(*  Title:      Tools/Code/code_haskell.ML

    Author:     Florian Haftmann, TU Muenchen

Serializer for Haskell.

*)

signature CODE_HASKELL =

sig

  val target: string

  val setup: theory -> theory

end;

structure Code_Haskell : CODE_HASKELL =

struct

val target = "Haskell";

open Basic_Code_Thingol;

open Code_Printer;

infixr 5 @@;

infixr 5 @|;

(** Haskell serializer **)

fun print_haskell_stmt labelled_name class_syntax tyco_syntax const_syntax

    reserved deresolve contr_classparam_typs deriving_show =

  let

    val deresolve_base = Long_Name.base_name o deresolve;

    fun class_name class = case class_syntax class

     of NONE => deresolve class

      | SOME class => class;

    fun print_typcontext tyvars vs = case maps (fn (v, sort) => map (pair v) sort) vs

     of [] => []

      | constraints => enum "," "(" ")" (

          map (fn (v, class) =>

            str (class_name class ^ " " ^ lookup_var tyvars v)) constraints)

          @@ str " => ";

    fun print_typforall tyvars vs = case map fst vs

     of [] => []

      | vnames => str "forall " :: Pretty.breaks

          (map (str o lookup_var tyvars) vnames) @ str "." @@ Pretty.brk 1;

    fun print_tyco_expr tyvars fxy (tyco, tys) =

      brackify fxy (str tyco :: map (print_typ tyvars BR) tys)

    and print_typ tyvars fxy (tycoexpr as tyco `%% tys) = (case tyco_syntax tyco

         of NONE => print_tyco_expr tyvars fxy (deresolve tyco, tys)

          | SOME (i, print) => print (print_typ tyvars) fxy tys)

      | print_typ tyvars fxy (ITyVar v) = (str o lookup_var tyvars) v;

    fun print_typdecl tyvars (vs, tycoexpr) =

      Pretty.block (print_typcontext tyvars vs @| print_tyco_expr tyvars NOBR tycoexpr);

    fun print_typscheme tyvars (vs, ty) =

      Pretty.block (print_typforall tyvars vs @ print_typcontext tyvars vs @| print_typ tyvars NOBR ty);

    fun print_term tyvars some_thm vars fxy (IConst c) =

          print_app tyvars some_thm vars fxy (c, [])

      | print_term tyvars some_thm vars fxy (t as (t1 `$ t2)) =

          (case Code_Thingol.unfold_const_app t

           of SOME app => print_app tyvars some_thm vars fxy app

            | _ =>

                brackify fxy [

                  print_term tyvars some_thm vars NOBR t1,

                  print_term tyvars some_thm vars BR t2

                ])

      | print_term tyvars some_thm vars fxy (IVar NONE) =

          str "_"

      | print_term tyvars some_thm vars fxy (IVar (SOME v)) =

          (str o lookup_var vars) v

      | print_term tyvars some_thm vars fxy (t as _ `|=> _) =

          let

            val (binds, t') = Code_Thingol.unfold_pat_abs t;

            val (ps, vars') = fold_map (print_bind tyvars some_thm BR o fst) binds vars;

          in brackets (str "\\" :: ps @ str "->" @@ print_term tyvars some_thm vars' NOBR t') end

      | print_term tyvars some_thm vars fxy (ICase (cases as (_, t0))) =

          (case Code_Thingol.unfold_const_app t0

           of SOME (c_ts as ((c, _), _)) => if is_none (const_syntax c)

                then print_case tyvars some_thm vars fxy cases

                else print_app tyvars some_thm vars fxy c_ts

            | NONE => print_case tyvars some_thm vars fxy cases)

    and print_app_expr tyvars some_thm vars ((c, (_, function_typs)), ts) = case contr_classparam_typs c

     of [] => (str o deresolve) c :: map (print_term tyvars some_thm vars BR) ts

      | fingerprint => let

          val ts_fingerprint = ts ~~ take (length ts) fingerprint;

          val needs_annotation = forall (fn (_, NONE) => true | (t, SOME _) =>

            (not o Code_Thingol.locally_monomorphic) t) ts_fingerprint;

