(* Title: Pure/Syntax/term_position.ML
Author: Makarius
Encoded position within term syntax trees.
*)
signature TERM_POSITION =
sig
val pretty: Position.T -> Pretty.T
val encode: Position.T -> string
val decode: string -> Position.T option
val decode_position: term -> (Position.T * typ) option
val decode_positionT: typ -> Position.T option
val decode_positionS: sort -> Position.T list * sort
val is_position: term -> bool
val is_positionT: typ -> bool
val markers: string list
val strip_positions: term -> term
end;
structure Term_Position: TERM_POSITION =
struct
(* markup *)
val position_dummy = "";
val position_text = XML.Text position_dummy;
fun pretty pos =
Pretty.markup (Position.markup pos Markup.position) [Pretty.str position_dummy];
fun encode pos =
YXML.string_of (XML.Elem (Position.markup pos Markup.position, [position_text]));
fun decode str =
(case YXML.parse_body str handle Fail msg => error msg of
[XML.Elem ((name, props), [arg])] =>
if name = Markup.positionN andalso arg = position_text
then SOME (Position.of_properties props)
else NONE
| _ => NONE);
(* positions within parse trees *)
fun decode_position (Free (x, _)) =
(case decode x of
SOME pos => SOME (pos, TFree (x, dummyS))
| NONE => NONE)
| decode_position _ = NONE;
fun decode_positionT (TFree (x, _)) = decode x
| decode_positionT _ = NONE;
fun decode_positionS cs =
let val (ps, sort) = List.partition (is_some o decode) cs
in (map (the o decode) ps, sort) end;
val is_position = is_some o decode_position;
val is_positionT = is_some o decode_positionT;
val markers = ["_constrain", "_constrainAbs", "_ofsort"];
fun strip_positions ((t as Const (c, _)) $ u $ v) =
if member (op =) markers c andalso is_position v
then strip_positions u
else t $ strip_positions u $ strip_positions v
| strip_positions (t $ u) = strip_positions t $ strip_positions u
| strip_positions (Abs (x, T, t)) = Abs (x, T, strip_positions t)
| strip_positions t = t;
end;
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