## cl-editdistance

2022-04-01

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# edit-distance

## Using

Computes the edit distance (aka Levenshtein distance) between two sequences. This is a common distance measure.

For example, to compute the distance between two sequences:

```
(edit-distance:distance '(1 2 3 4 5) '(2 3 4 5 6))
```

To compute the sequence of edit operations needed to convert sequence
1 into sequence two, use the `diff`

function

```
(edit-distance:diff '(1 2 3 4 5) '(2 3 4 5 6))
```

That will return two values a structure, as follows, and the distance.

```
((:DELETION 1 NIL) (:MATCH 2 2) (:MATCH 3 3) (:MATCH 4 4) (:MATCH 5 5) (:INSERTION NIL 6))
2
```

That structure can be printed more readibly with the `FORMAT-DIFF`

function

```
(edit-distance:format-diff *path*)
```

Or, you can compute the diff and print it readably together by calling `PRINT-DIFF`

:

```
(edit-distance:print-diff '(1 2 3 4 5) '(2 3 4 5 6))
```

which will print a result like this:

```
seq1: 1 2 3 4 5 *** []
seq2: *** 2 3 4 5 6 []
```

Several options are available to the `FORMAT-DIFF`

and `PRINT-DIFF`

to
print a prefix and suffix for each line. Note that displaying
substitutions relys on captialization and so substitutions are not
visible for non-alphabetic sequence elements.

Additionally, other equality functions can be used, so this evaluates to a distance of zero:

```
(edit-distance:distance '("ONE" "TWO" "THREE") '("one" "two"
"three") :test 'string-equal)
```

Any type of sequence may be used, but for speed the input sequences are copied into new arrays. If speed is a major concern make sure to provide simple vectors as your input sequences.

## Testing

To test with sbcl, run:

```
sbcl --eval "(asdf:load-system 'edit-distance-test)" --eval "(unless (lisp-unit:run-tests :all :edit-distance-tests) (uiop:quit 1))"
```

cl-edit-distance by Ben Lambert is licensed under a Creative Commons Attribution 4.0 International License.