          fun print_term_anno (t, NONE) _ = print_term tyvars some_thm vars BR t

            | print_term_anno (t, SOME _) ty =

                brackets [print_term tyvars some_thm vars NOBR t, str "::", print_typ tyvars NOBR ty];

        in

          if needs_annotation then

            (str o deresolve) c :: map2 print_term_anno ts_fingerprint (take (length ts) function_typs)

          else (str o deresolve) c :: map (print_term tyvars some_thm vars BR) ts

        end

    and print_app tyvars = gen_print_app (print_app_expr tyvars) (print_term tyvars) const_syntax

    and print_bind tyvars some_thm fxy p = gen_print_bind (print_term tyvars) some_thm fxy p

    and print_case tyvars some_thm vars fxy (cases as ((_, [_]), _)) =

          let

            val (binds, body) = Code_Thingol.unfold_let (ICase cases);

            fun print_match ((pat, ty), t) vars =

              vars

              |> print_bind tyvars some_thm BR pat

              |>> (fn p => semicolon [p, str "=", print_term tyvars some_thm vars NOBR t])

            val (ps, vars') = fold_map print_match binds vars;

          in brackify_block fxy (str "let {")

            ps

            (concat [str "}", str "in", print_term tyvars some_thm vars' NOBR body])

          end

      | print_case tyvars some_thm vars fxy (((t, ty), clauses as _ :: _), _) =

          let

            fun print_select (pat, body) =

              let

                val (p, vars') = print_bind tyvars some_thm NOBR pat vars;

              in semicolon [p, str "->", print_term tyvars some_thm vars' NOBR body] end;

          in Pretty.block_enclose

            (concat [str "(case", print_term tyvars some_thm vars NOBR t, str "of", str "{"], str "})")

            (map print_select clauses)

          end

      | print_case tyvars some_thm vars fxy ((_, []), _) =

          (brackify fxy o Pretty.breaks o map str) ["error", "\"empty case\""];

    fun print_stmt (name, Code_Thingol.Fun (_, (((vs, ty), raw_eqs), _))) =

          let

            val tyvars = intro_vars (map fst vs) reserved;

            fun print_err n =

              semicolon (

                (str o deresolve_base) name

                :: map str (replicate n "_")

                @ str "="

                :: str "error"

                @@ (str o ML_Syntax.print_string

                    o Long_Name.base_name o Long_Name.qualifier) name

              );

            fun print_eqn ((ts, t), (some_thm, _)) =

              let

                val consts = fold Code_Thingol.add_constnames (t :: ts) [];

                val vars = reserved

                  |> intro_base_names

                      (is_none o const_syntax) deresolve consts

                  |> intro_vars ((fold o Code_Thingol.fold_varnames)

                      (insert (op =)) ts []);

              in

                semicolon (

                  (str o deresolve_base) name

                  :: map (print_term tyvars some_thm vars BR) ts

                  @ str "="

                  @@ print_term tyvars some_thm vars NOBR t

                )

              end;

          in

            Pretty.chunks (

              semicolon [

                (str o suffix " ::" o deresolve_base) name,

                print_typscheme tyvars (vs, ty)

              ]

              :: (case filter (snd o snd) raw_eqs

               of [] => [print_err ((length o fst o Code_Thingol.unfold_fun) ty)]

                | eqs => map print_eqn eqs)

            )

          end

      | print_stmt (name, Code_Thingol.Datatype (_, (vs, []))) =

          let

            val tyvars = intro_vars (map fst vs) reserved;

          in

            semicolon [

              str "data",

              print_typdecl tyvars (vs, (deresolve_base name, map (ITyVar o fst) vs))

            ]

          end

      | print_stmt (name, Code_Thingol.Datatype (_, (vs, [((co, _), [ty])]))) =

          let

            val tyvars = intro_vars (map fst vs) reserved;

          in

            semicolon (

              str "newtype"

              :: print_typdecl tyvars (vs, (deresolve_base name, map (ITyVar o fst) vs))

              :: str "="

              :: (str o deresolve_base) co

              :: print_typ tyvars BR ty

              :: (if deriving_show name then [str "deriving (Read, Show)"] else [])

