src/Pure/name.ML
author wenzelm
Mon Mar 10 15:04:01 2014 +0100 (2014-03-10)
changeset 56026 893fe12639bc
parent 55949 4766342e8376
child 56811 b66639331db5
permissions -rw-r--r--
tuned signature -- prefer Name_Space.get with its builtin error;
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(*  Title:      Pure/name.ML
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    Author:     Makarius
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Names of basic logical entities (variables etc.).
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*)
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signature NAME =
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sig
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  val uu: string
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  val uu_: string
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  val aT: string
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  val bound: int -> string
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  val is_bound: string -> bool
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  val internal: string -> string
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  val dest_internal: string -> string
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  val is_internal: string -> bool
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  val reject_internal: string * Position.T list -> unit
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  val skolem: string -> string
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  val dest_skolem: string -> string
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  val is_skolem: string -> bool
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  val reject_skolem: string * Position.T list -> unit
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  val clean_index: string * int -> string * int
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  val clean: string -> string
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  type context
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  val context: context
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  val make_context: string list -> context
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  val declare: string -> context -> context
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  val is_declared: context -> string -> bool
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  val invent: context -> string -> int -> string list
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  val invent_names: context -> string -> 'a list -> (string * 'a) list
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  val invent_list: string list -> string -> int -> string list
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  val variant: string -> context -> string * context
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  val variant_list: string list -> string list -> string list
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  val desymbolize: bool -> string -> string
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end;
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structure Name: NAME =
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struct
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(** common defaults **)
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val uu = "uu";
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val uu_ = "uu_";
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val aT = "'a";
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(** special variable names **)
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(* encoded bounds *)
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(*names for numbered variables --
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  preserves order wrt. int_ord vs. string_ord, avoids allocating new strings*)
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val small_int = Vector.tabulate (1000, fn i =>
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  let val leading = if i < 10 then "00" else if i < 100 then "0" else ""
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  in ":" ^ leading ^ string_of_int i end);
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fun bound n =
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  if n < 1000 then Vector.sub (small_int, n)
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  else ":" ^ bound (n div 1000) ^ Vector.sub (small_int, n mod 1000);
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val is_bound = String.isPrefix ":";
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(* internal names -- NB: internal subsumes skolem *)
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val internal = suffix "_";
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val dest_internal = unsuffix "_";
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val is_internal = String.isSuffix "_";
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fun reject_internal (x, ps) =
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  if is_internal x then error ("Bad name: " ^ quote x ^ Position.here_list ps) else ();
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val skolem = suffix "__";
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val dest_skolem = unsuffix "__";
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val is_skolem = String.isSuffix "__";
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fun reject_skolem (x, ps) =
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  if is_skolem x then error ("Bad name: " ^ quote x ^ Position.here_list ps) else ();
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fun clean_index (x, i) =
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  (case try dest_internal x of
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    NONE => (x, i)
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  | SOME x' => clean_index (x', i + 1));
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fun clean x = #1 (clean_index (x, 0));
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(** generating fresh names **)
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(* context *)
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datatype context =
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  Context of string option Symtab.table;    (*declared names with latest renaming*)
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fun declare x (Context tab) =
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  Context (Symtab.default (clean x, NONE) tab);
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fun declare_renaming (x, x') (Context tab) =
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  Context (Symtab.update (clean x, SOME (clean x')) tab);
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fun is_declared (Context tab) = Symtab.defined tab;
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fun declared (Context tab) = Symtab.lookup tab;
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val context = Context Symtab.empty |> fold declare ["", "'"];
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fun make_context used = fold declare used context;
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(* invent names *)
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fun invent ctxt =
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  let
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    fun invs _ 0 = []
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      | invs x n =
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          let val x' = Symbol.bump_string x
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          in if is_declared ctxt x then invs x' n else x :: invs x' (n - 1) end;
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  in invs o clean end;
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fun invent_names ctxt x xs = invent ctxt x (length xs) ~~ xs;
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val invent_list = invent o make_context;
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(* variants *)
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(*makes a variant of a name distinct from already used names in a
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  context; preserves a suffix of underscores "_"*)
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fun variant name ctxt =
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  let
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    fun vary x =
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      (case declared ctxt x of
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        NONE => x
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      | SOME x' => vary (Symbol.bump_string (the_default x x')));
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    val (x, n) = clean_index (name, 0);
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    val (x', ctxt') =
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      if not (is_declared ctxt x) then (x, declare x ctxt)
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      else
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        let
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          val x0 = Symbol.bump_init x;
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          val x' = vary x0;
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          val ctxt' = ctxt
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            |> x0 <> x' ? declare_renaming (x0, x')
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            |> declare x';
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        in (x', ctxt') end;
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  in (x' ^ replicate_string n "_", ctxt') end;
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fun variant_list used names = #1 (make_context used |> fold_map variant names);
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(* names conforming to typical requirements of identifiers in the world outside *)
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fun desymbolize upper "" = if upper then "X" else "x"
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  | desymbolize upper s =
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      let
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        val xs as (x :: _) = Symbol.explode s;
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        val ys =
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          if Symbol.is_ascii_letter x orelse Symbol.is_symbolic x then xs
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          else "x" :: xs;
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        fun is_valid x =
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          Symbol.is_ascii_letter x orelse Symbol.is_ascii_digit x;
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        fun sep [] = []
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          | sep (xs as "_" :: _) = xs
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          | sep xs = "_" :: xs;
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        fun desep ("_" :: xs) = xs
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          | desep xs = xs;
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        fun desymb x xs =
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          if is_valid x then x :: xs
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          else
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            (case Symbol.decode x of
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              Symbol.Sym name => "_" :: raw_explode name @ sep xs
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            | _ => sep xs);
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        fun upper_lower cs =
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          if upper then nth_map 0 Symbol.to_ascii_upper cs
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          else
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            (if forall Symbol.is_ascii_upper cs then map else nth_map 0)
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              Symbol.to_ascii_lower cs;
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      in fold_rev desymb ys [] |> desep |> upper_lower |> implode end;
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end;