# HG changeset patch
# User wenzelm
# Date 910622012 -3600
# Node ID 77071ac7c7b526413efa263026102a7bc0280d20
# Parent  977f789566b7a388206c95b8822f2d6655c839ac
Histories of proof states, with undo / redo and prev / back.

diff -r 977f789566b7 -r 77071ac7c7b5 src/Pure/Isar/proof_history.ML
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/Isar/proof_history.ML	Mon Nov 09 15:33:32 1998 +0100
@@ -0,0 +1,105 @@
+(*  Title:      Pure/Isar/proof_history.ML
+    ID:         $Id$
+    Author:     Markus Wenzel, TU Muenchen
+
+Histories of proof states, with undo / redo and prev / back.
+*)
+
+signature PROOF_HISTORY =
+sig
+  type T
+  exception FAIL of string
+  val init: Proof.state -> T
+  val current: T -> Proof.state
+  val clear: T -> T
+  val undo: T -> T
+  val redo: T -> T
+  val position: T -> int
+  val nesting: T -> int
+  val prev: T -> T
+  val up: T -> T
+  val top: T -> T
+  val back: T -> T
+  val applys: (Proof.state -> Proof.state Seq.seq) -> T -> T
+  val applys_open: (Proof.state -> Proof.state Seq.seq) -> T -> T
+  val applys_close: (Proof.state -> Proof.state Seq.seq) -> T -> T
+  val apply: (Proof.state -> Proof.state) -> T -> T
+  val apply_open: (Proof.state -> Proof.state) -> T -> T
+  val apply_close: (Proof.state -> Proof.state) -> T -> T
+end;
+
+structure ProofHistory: PROOF_HISTORY =
+struct
+
+
+(* datatype proof history *)
+
+type node =
+ (Proof.state *			(*first result*)
+  Proof.state Seq.seq) *	(*alternative results*)
+  int;				(*nest level*)
+
+type proof = node * node list;
+
+datatype T = ProofHistory of proof History.T;
+
+exception FAIL of string;
+
+fun app f (ProofHistory x) = ProofHistory (f x);
+fun hist_app f = app (History.apply f);
+
+
+(* generic history operations *)
+
+fun init st = ProofHistory (History.init (((st, Seq.empty), 0), []));
+fun current (ProofHistory prf) = fst (fst (fst (History.current prf)));
+val clear = app History.clear;
+val undo = app History.undo;
+val redo = app History.redo;
+
+
+(* navigate *)
+
+fun position (ProofHistory prf) = length (snd (History.current prf));
+fun nesting (ProofHistory prf) = snd (fst (History.current prf));
+
+fun prev_until msg _ (_, []) = raise FAIL msg
+  | prev_until msg pred (_, node :: nodes) =
+      if pred node then (node, nodes)
+      else prev_until msg pred (node, nodes);
+
+val prev = hist_app (prev_until "no previous proof state" (K true));
+fun up prf = hist_app (prev_until "no upper proof state" (fn (_, m) => m < nesting prf)) prf;
+val top = hist_app (fn (node, nodes) => (last_elem (node :: nodes), []));
+
+
+(* backtrack *)
+
+fun back_fun (((_, stq), n), nodes) =
+  (case Seq.pull stq of
+    None =>
+      (case nodes of
+        [] => raise FAIL "back: no alternatives"
+      | nd :: nds => (writeln "back: trying previous proof state ..."; back_fun (nd, nds)))
+  | Some result => ((result, n), nodes));
+
+val back = hist_app back_fun;
+
+
+(* apply transformer *)
+
+fun gen_apply d f (node as ((st, _), n): node, nodes) =
+  (case Seq.pull (f st) of
+    None => raise FAIL "empty result sequence -- command failed"
+  | Some results => ((results, n + d), node :: nodes));
+
+val applys = hist_app o gen_apply 0;
+val applys_open = hist_app o gen_apply 1;
+val applys_close = hist_app o gen_apply ~1;
+
+fun apply f = applys (Seq.single o f);
+fun apply_open f = applys_open (Seq.single o f);
+fun apply_close f = applys_close (Seq.single o f);
+
+
+end;