            )

          end

      | print_stmt (name, Code_Thingol.Datatype (_, (vs, co :: cos))) =

          let

            val tyvars = intro_vars (map fst vs) reserved;

            fun print_co ((co, _), tys) =

              concat (

                (str o deresolve_base) co

                :: map (print_typ tyvars BR) tys

              )

          in

            semicolon (

              str "data"

              :: print_typdecl tyvars (vs, (deresolve_base name, map (ITyVar o fst) vs))

              :: str "="

              :: print_co co

              :: map ((fn p => Pretty.block [str "| ", p]) o print_co) cos

              @ (if deriving_show name then [str "deriving (Read, Show)"] else [])

            )

          end

      | print_stmt (name, Code_Thingol.Class (_, (v, (super_classes, classparams)))) =

          let

            val tyvars = intro_vars [v] reserved;

            fun print_classparam (classparam, ty) =

              semicolon [

                (str o deresolve_base) classparam,

                str "::",

                print_typ tyvars NOBR ty

              ]

          in

            Pretty.block_enclose (

              Pretty.block [

                str "class ",

                Pretty.block (print_typcontext tyvars [(v, map fst super_classes)]),

                str (deresolve_base name ^ " " ^ lookup_var tyvars v),

                str " where {"

              ],

              str "};"

            ) (map print_classparam classparams)

          end

      | print_stmt (_, Code_Thingol.Classinst ((class, (tyco, vs)), (_, (classparam_instances, _)))) =

          let

            val tyvars = intro_vars (map fst vs) reserved;

            fun requires_args classparam = case const_syntax classparam

             of NONE => 0

              | SOME (Code_Printer.Plain_const_syntax _) => 0

              | SOME (Code_Printer.Complex_const_syntax (k,_ )) => k;

            fun print_classparam_instance ((classparam, const), (thm, _)) =

              case requires_args classparam

               of 0 => semicolon [

                      (str o deresolve_base) classparam,

                      str "=",

                      print_app tyvars (SOME thm) reserved NOBR (const, [])

                    ]

                | k =>

                    let

                      val (c, (_, tys)) = const;

                      val (vs, rhs) = (apfst o map) fst

                        (Code_Thingol.unfold_abs (Code_Thingol.eta_expand k (const, [])));

                      val s = if (is_some o const_syntax) c

                        then NONE else (SOME o Long_Name.base_name o deresolve) c;

                      val vars = reserved

                        |> intro_vars (map_filter I (s :: vs));

                      val lhs = IConst (classparam, (([], []), tys)) `$$ map IVar vs;

                        (*dictionaries are not relevant at this late stage*)

                    in

                      semicolon [

                        print_term tyvars (SOME thm) vars NOBR lhs,

                        str "=",

                        print_term tyvars (SOME thm) vars NOBR rhs

                      ]

                    end;

          in

            Pretty.block_enclose (

              Pretty.block [

                str "instance ",

                Pretty.block (print_typcontext tyvars vs),

                str (class_name class ^ " "),

                print_typ tyvars BR (tyco `%% map (ITyVar o fst) vs),

                str " where {"

              ],

              str "};"

            ) (map print_classparam_instance classparam_instances)

          end;

  in print_stmt end;

type flat_program = ((string * Code_Thingol.stmt) Graph.T * ((string * (string list * string list)) list)) Graph.T;

fun flat_program labelled_name { module_alias, module_prefix, reserved,

      empty_nsp, namify_stmt, modify_stmt } program =

  let

    (* building module name hierarchy *)

    val fragments_tab = Code_Namespace.build_module_namespace { module_alias = module_alias,

      module_prefix = module_prefix, reserved = reserved } program;

    val dest_name = Code_Namespace.dest_name

      #>> (Long_Name.implode o the o Symtab.lookup fragments_tab);

    (* distribute statements over hierarchy *)

    fun add_stmt name stmt =

      let

        val (module_name, base) = dest_name name;

      in case modify_stmt stmt

       of SOME stmt' => 

            Graph.default_node (module_name, (Graph.empty, []))

            #> (Graph.map_node module_name o apfst) (Graph.new_node (name, (base, stmt')))

        | NONE => I

      end;

    fun add_dependency name name' =

      let

        val (module_name, base) = dest_name name;

        val (module_name', base') = dest_name name';

      in if module_name = module_name'

        then (Graph.map_node module_name o apfst) (Graph.add_edge (name, name'))

        else (Graph.map_node module_name o apsnd)

