -> bool;

  val contr_classparam_typs: code -> string -> itype option list;

  type transact;

  val ensure_const: theory -> ((sort -> sort) * Sorts.algebra) * Consts.T

    -> CodeFuncgr.T -> string -> transact -> string * transact;

  val ensure_value: theory -> ((sort -> sort) * Sorts.algebra) * Consts.T

    -> CodeFuncgr.T -> term

      -> transact -> (code * ((typscheme * iterm) * string list)) * transact;

  val transact: theory -> CodeFuncgr.T

    -> (theory -> ((sort -> sort) * Sorts.algebra) * Consts.T -> CodeFuncgr.T

      -> transact -> 'a * transact) -> code -> 'a * code;

  val add_value_stmt: iterm * itype -> code -> code;

end;

structure CodeThingol: CODE_THINGOL =

struct

(** auxiliary **)

fun unfoldl dest x =

  case dest x

   of NONE => (x, [])

    | SOME (x1, x2) =>

        let val (x', xs') = unfoldl dest x1 in (x', xs' @ [x2]) end;

fun unfoldr dest x =

  case dest x

   of NONE => ([], x)

    | SOME (x1, x2) =>

        let val (xs', x') = unfoldr dest x2 in (x1::xs', x') end;

(** language core - types, pattern, expressions **)

(* language representation *)

type vname = string;

datatype dict =

    DictConst of string * dict list list

  | DictVar of string list * (vname * (int * int));

datatype itype =

    `%% of string * itype list

  | ITyVar of vname;

type const = string * (dict list list * itype list (*types of arguments*))

datatype iterm =

    IConst of const

  | IVar of vname

  | `$ of iterm * iterm

  | `|-> of (vname * itype) * iterm

  | ICase of ((iterm * itype) * (iterm * iterm) list) * iterm;

    (*see also signature*)

(*

  variable naming conventions

  bare names:

    variable names          v

    class names             class

    type constructor names  tyco

    datatype names          dtco

    const names (general)   c (const)

    constructor names       co

    class parameter names   classparam

    arbitrary name          s

    v, c, co, classparam also annotated with types etc.

  constructs:

    sort                    sort

    type parameters         vs

    type                    ty

    type schemes            tysm

    term                    t

    (term as pattern)       p

    instance (class, tyco)  inst

 *)

fun ty1 `-> ty2 = "fun" `%% [ty1, ty2];

val op `--> = Library.foldr (op `->);

val op `$$ = Library.foldl (op `$);

val op `|--> = Library.foldr (op `|->);

val unfold_fun = unfoldr

  (fn "fun" `%% [ty1, ty2] => SOME (ty1, ty2)

    | _ => NONE);

val unfold_app = unfoldl

  (fn op `$ t => SOME t

    | _ => NONE);

val split_abs =

  (fn (v, ty) `|-> (t as ICase (((IVar w, _), [(p, t')]), _)) =>

        if v = w then SOME (((v, SOME p), ty), t') else SOME (((v, NONE), ty), t)

    | (v, ty) `|-> t => SOME (((v, NONE), ty), t)

    | _ => NONE);

val unfold_abs = unfoldr split_abs;

val split_let = 

  (fn ICase (((td, ty), [(p, t)]), _) => SOME (((p, ty), td), t)

    | _ => NONE);

val unfold_let = unfoldr split_let;

fun unfold_const_app t =

 case unfold_app t

  of (IConst c, ts) => SOME (c, ts)

   | _ => NONE;

fun fold_aiterms f (t as IConst _) = f t

  | fold_aiterms f (t as IVar _) = f t

  | fold_aiterms f (t1 `$ t2) = fold_aiterms f t1 #> fold_aiterms f t2

  | fold_aiterms f (t as _ `|-> t') = f t #> fold_aiterms f t'

  | fold_aiterms f (ICase (_, t)) = fold_aiterms f t;

fun fold_constnames f =

  let

    fun add (IConst (c, _)) = f c

      | add _ = I;

  in fold_aiterms add end;

fun fold_varnames f =

  let

    fun add (IVar v) = f v

      | add ((v, _) `|-> _) = f v

      | add _ = I;

