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add new operation: Levenshtein Distance
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@mikecat
mikecat committed Jan 10, 2023
1 parent ba12ad8 commit 2c82231
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1 change: 1 addition & 0 deletions src/core/config/Categories.json
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Expand Up @@ -269,6 +269,7 @@
"Fuzzy Match",
"Offset checker",
"Hamming Distance",
"Levenshtein Distance",
"Convert distance",
"Convert area",
"Convert mass",
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98 changes: 98 additions & 0 deletions src/core/operations/LevenshteinDistance.mjs
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/**
* @author mikecat
* @copyright Crown Copyright 2023
* @license Apache-2.0
*/

import Operation from "../Operation.mjs";
import OperationError from "../errors/OperationError.mjs";

/**
* Levenshtein Distance operation
*/
class LevenshteinDistance extends Operation {

/**
* LevenshteinDistance constructor
*/
constructor() {
super();

this.name = "Levenshtein Distance";
this.module = "Default";
this.description = "Levenshtein Distance (also known as Edit Distance) is a string metric to measure a difference between two strings that counts operations (insertions, deletions, and substitutions) on single character that are required to change one string to another.";
this.infoURL = "https://wikipedia.org/wiki/Levenshtein_distance";
this.inputType = "string";
this.outputType = "number";
this.args = [
{
name: "Sample delimiter",
type: "binaryString",
value: "\\n"
},
{
name: "Insertion cost",
type: "number",
value: 1
},
{
name: "Deletion cost",
type: "number",
value: 1
},
{
name: "Substitution cost",
type: "number",
value: 1
},
];
}

/**
* @param {string} input
* @param {Object[]} args
* @returns {number}
*/
run(input, args) {
const [delim, insCost, delCost, subCost] = args;
const samples = input.split(delim);
if (samples.length !== 2) {
throw new OperationError("Incorrect number of samples. Check your input and/or delimiter.");
}
if (insCost < 0 || delCost < 0 || subCost < 0) {
throw new OperationError("Negative costs are not allowed.");
}
const src = samples[0], dest = samples[1];
let currentCost = new Array(src.length + 1);
let nextCost = new Array(src.length + 1);
for (let i = 0; i < currentCost.length; i++) {
currentCost[i] = delCost * i;
}
for (let i = 0; i < dest.length; i++) {
const destc = dest.charAt(i);
nextCost[0] = currentCost[0] + insCost;
for (let j = 0; j < src.length; j++) {
let candidate;
// insertion
let optCost = currentCost[j + 1] + insCost;
// deletion
candidate = nextCost[j] + delCost;
if (candidate < optCost) optCost = candidate;
// substitution or matched character
candidate = currentCost[j];
if (src.charAt(j) !== destc) candidate += subCost;
if (candidate < optCost) optCost = candidate;
// store calculated cost
nextCost[j + 1] = optCost;
}
const tempCost = nextCost;
nextCost = currentCost;
currentCost = tempCost;
}

return currentCost[currentCost.length - 1];
}

}

export default LevenshteinDistance;
1 change: 1 addition & 0 deletions tests/operations/index.mjs
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Expand Up @@ -130,6 +130,7 @@ import "./tests/FletcherChecksum.mjs";
import "./tests/CMAC.mjs";
import "./tests/AESKeyWrap.mjs";
import "./tests/Rabbit.mjs";
import "./tests/LevenshteinDistance.mjs";

// Cannot test operations that use the File type yet
// import "./tests/SplitColourChannels.mjs";
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165 changes: 165 additions & 0 deletions tests/operations/tests/LevenshteinDistance.mjs
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/**
* @author mikecat
* @copyright Crown Copyright 2023
* @license Apache-2.0
*/
import TestRegister from "../../lib/TestRegister.mjs";

TestRegister.addTests([
{
"name": "Levenshtein Distance: Wikipedia example 1",
"input": "kitten\nsitting",
"expectedOutput": "3",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 1, 1, 1,
],
},
],
},
{
"name": "Levenshtein Distance: Wikipedia example 2",
"input": "saturday\nsunday",
"expectedOutput": "3",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 1, 1, 1,
],
},
],
},
{
"name": "Levenshtein Distance: Wikipedia example 1 with substitution cost 2",
"input": "kitten\nsitting",
"expectedOutput": "5",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 1, 1, 2,
],
},
],
},
{
"name": "Levenshtein Distance: varied costs 1",
"input": "kitten\nsitting",
"expectedOutput": "230",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 10, 100, 1000,
],
},
],
},
{
"name": "Levenshtein Distance: varied costs 2",
"input": "kitten\nsitting",
"expectedOutput": "1020",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 1000, 100, 10,
],
},
],
},
{
"name": "Levenshtein Distance: another delimiter",
"input": "kitten sitting",
"expectedOutput": "3",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
" ", 1, 1, 1,
],
},
],
},
{
"name": "Levenshtein Distance: too few samples",
"input": "kitten",
"expectedOutput": "Incorrect number of samples. Check your input and/or delimiter.",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 1, 1, 1,
],
},
],
},
{
"name": "Levenshtein Distance: too many samples",
"input": "kitten\nsitting\nkitchen",
"expectedOutput": "Incorrect number of samples. Check your input and/or delimiter.",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 1, 1, 1,
],
},
],
},
{
"name": "Levenshtein Distance: negative insertion cost",
"input": "kitten\nsitting",
"expectedOutput": "Negative costs are not allowed.",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", -1, 1, 1,
],
},
],
},
{
"name": "Levenshtein Distance: negative deletion cost",
"input": "kitten\nsitting",
"expectedOutput": "Negative costs are not allowed.",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 1, -1, 1,
],
},
],
},
{
"name": "Levenshtein Distance: negative substitution cost",
"input": "kitten\nsitting",
"expectedOutput": "Negative costs are not allowed.",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 1, 1, -1,
],
},
],
},
{
"name": "Levenshtein Distance: cost zero",
"input": "kitten\nsitting",
"expectedOutput": "0",
"recipeConfig": [
{
"op": "Levenshtein Distance",
"args": [
"\\n", 0, 0, 0,
],
},
],
},
]);

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