A translation of Google's public-domain diff_match_patch code into pure Elixir.

For information about the original Google project and its application, see that repository's wiki pages.

References from the Google project:

• diff: An O(ND) Difference Algorithm and Its Variations (Meyers, 1986)
• match: Fast Text Searching with Errors (Wu and Manber, 1991)

Prior art on the BEAM:

• diffy: A Diff, Match and Patch implementation for Erlang

If available in Hex, the package can be installed by adding diff_match_patch to your list of dependencies in mix.exs:

def deps do
  [
    {:diff_match_patch, "~> 0.2.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/cursor.

1. Find a match for a pattern inside at text using fuzzy search. The match_threshold option determines the exactness required:

loc = Dmp.Match.main(
    "I am the very model of a modern major general.",
    " that berry ",
    5,
     match_threshold: 0.7)

The value of loc is 4, finding the closest match at the string starting " the very". If no close match is found, the loc returned is -1.

2. Create a diff between two texts:

diffs = Dmp.Diff.main(
    "The quick brown fox jumps over the lazy dog.",
    "That quick brown fox jumped over a lazy dog.")

3. Create a patch from the the original text and the diff we just created. The patch can also be created directly from the two texts. These two patches are equal:

patches1 = Dmp.Patch.make(
    "The quick brown fox jumps over the lazy dog.", diffs)
patches2 = Dmp.Patch.make(
    "The quick brown fox jumps over the lazy dog.",
    "That quick brown fox jumped over a lazy dog.")

4. Apply the patch to a third text:

{new_text, matched} = Patch.apply(patches, "The quick red rabbit jumps over the tired tiger.")
IO.puts(new_text)

The new_text prints out as "That quick red rabbit jumped over a tired tiger." The matched value is a list of booleans, showing whether the results of whether matches were made between the (expanded) list of patches and the third text.