  in fold_aiterms add end;

fun fold_unbound_varnames f =

  let

    fun add _ (IConst _) = I

      | add vs (IVar v) = if not (member (op =) vs v) then f v else I

      | add vs (t1 `$ t2) = add vs t1 #> add vs t2

      | add vs ((v, _) `|-> t) = add (insert (op =) v vs) t

      | add vs (ICase (_, t)) = add vs t;

  in add [] end;

fun collapse_let (((v, ty), se), be as ICase (((IVar w, _), ds), _)) =

      let

        fun exists_v t = fold_unbound_varnames (fn w => fn b =>

          b orelse v = w) t false;

      in if v = w andalso forall (fn (t1, t2) =>

        exists_v t1 orelse not (exists_v t2)) ds

        then ((se, ty), ds)

        else ((se, ty), [(IVar v, be)])

      end

  | collapse_let (((v, ty), se), be) =

      ((se, ty), [(IVar v, be)])

fun eta_expand (c as (_, (_, tys)), ts) k =

  let

    val j = length ts;

    val l = k - j;

    val ctxt = (fold o fold_varnames) Name.declare ts Name.context;

    val vs_tys = Name.names ctxt "a" ((curry Library.take l o curry Library.drop j) tys);

  in vs_tys `|--> IConst c `$$ ts @ map (fn (v, _) => IVar v) vs_tys end;

fun contains_dictvar t =

  let

    fun contains (DictConst (_, dss)) = (fold o fold) contains dss

      | contains (DictVar _) = K true;

  in

    fold_aiterms

      (fn IConst (_, (dss, _)) => (fold o fold) contains dss | _ => I) t false

  end;

fun locally_monomorphic (IConst _) = false

  | locally_monomorphic (IVar _) = true

  | locally_monomorphic (t `$ _) = locally_monomorphic t

  | locally_monomorphic (_ `|-> t) = locally_monomorphic t

  | locally_monomorphic (ICase ((_, ds), _)) = exists (locally_monomorphic o snd) ds;

(** definitions, transactions **)

type typscheme = (vname * sort) list * itype;

datatype stmt =

    Bot

  | Fun of typscheme * ((iterm list * iterm) * thm) list

  | Datatype of (vname * sort) list * (string * itype list) list

  | Datatypecons of string

  | Class of vname * ((class * string) list * (string * itype) list)

  | Classrel of class * class

  | Classparam of class

  | Classinst of (class * (string * (vname * sort) list))

        * ((class * (string * (string * dict list list))) list

      * ((string * const) * thm) list);

type code = stmt Graph.T;

(* abstract code *)

val empty_code = Graph.empty : code; (*read: "depends on"*)

fun ensure_bot name = Graph.default_node (name, Bot);

fun add_def_incr (name, Bot) code =

      (case the_default Bot (try (Graph.get_node code) name)

       of Bot => error "Attempted to add Bot to code"

        | _ => code)

  | add_def_incr (name, def) code =

      (case try (Graph.get_node code) name

       of NONE => Graph.new_node (name, def) code

        | SOME Bot => Graph.map_node name (K def) code

        | SOME _ => error ("Tried to overwrite definition " ^ quote name));

fun add_dep (NONE, _) = I

  | add_dep (SOME name1, name2) =

      if name1 = name2 then I else Graph.add_edge (name1, name2);

val merge_code : code * code -> code = Graph.merge (K true);

fun project_code delete_empty_funs hidden raw_selected code =

  let

    fun is_empty_fun name = case Graph.get_node code name

     of Fun (_, []) => true

      | _ => false;

    val names = subtract (op =) hidden (Graph.keys code);

    val deleted = Graph.all_preds code (filter is_empty_fun names);

    val selected = case raw_selected

     of NONE => names |> subtract (op =) deleted 

      | SOME sel => sel

          |> delete_empty_funs ? subtract (op =) deleted

          |> subtract (op =) hidden

          |> Graph.all_succs code

          |> delete_empty_funs ? subtract (op =) deleted

          |> subtract (op =) hidden;

