Merge pull request #34 from giraugh/feat/edit-distance-ops

Add options to editDistance for operation weights

.changeset/wicked-coats-know.md

@@ -0,0 +1,5 @@
+---
+"@giraugh/tools": minor
+---
+
+Add weight options to `editDistance`

lib/strings/editDistance.ts

@@ -1,3 +1,11 @@
+export type EditDistanceOptions = {
+  weights: {
+    insertion?: number,
+    deletion?: number,
+    substition?: number,
+  }
+}
+
 /**
  * Compute the levenshtein edit distance between two strings.
  * Equivalent to the the number of edits necessary to get from source to target.
@@ -7,20 +15,23 @@
  * 
  * @example editDistance('snail', 'mail') === 2
  */
-export const editDistance = (source: string, target: string): number => {
+export const editDistance = (source: string, target: string, options?: Partial<EditDistanceOptions>): number => {
   // Create dynamic programming matrix
   const dynMat = Array(target.length + 1).fill(-1)
     .map((_, i) => Array(source.length + 1).fill(-1)
-      .map((_, j) => i === 0 ? j : (j === 0 ? i : -1) ))
+      .map((_, j) => i === 0
+        ?  j * (options?.weights?.deletion ?? 1) 
+        : (j === 0 ? (i * (options?.weights?.insertion ?? 1)) : -1) ))
+
 
   // Compute the matrix values
   for (let j = 1; j <= target.length; j++) {
     for (let i = 1; i <= source.length; i++) {
       const ind = source[i - 1] === target[j - 1] ? 0 : 1
       dynMat[j][i] = Math.min(
-        dynMat[j][i - 1] + 1, // deletion
-        dynMat[j - 1][i] + 1, // insertion
-        dynMat[j - 1][i - 1] + ind, // substitution
+        dynMat[j][i - 1] + (options?.weights?.deletion ?? 1), // deletion
+        dynMat[j - 1][i] + (options?.weights?.insertion ?? 1), // insertion
+        dynMat[j - 1][i - 1] + (options?.weights?.substition ?? 1) * ind, // substitution
       )
     }
   }
@@ -29,8 +40,6 @@ export const editDistance = (source: string, target: string): number => {
   return dynMat[target.length][source.length]
 }
 
-
-
 // Tests
 if (import.meta.vitest) {
   const { it, expect } = import.meta.vitest
@@ -51,4 +60,10 @@ if (import.meta.vitest) {
   it('correctly calculates the distance between a word and an empty string', () => {
     expect(editDistance('', 'gracious')).toBe(8)
   })
+
+  it('uses provided operation weights', () => {
+    expect(editDistance('', 'abc', { weights: { insertion: 2 } })).toBe(6)
+    expect(editDistance('abc', '', { weights: { deletion: 2 } })).toBe(6)
+    expect(editDistance('abc', 'defg', { weights: { substition: 2, insertion: 3 } })).toBe(9)
+  })
 }