This is a port of Bram Cohen's patience diff algorithm, as found in the Bazaar 1.14.1 source code, available at http://bazaar-vcs.org.

This copyright notice was included:

# Copyright (C) 2005 Bram Cohen, Copyright (C) 2005, 2006 Canonical Ltd # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

module Matching_block : sig .. end
Bram Cohen's comment from the original Python code (with syntax changed to OCaml):

get_matching_blocks a b returns a list of triples describing matching subsequences.

Each triple is of the form (i, j, n), and means that a <|> (i,i+n) = b <|> (j,j+n). The triples are monotonically increasing in i and in j.

The last triple is a dummy, (Array.length a, Array.length b, 0), and is the only triple with n=0.

Example: get_matching_blocks |"a";"b";"x";"c";"d"| |"a";"b";"c";"d"| returns (0, 0, 2), (3, 2, 2), (5, 4, 0)

type t = {
mine_start : int;
other_start : int;
length : int;
}
val get_matching_blocks : transform:('a -> 'b) ->
compare:('b -> 'b -> int) ->
mine:'a array -> other:'a array -> Matching_block.t list
val ratio : 'a array -> 'a array -> float
module Range : sig .. end
For handling diffs abstractly. A range is a subarray of the two original arrays with a constructor defining its relationship to the two original arrays. A Same range contains a series of elements which can be found in both arrays. A New range contains elements found only in the new array, while an Old range contains elements found only in the old array.

A Replace contains two arrays: elements in the first array are elements found only in the original, old array which have been replaced by elements in the second array, which are elements found only in the new array.

type 'a t = 
|Same of ('a * 'a) array
|Old of 'a array
|New of 'a array
|Replace of 'a array * 'a array
|Unified of 'a array
val all_same : 'a t list -> bool
val old_only : 'a t list -> 'a t list
old_only hunks drops all New ranges and converts all Replace ranges to Old ranges.
val new_only : 'a t list -> 'a t list
new_only hunks drops all Old ranges and converts all Replace ranges to New ranges.
val t_of_sexp : (Sexplib.Sexp.t -> 'a) -> Sexplib.Sexp.t -> 'a t
val sexp_of_t : ('a -> Sexplib.Sexp.t) -> 'a t -> Sexplib.Sexp.t
ranges_all_same ranges returns true if all ranges are Same
module Hunk : sig .. end
In diff terms, a hunk is a unit of consecutive ranges with some Same context before and after New, Old, and Replace ranges. Each hunk contains information about the original arrays, specifically the starting indexes and the number of elements in both arrays to which the hunk refers.

Furthermore, a diff is essentially a list of hunks. The simplest case is a diff with infinite context, consisting of exactly one hunk.

type 'a t = {
mine_start : int;
mine_size : int;
other_start : int;
other_size : int;
ranges : 'a Range.t list;
}
val all_same : 'a t -> bool
all_same hunk returns true if hunk contains only Same ranges.
val get_hunks : transform:('a -> 'b) ->
compare:('b -> 'b -> int) ->
context:int -> mine:'a array -> other:'a array -> 'a Hunk.t list
get_hunks a b ~context ~compare will compare the arrays a and b using compare and produce a list of hunks. (The hunks will contain Same ranges of at most context elements.) context defaults to infinity (producing a singleton hunk list), compare defaults to polymorphic compare.
val print_ranges : string Hunk.t -> unit
val all_same : 'a Hunk.t list -> bool
get_status hunks returns `Same if each hunk in hunks has only Same ranges.
val unified : 'a Hunk.t list -> 'a Hunk.t list
unified hunks converts all Replace ranges in hunks to an Old range followed by a New range.
val old_only : 'a Hunk.t list -> 'a Hunk.t list
old_only hunks drops all New ranges from hunks and converts all Replace ranges to Old ranges.
val new_only : 'a Hunk.t list -> 'a Hunk.t list
new_only hunks drops all Old ranges from hunks and converts all Replace ranges to New ranges.
val ranges : 'a Hunk.t list -> 'a Range.t list
ranges hunks concatenates all the ranges of all hunks together *
type 'a segment = 
|Same of 'a array
|Different of 'a array array
type 'a merged_array = 'a segment list
val merge : 'a array array -> 'a merged_array