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.

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contains two arrays: elements in the first array are elements found only in the original, old array which have been replaced by elements in the second array, which are elements found only in the new array.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