Small, idiomatic Go implementation of the Levenshtein edit distance algorithm. This package provides utilities to compute distances, ratios, edit matrices and edit scripts for sequences of runes (Unicode code points).

It is based on the original texttheater/golang-levenshtein implementation and provides a compact API that is convenient for Go projects that need fuzzy string comparisons, similarity scoring, or to produce edit scripts.

Use Go modules (recommended):

    go get github.com/TomTonic/levenshtein

Then import:

    import "github.com/TomTonic/levenshtein"

Key functions and types you'll use:

• DistanceForStrings(source []rune, target []rune, op Options) int — computes the Levenshtein distance between two rune slices.
• MatrixForStrings(source []rune, target []rune, op Options) [][]int — returns the full DP matrix (useful for backtraces or visualization).
• EditScriptForStrings(source []rune, target []rune, op Options) EditScript — returns an optimal edit script (sequence of ops: Ins, Del, Sub, Match).
• RatioForStrings(source []rune, target []rune, op Options) float64 — returns a normalized similarity ratio.
• DefaultOptions and DefaultOptionsWithSub — convenience Options values.

Go strings are byte sequences and indexing a string yields a byte. For Unicode-aware string comparison you should convert to []rune (which are Unicode code points) before calling this package. That ensures multi-byte characters (e.g. emoji, accented letters) are treated as single elements.

Example: source := "café" and target := "cafe", if you call the library with []rune(source) and []rune(target) you will get correct behavior for Unicode text.

package main

import (
        "fmt"
        "github.com/TomTonic/levenshtein"
)

func main() {
        a := "kitten"
        b := "sitting"
        d := levenshtein.DistanceForStrings([]rune(a), []rune(b), levenshtein.DefaultOptions)
        fmt.Println(d) // prints 5 with DefaultOptions (no substitution)
}

d := levenshtein.DistanceForStrings([]rune("kitten"), []rune("sitting"), levenshtein.DefaultOptionsWithSub)
// d == 3

script := levenshtein.EditScriptForStrings([]rune("a"), []rune("aa"), levenshtein.DefaultOptions)
// script will contain EditOperation values such as Match, Ins, Del, Sub

matrix := levenshtein.MatrixForStrings([]rune("neighbor"), []rune("Neighbour"), levenshtein.DefaultOptions)
levenshtein.WriteMatrix([]rune("neighbor"), []rune("Neighbour"), matrix, os.Stdout)

The Options struct lets you tweak insertion, deletion and substitution costs and also provide a custom Matches function. This is handy for case-insensitive comparisons or language-specific matching.

Example (case-insensitive matching):

import "unicode"

caseInsensitive := levenshtein.Options{
        InsCost: 1,
        DelCost: 1,
        SubCost: 1,
        Matches: func(a, b rune) bool {
                return unicode.ToLower(a) == unicode.ToLower(b)
        },
}

dist := levenshtein.DistanceForStrings([]rune("Apple"), []rune("apple"), caseInsensitive)
// dist == 0

This repository aims to be small, well-tested and CI-driven. Practices for maintaining quality:

• Tests: keep the existing unit tests in levenshtein_test.go. Run them with go test ./... and check coverage with go test ./... -cover.

• Linting: run go vet and a linter such as golangci-lint to catch suspicious code patterns. Example:

    golangci-lint run --enable=govet --enable=staticcheck
  

• Formatting: enforce gofmt (or go fmt) before commits.

For small Go libraries the standard approach is Semantic Versioning using git tags and GitHub Releases.

Contributors are encouraged to include a one-line summary in the PRs header and steps-to-reproduce (test cases) in the body.

Contributions are welcome. Please use GitHub functionality to propose changes.

This project is released under the terms found in the LICENSE file.

This implementation is adapted from the original texttheater/golang-levenshtein project.

If you find issues, please open an issue or a PR on GitHub. For general help or usage questions, include the inputs you used and expected output.