  in

    code

    |> Graph.subgraph (member (op =) selected)

  end;

fun empty_funs code =

  Graph.fold (fn (name, (Fun (_, []), _)) => cons name

               | _ => I) code [];

fun is_cons code name = case Graph.get_node code name

 of Datatypecons _ => true

  | _ => false;

fun contr_classparam_typs code name = case Graph.get_node code name

 of Classparam class => let

        val Class (_, (_, params)) = Graph.get_node code class;

        val SOME ty = AList.lookup (op =) params name;

        val (tys, res_ty) = unfold_fun ty;

        fun no_tyvar (_ `%% tys) = forall no_tyvar tys

          | no_tyvar (ITyVar _) = false;

      in if no_tyvar res_ty

        then map (fn ty => if no_tyvar ty then NONE else SOME ty) tys

        else []

      end

  | _ => [];

(* transaction protocol *)

type transact = Graph.key option * code;

fun ensure_stmt stmtgen name (dep, code) =

  let

    fun add_def false =

          ensure_bot name

          #> add_dep (dep, name)

          #> curry stmtgen (SOME name)

          ##> snd

          #-> (fn def => add_def_incr (name, def))

      | add_def true =

          add_dep (dep, name);

  in

    code

    |> add_def (can (Graph.get_node code) name)

    |> pair dep

    |> pair name

  end;

fun transact thy funcgr f code =

  let

    val naming = NameSpace.qualified_names NameSpace.default_naming;

    val consttab = Consts.empty

      |> fold (fn c => Consts.declare true naming [] (c, CodeFuncgr.typ funcgr c))

           (CodeFuncgr.all funcgr);

    val algbr = (Code.operational_algebra thy, consttab);

  in

    (NONE, code)

    |> f thy algbr funcgr

    |-> (fn x => fn (_, code) => (x, code))

  end;

(* translation kernel *)

fun ensure_class thy (algbr as ((_, algebra), _)) funcgr class =

  let

    val superclasses = (Sorts.certify_sort algebra o Sorts.super_classes algebra) class;

    val cs = #params (AxClass.get_info thy class);

    val class' = CodeName.class thy class;

    val stmt_class =

      fold_map (fn superclass => ensure_class thy algbr funcgr superclass

        ##>> ensure_classrel thy algbr funcgr (class, superclass)) superclasses

      ##>> fold_map (fn (c, ty) => ensure_const thy algbr funcgr c

        ##>> exprgen_typ thy algbr funcgr ty) cs

      #>> (fn info => Class (unprefix "'" Name.aT, info))

  in

    ensure_stmt stmt_class class'

  end

and ensure_classrel thy algbr funcgr (subclass, superclass) =

  let

    val classrel' = CodeName.classrel thy (subclass, superclass);

    val stmt_classrel =

      ensure_class thy algbr funcgr subclass

      ##>> ensure_class thy algbr funcgr superclass

      #>> Classrel;

  in

    ensure_stmt stmt_classrel classrel'

  end

and ensure_tyco thy algbr funcgr "fun" =

      pair "fun"

  | ensure_tyco thy algbr funcgr tyco =

      let

        val stmt_datatype =

          let

            val (vs, cos) = Code.get_datatype thy tyco;

          in

            fold_map (exprgen_tyvar_sort thy algbr funcgr) vs

            ##>> fold_map (fn (c, tys) =>

              ensure_const thy algbr funcgr c

              ##>> fold_map (exprgen_typ thy algbr funcgr) tys) cos

            #>> Datatype

          end;

        val tyco' = CodeName.tyco thy tyco;

      in

        ensure_stmt stmt_datatype tyco'

      end

and exprgen_tyvar_sort thy (algbr as ((proj_sort, _), _)) funcgr (v, sort) =

  fold_map (ensure_class thy algbr funcgr) (proj_sort sort)