          (AList.map_default (op =) (module_name', []) (insert (op =) name'))

      end;

    val proto_program = Graph.empty

      |> Graph.fold (fn (name, (stmt, _)) => add_stmt name stmt) program

      |> Graph.fold (fn (name, (_, (_, names))) => fold (add_dependency name) names) program;

    (* name declarations *)

    fun declare name (base, stmt) (gr, nsp) = 

      let

        val (base', nsp') = namify_stmt stmt base nsp;

        val gr' = (Graph.map_node name o apfst) (K base') gr;

      in (gr', nsp') end;

    fun declarations gr = (gr, empty_nsp)

      |> fold (fn name => declare name (Graph.get_node gr name)) (Graph.keys gr) 

      |> fst;

    val intermediate_program = proto_program

      |> Graph.map ((K o apfst) declarations);

    (* qualified and unqualified imports, deresolving *)

    fun base_deresolver name = fst (Graph.get_node

      (fst (Graph.get_node intermediate_program (fst (dest_name name)))) name);

    fun classify_imports gr imports =

      let

        val import_tab = maps

          (fn (module_name, names) => map (rpair module_name) names) imports;

        val imported_names = map fst import_tab;

        val here_names = Graph.keys gr;

        val qualified_names = []

          |> fold (fn name => AList.map_default (op =) (base_deresolver name, [])

               (insert (op =) name)) (here_names @ imported_names)

          |> filter (fn (_, names) => length names > 1)

          |> maps snd;

        val name_tab = Symtab.empty

          |> fold (fn name => Symtab.update (name, base_deresolver name)) here_names

          |> fold (fn name => Symtab.update (name,

               if member (op =) qualified_names name

               then Long_Name.append (the (AList.lookup (op =) import_tab name))

                 (base_deresolver name)

               else base_deresolver name)) imported_names;

        val imports' = (map o apsnd) (List.partition (member (op =) qualified_names))

          imports;

      in (name_tab, imports') end;

    val classified = AList.make (uncurry classify_imports o Graph.get_node intermediate_program)

      (Graph.keys intermediate_program);

    val flat_program = Graph.map (apsnd o K o snd o the o AList.lookup (op =) classified)

      intermediate_program;

    val deresolver_tab = Symtab.empty

      |> fold (fn (module_name, (name_tab, _)) => Symtab.update (module_name, name_tab)) classified;

    fun deresolver module_name name =

      the (Symtab.lookup (the (Symtab.lookup deresolver_tab module_name)) name)

      handle Option => error ("Unknown statement name: " ^ labelled_name name);

  in (deresolver, flat_program) end;

fun haskell_program_of_program labelled_name module_alias module_prefix reserved =

  let

    fun namify_fun upper base (nsp_fun, nsp_typ) =

      let

        val (base', nsp_fun') = yield_singleton Name.variants

          (if upper then first_upper base else base) nsp_fun;

      in (base', (nsp_fun', nsp_typ)) end;

    fun namify_typ base (nsp_fun, nsp_typ) =

      let

        val (base', nsp_typ') = yield_singleton Name.variants

          (first_upper base) nsp_typ

      in (base', (nsp_fun, nsp_typ')) end;

    fun namify_stmt (Code_Thingol.Fun (_, (_, SOME _))) = pair

      | namify_stmt (Code_Thingol.Fun _) = namify_fun false

      | namify_stmt (Code_Thingol.Datatype _) = namify_typ

      | namify_stmt (Code_Thingol.Datatypecons _) = namify_fun true

      | namify_stmt (Code_Thingol.Class _) = namify_typ

      | namify_stmt (Code_Thingol.Classrel _) = pair

      | namify_stmt (Code_Thingol.Classparam _) = namify_fun false

      | namify_stmt (Code_Thingol.Classinst _) = pair;

    fun select_stmt (Code_Thingol.Fun (_, (_, SOME _))) = false

      | select_stmt (Code_Thingol.Fun _) = true

      | select_stmt (Code_Thingol.Datatype _) = true

      | select_stmt (Code_Thingol.Datatypecons _) = false

      | select_stmt (Code_Thingol.Class _) = true

      | select_stmt (Code_Thingol.Classrel _) = false

      | select_stmt (Code_Thingol.Classparam _) = false

      | select_stmt (Code_Thingol.Classinst _) = true;

