From 8de046df97b1ea391a3f3879c20c74d53c9fba48 Mon Sep 17 00:00:00 2001
From: Jim Fehrle
Date: Mon, 9 Apr 2018 13:16:46 -0700
Subject: Displays the differences between successive proof steps in coqtop and
 CoqIDE. Proof General requires minor changes to make the diffs visible, but
 this code shouldn't break the existing version of PG.

Diffs are computed for the hypotheses and conclusion of the first goal between
the old and new proofs. Strings are split into tokens using the Coq lexer,
then the list of tokens are diffed using the Myers algorithm.  A fixup routine
(Pp_diff.shorten_diff_span) shortens the span of the diff result in some cases.

Diffs can be enabled with the Coq commmand "Set Diffs on|off|removed." or
"-diffs on|off|removed" on the OS command line.  The "on" option shows only the
new item with added text, while "removed" shows each modified item twice--once
with the old value showing removed text and once with the new value showing
added text.

The highlights use 4 tags to specify the color and underline/strikeout.
These are "diffs.added", "diffs.removed", "diffs.added.bg" and "diffs.removed.bg".
The first two are for added or removed text; the last two are for
unmodified parts of a modified item.

Diffs that span multiple strings in the Pp are tagged with "start.diff.*" and
"end.diff.*", but only on the first and last strings of the span.
---
 lib/pp.mli | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'lib/pp.mli')

diff --git a/lib/pp.mli b/lib/pp.mli
index f3a0a29b8a..ed31daa561 100644
--- a/lib/pp.mli
+++ b/lib/pp.mli
@@ -189,3 +189,22 @@ val pr_vertical_list : ('b -> t) -> 'b list -> t
 val pp_with          : Format.formatter -> t -> unit
 
 val string_of_ppcmds : t -> string
+
+
+(** Tag prefix to start a multi-token diff span *)
+val start_pfx : string
+
+(** Tag prefix to end a multi-token diff span *)
+val end_pfx : string
+
+(** Split a tag into prefix and base tag *)
+val split_tag : string -> string * string
+
+(** Print the Pp in tree form for debugging *)
+val db_print_pp : Format.formatter -> t -> unit
+
+(** Print the Pp in tree form for debugging, return as a string *)
+val db_string_of_pp : t -> string
+
+(** Combine nested Ppcmd_glues *)
+val flatten : t -> t
-- 
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