  #>> (fn sort => (unprefix "'" v, sort))

and exprgen_typ thy algbr funcgr (TFree vs) =

      exprgen_tyvar_sort thy algbr funcgr vs

      #>> (fn (v, sort) => ITyVar v)

  | exprgen_typ thy algbr funcgr (Type (tyco, tys)) =

      ensure_tyco thy algbr funcgr tyco

      ##>> fold_map (exprgen_typ thy algbr funcgr) tys

      #>> (fn (tyco, tys) => tyco `%% tys)

and exprgen_dicts thy (algbr as ((proj_sort, algebra), consts)) funcgr (ty_ctxt, sort_decl) =

  let

    val pp = Sign.pp thy;

    datatype typarg =

        Global of (class * string) * typarg list list

      | Local of (class * class) list * (string * (int * sort));

    fun class_relation (Global ((_, tyco), yss), _) class =

          Global ((class, tyco), yss)

      | class_relation (Local (classrels, v), subclass) superclass =

          Local ((subclass, superclass) :: classrels, v);

    fun type_constructor tyco yss class =

      Global ((class, tyco), (map o map) fst yss);

    fun type_variable (TFree (v, sort)) =

      let

        val sort' = proj_sort sort;

      in map_index (fn (n, class) => (Local ([], (v, (n, sort'))), class)) sort' end;

    val typargs = Sorts.of_sort_derivation pp algebra

      {class_relation = class_relation, type_constructor = type_constructor,

       type_variable = type_variable}

      (ty_ctxt, proj_sort sort_decl);

    fun mk_dict (Global (inst, yss)) =

          ensure_inst thy algbr funcgr inst

          ##>> (fold_map o fold_map) mk_dict yss

          #>> (fn (inst, dss) => DictConst (inst, dss))

      | mk_dict (Local (classrels, (v, (k, sort)))) =

          fold_map (ensure_classrel thy algbr funcgr) classrels

          #>> (fn classrels => DictVar (classrels, (unprefix "'" v, (k, length sort))))

  in

    fold_map mk_dict typargs

  end

and exprgen_dict_parms thy (algbr as (_, consts)) funcgr (c, ty_ctxt) =

  let

    val ty_decl = Consts.the_type consts c;

    val (tys, tys_decl) = pairself (curry (Consts.typargs consts) c) (ty_ctxt, ty_decl);

    val sorts = map (snd o dest_TVar) tys_decl;

  in

    fold_map (exprgen_dicts thy algbr funcgr) (tys ~~ sorts)

  end

and exprgen_eq thy algbr funcgr thm =

  let

    val (args, rhs) = (apfst (snd o strip_comb) o Logic.dest_equals

      o Logic.unvarify o prop_of) thm;

  in

    fold_map (exprgen_term thy algbr funcgr) args

    ##>> exprgen_term thy algbr funcgr rhs

    #>> rpair thm

  end

and ensure_inst thy (algbr as ((_, algebra), _)) funcgr (class, tyco) =

  let

    val superclasses = (Sorts.certify_sort algebra o Sorts.super_classes algebra) class;

    val classparams = these (try (#params o AxClass.get_info thy) class);

    val vs = Name.names Name.context "'a" (Sorts.mg_domain algebra tyco [class]);

    val sorts' = Sorts.mg_domain (Sign.classes_of thy) tyco [class];

    val vs' = map2 (fn (v, sort1) => fn sort2 => (v,

      Sorts.inter_sort (Sign.classes_of thy) (sort1, sort2))) vs sorts';

    val arity_typ = Type (tyco, map TFree vs);

    val arity_typ' = Type (tyco, map (fn (v, sort) => TVar ((v, 0), sort)) vs');

    fun exprgen_superarity superclass =

      ensure_class thy algbr funcgr superclass

      ##>> ensure_classrel thy algbr funcgr (class, superclass)

      ##>> exprgen_dicts thy algbr funcgr (arity_typ, [superclass])