  in

    flat_program labelled_name

      { module_alias = module_alias, module_prefix = module_prefix,

        reserved = reserved, empty_nsp = (reserved, reserved), namify_stmt = namify_stmt,

        modify_stmt = fn stmt => if select_stmt stmt then SOME stmt else NONE }

  end;

fun mk_name_module reserved module_prefix module_alias program =

  let

    val fragments_tab = Code_Namespace.build_module_namespace { module_alias = module_alias,

      module_prefix = module_prefix, reserved = reserved } program;

  in Long_Name.implode o the o Symtab.lookup fragments_tab end;

fun haskell_program_of_program labelled_name module_prefix reserved module_alias program =

  let

    val reserved = Name.make_context reserved;

    val mk_name_module = mk_name_module reserved module_prefix module_alias program;

    fun add_stmt (name, (stmt, deps)) =

      let

        val (module_name, base) = Code_Namespace.dest_name name;

        val module_name' = mk_name_module module_name;

        val mk_name_stmt = yield_singleton Name.variants;

        fun add_fun upper (nsp_fun, nsp_typ) =

          let

            val (base', nsp_fun') =

              mk_name_stmt (if upper then first_upper base else base) nsp_fun

          in (base', (nsp_fun', nsp_typ)) end;

        fun add_typ (nsp_fun, nsp_typ) =

          let

            val (base', nsp_typ') = mk_name_stmt (first_upper base) nsp_typ

          in (base', (nsp_fun, nsp_typ')) end;

        val add_name = case stmt

         of Code_Thingol.Fun (_, (_, SOME _)) => pair base

          | Code_Thingol.Fun _ => add_fun false

          | Code_Thingol.Datatype _ => add_typ

          | Code_Thingol.Datatypecons _ => add_fun true

          | Code_Thingol.Class _ => add_typ

          | Code_Thingol.Classrel _ => pair base

          | Code_Thingol.Classparam _ => add_fun false

          | Code_Thingol.Classinst _ => pair base;

        fun add_stmt' base' = case stmt

         of Code_Thingol.Fun (_, (_, SOME _)) =>

              I

          | Code_Thingol.Datatypecons _ =>

              cons (name, (Long_Name.append module_name' base', NONE))

          | Code_Thingol.Classrel _ => I

          | Code_Thingol.Classparam _ =>

              cons (name, (Long_Name.append module_name' base', NONE))

          | _ => cons (name, (Long_Name.append module_name' base', SOME stmt));

      in

        Symtab.map_default (module_name', ([], ([], (reserved, reserved))))

              (apfst (fold (insert (op = : string * string -> bool)) deps))

        #> `(fn program => add_name ((snd o snd o the o Symtab.lookup program) module_name'))

        #-> (fn (base', names) =>

              (Symtab.map_entry module_name' o apsnd) (fn (stmts, _) =>

              (add_stmt' base' stmts, names)))

      end;

    val hs_program = fold add_stmt (AList.make (fn name =>

      (Graph.get_node program name, Graph.imm_succs program name))

      (Graph.strong_conn program |> flat)) Symtab.empty;

    fun deresolver name = (fst o the o AList.lookup (op =) ((fst o snd o the

      o Symtab.lookup hs_program) ((mk_name_module o fst o Code_Namespace.dest_name) name))) name

      handle Option => error ("Unknown statement name: " ^ labelled_name name);

  in (deresolver, hs_program) end;

fun serialize_haskell module_prefix string_classes { labelled_name, reserved_syms,

    includes, module_alias, class_syntax, tyco_syntax, const_syntax, program } =

  let

    val reserved = fold (insert (op =) o fst) includes reserved_syms;

    val (deresolver, hs_program) = haskell_program_of_program labelled_name

      module_prefix reserved module_alias program;

    val contr_classparam_typs = Code_Thingol.contr_classparam_typs program;

    fun deriving_show tyco =

      let

        fun deriv _ "fun" = false

          | deriv tycos tyco = not (tyco = Code_Thingol.fun_tyco)

              andalso (member (op =) tycos tyco

              orelse case try (Graph.get_node program) tyco

                of SOME (Code_Thingol.Datatype (_, (_, cs))) => forall (deriv' (tyco :: tycos))

