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https://github.com/erwald/elm-edit-distance
An Elm package for calculating between-list edit distances
https://github.com/erwald/elm-edit-distance
edit-distance edit-distances elm levenshtein-distance wagner-fischer-algorithm
Last synced: about 8 hours ago
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An Elm package for calculating between-list edit distances
- Host: GitHub
- URL: https://github.com/erwald/elm-edit-distance
- Owner: erwald
- License: mit
- Created: 2016-07-15T22:04:31.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2019-03-03T12:23:19.000Z (almost 6 years ago)
- Last Synced: 2024-12-20T15:12:43.200Z (5 days ago)
- Topics: edit-distance, edit-distances, elm, levenshtein-distance, wagner-fischer-algorithm
- Language: Elm
- Homepage:
- Size: 23.4 KB
- Stars: 3
- Watchers: 1
- Forks: 1
- Open Issues: 4
-
Metadata Files:
- Readme: README.md
- License: LICENSE.md
Awesome Lists containing this project
README
# Edit Distance
An Elm package for calculating between-list edit distances.
It can calculate both the [Levenshtein distance](https://en.wikipedia.org/wiki/Levenshtein_distance) between two lists and the actual edit steps required to go from one list to another (using the [Wagner-Fischer algorithm](https://en.wikipedia.org/wiki/Wagner%E2%80%93Fischer_algorithm)).
```elm
-- Levenshtein.
levenshtein (String.toList "kitten") (String.toList "sitting") == 3
levenshteinFromStrings "garvey" "avery" == 3
-- Edit steps.
edits (String.toList "kitten") (String.toList "sitting") ==
[ Substitute 's' 0
, Substitute 'i' 4
, Insert 'g' 6
]
editsFromStrings "sitting" "kitten" ==
[ Substitute 'k' 0
, Substitute 'e' 4
, Delete 'g' 6
]
-- Edit steps include moves (i.e. deletions followed by insertions).
editsFromStrings "garvey" "avery" ==
[ Delete 'g' 0
, Move 'r' 2 3
]
```
The resulting indices reflect edits where *deletions are made first*, before insertions and substitutions. That is, indices for deletions refer to the source list, whereas indices for insertions and substitutions refer to the latter, intermediate lists.
An example will serve. Calling `editsFromStrings` with `"preterit"` and `"zeitgeist"` returns the following:
```elm
[ Substitute 'z' 0
, Delete 'r' 1
, Insert 'i' 2
, Insert 'g' 4
, Delete 'r' 5
, Insert 's' 7
]
```
Let's look at these steps in order, keeping in mind that deletions are made first:
1. Deleting at index 1 in "p**r**eterit" gives "peterit".
2. Deleting at index 5 in "prete**r**it" gives "peteit".
3. Substituting "z" at index 0 in "**p**eteit" gives "**z**eteit".
4. Inserting "i" at index 2 in "zeteit" gives "ze**i**teit".
5. Inserting "g" at index 4 in "zeiteit" gives "zeit**g**eit".
6. Inserting "s" at index 7 in "zeitgeit" gives "zeitgei**s**t".
## To do
* [x] String support.
* [x] Custom cost function.
* [ ] Memoization.
## Tests
First install [elm-test](http://package.elm-lang.org/packages/elm-community/elm-test/latest):
```sh
$ npm install -g elm-test
```
Then run the tests, and you should see something like this:
```sh
$ elm-test
Success! Compiled 1 module.
Successfully generated /var/folders/kb/lmdz_h5n629b85bbnkxhfx3c0000gn/T/elm_test_1161113-40357-1bh5q3m.e262a3v7vi.js
elm-test
--------
Running 26 tests. To reproduce these results, run: elm-test --seed 514474818
TEST RUN PASSED
Duration: 796 ms
Passed: 26
Failed: 0
```
## Contributing
Contributions are welcome. Just open up an issue if you've found a problem or have a suggestion for a feature, or a pull request if you already know how to fix or implement it.
## Change Log
### 1.1.1
* Update for Elm 0.18.
### 1.1.0
* Adds support for custom cost functions in the form of `editsWithCostFunc` and `editsWithCostFuncFromStrings`.
### 1.0.0
* Initial version, with support for calculating Levenshtein distance and edit steps using the Wagner-Fischer algorithm. Also includes String support.