      #>> (fn ((superclass, classrel), [DictConst (inst, dss)]) =>

            (superclass, (classrel, (inst, dss))));

    fun exprgen_classparam_inst (c, ty) =

      let

        val c_inst = Const (c, map_type_tfree (K arity_typ') ty);

        val thm = AxClass.unoverload_conv thy (Thm.cterm_of thy c_inst);

        val c_ty = (apsnd Logic.unvarifyT o dest_Const o snd

          o Logic.dest_equals o Thm.prop_of) thm;

      in

        ensure_const thy algbr funcgr c

        ##>> exprgen_const thy algbr funcgr c_ty

        #>> (fn (c, IConst c_inst) => ((c, c_inst), thm))

      end;

    val stmt_inst =

      ensure_class thy algbr funcgr class

      ##>> ensure_tyco thy algbr funcgr tyco

      ##>> fold_map (exprgen_tyvar_sort thy algbr funcgr) vs

      ##>> fold_map exprgen_superarity superclasses

      ##>> fold_map exprgen_classparam_inst classparams

      #>> (fn ((((class, tyco), arity), superarities), classparams) =>

             Classinst ((class, (tyco, arity)), (superarities, classparams)));

    val inst = CodeName.instance thy (class, tyco);

  in

    ensure_stmt stmt_inst inst

  end

and ensure_const thy (algbr as (_, consts)) funcgr c =

  let

    val c' = CodeName.const thy c;

    fun stmt_datatypecons tyco =

      ensure_tyco thy algbr funcgr tyco

      #>> Datatypecons;

    fun stmt_classparam class =

      ensure_class thy algbr funcgr class

      #>> Classparam;

    fun stmt_fun trns =

      let

        val raw_thms = CodeFuncgr.funcs funcgr c;

        val ty = (Logic.unvarifyT o CodeFuncgr.typ funcgr) c;

        val vs = (map dest_TFree o Consts.typargs consts) (c, ty);

        val thms = if (null o Term.typ_tfrees) ty orelse (null o fst o strip_type) ty

          then raw_thms

          else map (CodeUnit.expand_eta 1) raw_thms;

      in

        trns

        |> fold_map (exprgen_tyvar_sort thy algbr funcgr) vs

        ||>> exprgen_typ thy algbr funcgr ty

        ||>> fold_map (exprgen_eq thy algbr funcgr) thms

        |>> (fn ((vs, ty), eqs) => Fun ((vs, ty), eqs))

      end;

    val stmtgen = case Code.get_datatype_of_constr thy c

     of SOME tyco => stmt_datatypecons tyco

      | NONE => (case AxClass.class_of_param thy c

         of SOME class => stmt_classparam class

          | NONE => stmt_fun)

  in

    ensure_stmt stmtgen c'

  end

and exprgen_term thy algbr funcgr (Const (c, ty)) =

      exprgen_app thy algbr funcgr ((c, ty), [])

  | exprgen_term thy algbr funcgr (Free (v, _)) =

      pair (IVar v)

  | exprgen_term thy algbr funcgr (Abs (abs as (_, ty, _))) =

      let

        val (v, t) = Syntax.variant_abs abs;

      in

        exprgen_typ thy algbr funcgr ty

        ##>> exprgen_term thy algbr funcgr t

        #>> (fn (ty, t) => (v, ty) `|-> t)

      end

  | exprgen_term thy algbr funcgr (t as _ $ _) =

      case strip_comb t

       of (Const (c, ty), ts) =>

            exprgen_app thy algbr funcgr ((c, ty), ts)

        | (t', ts) =>

            exprgen_term thy algbr funcgr t'

            ##>> fold_map (exprgen_term thy algbr funcgr) ts

            #>> (fn (t, ts) => t `$$ ts)

and exprgen_const thy algbr funcgr (c, ty) =

  ensure_const thy algbr funcgr c

  ##>> exprgen_dict_parms thy algbr funcgr (c, ty)

  ##>> fold_map (exprgen_typ thy algbr funcgr) ((fst o Term.strip_type) ty)