                    (maps snd cs)

                 | NONE => true)

        and deriv' tycos (tyco `%% tys) = deriv tycos tyco

              andalso forall (deriv' tycos) tys

          | deriv' _ (ITyVar _) = true

      in deriv [] tyco end;

    val reserved = make_vars reserved;

    fun print_stmt qualified = print_haskell_stmt labelled_name

      class_syntax tyco_syntax const_syntax reserved

      (if qualified then deresolver else Long_Name.base_name o deresolver)

      contr_classparam_typs

      (if string_classes then deriving_show else K false);

    fun print_module name content =

      (name, Pretty.chunks2 [

        str ("module " ^ name ^ " where {"),

        content,

        str "}"

      ]);

    fun serialize_module (module_name', (deps, (stmts, _))) =

      let

        val stmt_names = map fst stmts;

        val qualified = true;

        val imports = subtract (op =) stmt_names deps

          |> distinct (op =)

          |> map_filter (try deresolver)

          |> map Long_Name.qualifier

          |> distinct (op =);

        fun print_import_include (name, _) = str ("import qualified " ^ name ^ ";");

        fun print_import_module name = str ((if qualified

          then "import qualified "

          else "import ") ^ name ^ ";");

        val import_ps = map print_import_include includes @ map print_import_module imports

        val content = Pretty.chunks2 ((if null import_ps then [] else [Pretty.chunks import_ps])

            @ map_filter

              (fn (name, (_, SOME stmt)) => SOME (markup_stmt name (print_stmt qualified (name, stmt)))

                | (_, (_, NONE)) => NONE) stmts

          );

      in print_module module_name' content end;

    fun write_module width (SOME destination) (modlname, content) =

          let

            val _ = File.check destination;

            val filename = case modlname

             of "" => Path.explode "Main.hs"

              | _ => (Path.ext "hs" o Path.explode o implode o separate "/"

                    o Long_Name.explode) modlname;

            val pathname = Path.append destination filename;

            val _ = File.mkdir_leaf (Path.dir pathname);

          in File.write pathname

            ("{-# OPTIONS_GHC -fglasgow-exts #-}\n\n"

              ^ format [] width content)

          end

      | write_module width NONE (_, content) = writeln (format [] width content);

  in

    Code_Target.serialization

      (fn width => fn destination => K () o map (write_module width destination))

      (fn present => fn width => rpair (fn _ => error "no deresolving") o format present width o Pretty.chunks o map snd)

      (map (uncurry print_module) includes

        @ map serialize_module (Symtab.dest hs_program))

  end;

val serializer : Code_Target.serializer =

  Code_Target.parse_args (Scan.option (Args.$$$ "root" -- Args.colon |-- Args.name)

    -- Scan.optional (Args.$$$ "string_classes" >> K true) false

    >> (fn (module_prefix, string_classes) =>

      serialize_haskell module_prefix string_classes));

val literals = let

  fun char_haskell c =

    let

      val s = ML_Syntax.print_char c;

    in if s = "'" then "\\'" else s end;

  fun numeral_haskell k = if k >= 0 then string_of_int k

    else Library.enclose "(" ")" (signed_string_of_int k);

in Literals {

  literal_char = Library.enclose "'" "'" o char_haskell,

  literal_string = quote o translate_string char_haskell,

  literal_numeral = numeral_haskell,

  literal_positive_numeral = numeral_haskell,

  literal_alternative_numeral = numeral_haskell,

  literal_naive_numeral = numeral_haskell,

  literal_list = enum "," "[" "]",

  infix_cons = (5, ":")

} end;

(** optional monad syntax **)

fun pretty_haskell_monad c_bind =

  let

    fun dest_bind t1 t2 = case Code_Thingol.split_pat_abs t2

     of SOME ((pat, ty), t') =>

          SOME ((SOME ((pat, ty), true), t1), t')

      | NONE => NONE;

    fun dest_monad c_bind_name (IConst (c, _) `$ t1 `$ t2) =

          if c = c_bind_name then dest_bind t1 t2

          else NONE

      | dest_monad _ t = case Code_Thingol.split_let t

         of SOME (((pat, ty), tbind), t') =>

              SOME ((SOME ((pat, ty), false), tbind), t')

          | NONE => NONE;

    fun implode_monad c_bind_name = Code_Thingol.unfoldr (dest_monad c_bind_name);

    fun print_monad print_bind print_term (NONE, t) vars =

          (semicolon [print_term vars NOBR t], vars)

      | print_monad print_bind print_term (SOME ((bind, _), true), t) vars = vars

          |> print_bind NOBR bind

          |>> (fn p => semicolon [p, str "<-", print_term vars NOBR t])

      | print_monad print_bind print_term (SOME ((bind, _), false), t) vars = vars

          |> print_bind NOBR bind

          |>> (fn p => semicolon [str "let", str "{", p, str "=", print_term vars NOBR t, str "}"]);

    fun pretty _ [c_bind'] print_term thm vars fxy [(t1, _), (t2, _)] = case dest_bind t1 t2

     of SOME (bind, t') => let

          val (binds, t'') = implode_monad c_bind' t'

          val (ps, vars') = fold_map (print_monad (gen_print_bind (K print_term) thm) print_term)

            (bind :: binds) vars;

        in

          (brackify fxy o single o enclose "do { " " }" o Pretty.breaks)

            (ps @| print_term vars' NOBR t'')

        end

      | NONE => brackify_infix (1, L) fxy

          (print_term vars (INFX (1, L)) t1, str ">>=", print_term vars (INFX (1, X)) t2)

  in (2, ([c_bind], pretty)) end;

fun add_monad target' raw_c_bind thy =

  let

    val c_bind = Code.read_const thy raw_c_bind;

  in if target = target' then

    thy

    |> Code_Target.add_const_syntax target c_bind

        (SOME (Code_Printer.complex_const_syntax (pretty_haskell_monad c_bind)))

  else error "Only Haskell target allows for monad syntax" end;

(** Isar setup **)

val _ =

  Outer_Syntax.command "code_monad" "define code syntax for monads" Keyword.thy_decl (

    Parse.term_group -- Parse.name >> (fn (raw_bind, target) =>

      Toplevel.theory  (add_monad target raw_bind))

  );

val setup =

  Code_Target.add_target

    (target, { serializer = serializer, literals = literals,

      check = { env_var = "EXEC_GHC", make_destination = I,

        make_command = fn ghc => fn module_name =>

          ghc ^ " -fglasgow-exts -odir build -hidir build -stubdir build -e \"\" " ^ module_name ^ ".hs" } })

  #> Code_Target.add_tyco_syntax target "fun" (SOME (2, fn print_typ => fn fxy => fn [ty1, ty2] =>

      brackify_infix (1, R) fxy (

        print_typ (INFX (1, X)) ty1,

        str "->",

        print_typ (INFX (1, R)) ty2

      )))

  #> fold (Code_Target.add_reserved target) [

      "hiding", "deriving", "where", "case", "of", "infix", "infixl", "infixr",

      "import", "default", "forall", "let", "in", "class", "qualified", "data",

      "newtype", "instance", "if", "then", "else", "type", "as", "do", "module"

    ]

  #> fold (Code_Target.add_reserved target) [

      "Prelude", "Main", "Bool", "Maybe", "Either", "Ordering", "Char", "String", "Int",

      "Integer", "Float", "Double", "Rational", "IO", "Eq", "Ord", "Enum", "Bounded",

      "Num", "Real", "Integral", "Fractional", "Floating", "RealFloat", "Monad", "Functor",

      "AlreadyExists", "ArithException", "ArrayException", "AssertionFailed", "AsyncException",

      "BlockedOnDeadMVar", "Deadlock", "Denormal", "DivideByZero", "DotNetException", "DynException",

      "Dynamic", "EOF", "EQ", "EmptyRec", "ErrorCall", "ExitException", "ExitFailure",

      "ExitSuccess", "False", "GT", "HeapOverflow",

      "IOError", "IOException", "IllegalOperation",

      "IndexOutOfBounds", "Just", "Key", "LT", "Left", "LossOfPrecision", "NoMethodError",