  #>> (fn ((c, iss), tys) => IConst (c, (iss, tys)))

and exprgen_app_default thy algbr funcgr (c_ty, ts) =

  exprgen_const thy algbr funcgr c_ty

  ##>> fold_map (exprgen_term thy algbr funcgr) ts

  #>> (fn (t, ts) => t `$$ ts)

and exprgen_case thy algbr funcgr n cases (app as ((c, ty), ts)) =

  let

    val (tys, _) =

      (chop (1 + (if null cases then 1 else length cases)) o fst o strip_type) ty;

    val dt = nth ts n;

    val dty = nth tys n;

    fun is_undefined (Const (c, _)) = Code.is_undefined thy c

      | is_undefined _ = false;

    fun mk_case (co, n) t =

      let

        val (vs, body) = Term.strip_abs_eta n t;

        val selector = list_comb (Const (co, map snd vs ---> dty), map Free vs);

      in if is_undefined body then NONE else SOME (selector, body) end;

    fun mk_ds [] =

          let

            val ([v_ty], body) = Term.strip_abs_eta 1 (the_single (nth_drop n ts))

          in [(Free v_ty, body)] end

      | mk_ds cases = map_filter (uncurry mk_case)

          (AList.make (CodeUnit.no_args thy) cases ~~ nth_drop n ts);

  in

    exprgen_term thy algbr funcgr dt

    ##>> exprgen_typ thy algbr funcgr dty

    ##>> fold_map (fn (pat, body) => exprgen_term thy algbr funcgr pat

          ##>> exprgen_term thy algbr funcgr body) (mk_ds cases)

    ##>> exprgen_app_default thy algbr funcgr app

    #>> (fn (((dt, dty), ds), t0) => ICase (((dt, dty), ds), t0))

  end

and exprgen_app thy algbr funcgr ((c, ty), ts) = case Code.get_case_data thy c

 of SOME (n, cases) => let val i = 1 + (if null cases then 1 else length cases) in

      if length ts < i then

        let

          val k = length ts;

          val tys = (curry Library.take (i - k) o curry Library.drop k o fst o strip_type) ty;

          val ctxt = (fold o fold_aterms)

            (fn Free (v, _) => Name.declare v | _ => I) ts Name.context;

          val vs = Name.names ctxt "a" tys;

        in

          fold_map (exprgen_typ thy algbr funcgr) tys

          ##>> exprgen_case thy algbr funcgr n cases ((c, ty), ts @ map Free vs)

          #>> (fn (tys, t) => map2 (fn (v, _) => pair v) vs tys `|--> t)

        end

      else if length ts > i then

        exprgen_case thy algbr funcgr n cases ((c, ty), Library.take (i, ts))

        ##>> fold_map (exprgen_term thy algbr funcgr) (Library.drop (i, ts))

        #>> (fn (t, ts) => t `$$ ts)

      else

        exprgen_case thy algbr funcgr n cases ((c, ty), ts)

      end

  | NONE => exprgen_app_default thy algbr funcgr ((c, ty), ts);

(** evaluation **)

fun add_value_stmt (t, ty) code =

  code

  |> Graph.new_node (CodeName.value_name, Fun (([], ty), [(([], t), Drule.dummy_thm)]))

  |> fold (curry Graph.add_edge CodeName.value_name) (Graph.keys code);

fun ensure_value thy algbr funcgr t = 

  let

    val ty = fastype_of t;

    val vs = fold_term_types (K (fold_atyps (insert (eq_fst op =)

      o dest_TFree))) t [];

    val stmt_value =

      fold_map (exprgen_tyvar_sort thy algbr funcgr) vs

      ##>> exprgen_typ thy algbr funcgr ty

      ##>> exprgen_term thy algbr funcgr t

      #>> (fn ((vs, ty), t) => Fun ((vs, ty), [(([], t), Drule.dummy_thm)]));

    fun term_value (dep, code1) =

      let

        val Fun ((vs, ty), [(([], t), _)]) =

          Graph.get_node code1 CodeName.value_name;

        val deps = Graph.imm_succs code1 CodeName.value_name;

        val code2 = Graph.del_nodes [CodeName.value_name] code1;

        val code3 = project_code false [] (SOME deps) code2;

      in ((code3, (((vs, ty), t), deps)), (dep, code2)) end;

  in

    ensure_stmt stmt_value CodeName.value_name

    #> snd

    #> term_value

  end;

end; (*struct*)

structure BasicCodeThingol: BASIC_CODE_THINGOL = CodeThingol;