      "NoSuchThing", "NonTermination", "Nothing", "Obj", "OtherError", "Overflow",

      "PatternMatchFail", "PermissionDenied", "ProtocolError", "RecConError", "RecSelError",

      "RecUpdError", "ResourceBusy", "ResourceExhausted", "Right", "StackOverflow",

      "ThreadKilled", "True", "TyCon", "TypeRep", "UndefinedElement", "Underflow",

      "UnsupportedOperation", "UserError", "abs", "absReal", "acos", "acosh", "all",

      "and", "any", "appendFile", "asTypeOf", "asciiTab", "asin", "asinh", "atan",

      "atan2", "atanh", "basicIORun", "blockIO", "boundedEnumFrom", "boundedEnumFromThen",

      "boundedEnumFromThenTo", "boundedEnumFromTo", "boundedPred", "boundedSucc", "break",

      "catch", "catchException", "ceiling", "compare", "concat", "concatMap", "const",

      "cos", "cosh", "curry", "cycle", "decodeFloat", "denominator", "div", "divMod",

      "doubleToRatio", "doubleToRational", "drop", "dropWhile", "either", "elem",

      "emptyRec", "encodeFloat", "enumFrom", "enumFromThen", "enumFromThenTo",

      "enumFromTo", "error", "even", "exp", "exponent", "fail", "filter", "flip",

      "floatDigits", "floatProperFraction", "floatRadix", "floatRange", "floatToRational",

      "floor", "fmap", "foldl", "foldl'", "foldl1", "foldr", "foldr1", "fromDouble",

      "fromEnum", "fromEnum_0", "fromInt", "fromInteger", "fromIntegral", "fromObj",

      "fromRational", "fst", "gcd", "getChar", "getContents", "getLine", "head",

      "id", "inRange", "index", "init", "intToRatio", "interact", "ioError", "isAlpha",

      "isAlphaNum", "isDenormalized", "isDigit", "isHexDigit", "isIEEE", "isInfinite",

      "isLower", "isNaN", "isNegativeZero", "isOctDigit", "isSpace", "isUpper", "iterate", "iterate'",

      "last", "lcm", "length", "lex", "lexDigits", "lexLitChar", "lexmatch", "lines", "log",

      "logBase", "lookup", "loop", "map", "mapM", "mapM_", "max", "maxBound", "maximum",

      "maybe", "min", "minBound", "minimum", "mod", "negate", "nonnull", "not", "notElem",

      "null", "numerator", "numericEnumFrom", "numericEnumFromThen", "numericEnumFromThenTo",

      "numericEnumFromTo", "odd", "or", "otherwise", "pi", "pred", 

      "print", "product", "properFraction", "protectEsc", "putChar", "putStr", "putStrLn",

      "quot", "quotRem", "range", "rangeSize", "rationalToDouble", "rationalToFloat",

      "rationalToRealFloat", "read", "readDec", "readField", "readFieldName", "readFile",

      "readFloat", "readHex", "readIO", "readInt", "readList", "readLitChar", "readLn",

      "readOct", "readParen", "readSigned", "reads", "readsPrec", "realFloatToRational",

      "realToFrac", "recip", "reduce", "rem", "repeat", "replicate", "return", "reverse",

      "round", "scaleFloat", "scanl", "scanl1", "scanr", "scanr1", "seq", "sequence",

      "sequence_", "show", "showChar", "showException", "showField", "showList",

      "showLitChar", "showParen", "showString", "shows", "showsPrec", "significand",

      "signum", "signumReal", "sin", "sinh", "snd", "span", "splitAt", "sqrt", "subtract",

      "succ", "sum", "tail", "take", "takeWhile", "takeWhile1", "tan", "tanh", "threadToIOResult",

      "throw", "toEnum", "toInt", "toInteger", "toObj", "toRational", "truncate", "uncurry",

      "undefined", "unlines", "unsafeCoerce", "unsafeIndex", "unsafeRangeSize", "until", "unwords",

      "unzip", "unzip3", "userError", "words", "writeFile", "zip", "zip3", "zipWith", "zipWith3"

    ] (*due to weird handling of ':', we can't do anything else than to import *all* prelude symbols*);

end; (*struct*)