prelude-ls 1.2.1

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:npm/prelude-ls@1.2.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/prelude-ls@1.2.1
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:29b6756f064b622358cea71ee834b7506ccd726059b7106f882819d2ab198b09","constraints":{"executionContext":"node"},"contract":["map transforms elements in an array by applying a unary mapping function","filter keeps elements satisfying a predicate and reject excludes elements satisfying a predicate","partition splits an array into a pair of arrays of elements that pass and fail a predicate","foldl reduces elements from the left with an accumulator and initial value, while foldr reduces from the right","sum computes the arithmetic sum of numbers and product computes their product","take extracts the first n elements and drop removes the first n elements from an array","splitAt partitions an array at a specified index into a tuple of two sub-arrays","takeWhile takes elements while a predicate holds true and dropWhile drops elements while a predicate holds true","head returns the first element, tail returns all except the first, last returns the final element, and initial returns all except the last","unique removes duplicate elements, intersection finds common elements, difference removes elements present in another list, and union merges lists without duplicates","zip pairs corresponding elements from two lists and zipWith combines them using a binary function","groupBy groups elements into an object keyed by the result of a grouping function and sortBy sorts elements by an extracted key","pairsToObj constructs an object from key-value pairs and objToPairs extracts key-value pairs from an object","capitalize, camelize, and dasherize format string casing, and words, unwords, lines, unlines split and join string sequences","curry converts a multi-argument function into a curried function and flip reverses the order of the first two arguments","isType validates the constructor type name of JavaScript values including String, Number, and Array"],"goal":"verify pkg:npm/prelude-ls@1.2.1","kind":"HOW","packages":["pkg:npm/prelude-ls@1.2.1"],"schemaVersion":1},"contractCommand":["node","test/contract.cjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/prelude-ls@1.2.1"],"schemaVersion":1,"subject":"pkg:npm/prelude-ls@1.2.1","verifierAdapter":"node-typescript@1"}

{
  "name": "sample-prelude-ls",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-prelude-ls",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "prelude-ls": "1.2.1"
      }
    },
    "node_modules/prelude-ls": {
      "version": "1.2.1",
      "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.2.1.tgz",
      "integrity": "sha512-vkcDPrRZo1QZLbn5RLGPpg/WmIQ65qoWWhcGKf/b5eplkkarX0m9z8ppCat4mlOqUsWpyNuYgO3VRyrYHSzX5g==",
      "license": "MIT",
      "engines": {
        "node": ">= 0.8.0"
      }
    }
  }
}

{
  "name": "sample-prelude-ls",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for prelude-ls",
  "license": "MIT-0",
  "dependencies": {
    "prelude-ls": "1.2.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/prelude-ls@1.2.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/prelude-ls@1.2.1"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "runtime": "node@22.23.2"
  }
}

const assert = require('node:assert');
const prelude = require('prelude-ls');

const {
  map,
  filter,
  reject,
  partition,
  foldl,
  foldr,
  sum,
  product,
  take,
  drop,
  splitAt,
  takeWhile,
  dropWhile,
  head,
  tail,
  last,
  initial,
  reverse,
  unique,
  intersection,
  difference,
  union,
  zip,
  zipWith,
  groupBy,
  sortBy,
  pairsToObj,
  objToPairs,
  keys,
  values,
  capitalize,
  camelize,
  dasherize,
  words,
  unwords,
  lines,
  unlines,
  curry,
  flip,
  isType,
} = prelude;

// 1. map transforms elements in an array by applying a unary mapping function
const mapped = map((x) => x * 2, [1, 2, 3]);
assert.deepStrictEqual(mapped, [2, 4, 6]);

// 2. filter keeps elements satisfying a predicate and reject excludes elements satisfying a predicate
const filtered = filter((x) => x % 2 === 0, [1, 2, 3, 4, 5]);
assert.deepStrictEqual(filtered, [2, 4]);
const rejected = reject((x) => x % 2 === 0, [1, 2, 3, 4, 5]);
assert.deepStrictEqual(rejected, [1, 3, 5]);

// 3. partition splits an array into a pair of arrays of elements that pass and fail a predicate
const partitioned = partition((x) => x > 2, [1, 2, 3, 4, 5]);
assert.deepStrictEqual(partitioned, [
  [3, 4, 5],
  [1, 2],
]);

// 4. foldl reduces elements from the left with an accumulator and initial value, while foldr reduces from the right
const foldedLeft = foldl((acc, x) => acc - x, 10, [1, 2, 3]); // ((10 - 1) - 2) - 3 = 4
assert.strictEqual(foldedLeft, 4);
const foldedRight = foldr((x, acc) => x - acc, 0, [1, 2, 3, 4]); // 1 - (2 - (3 - (4 - 0))) = -2
assert.strictEqual(foldedRight, -2);

// 5. sum computes the arithmetic sum of numbers and product computes their product
assert.strictEqual(sum([10, 20, 30, 5]), 65);
assert.strictEqual(sum([]), 0);
assert.strictEqual(product([2, 3, 4, 5]), 120);
assert.strictEqual(product([]), 1);

// 6. take extracts the first n elements and drop removes the first n elements from an array
assert.deepStrictEqual(take(2, [10, 20, 30, 40]), [10, 20]);
assert.deepStrictEqual(take(0, [10, 20, 30]), []);
assert.deepStrictEqual(drop(2, [10, 20, 30, 40]), [30, 40]);
assert.deepStrictEqual(drop(5, [10, 20]), []);

// 7. splitAt partitions an array at a specified index into a tuple of two sub-arrays
assert.deepStrictEqual(splitAt(2, ['a', 'b', 'c', 'd']), [
  ['a', 'b'],
  ['c', 'd'],
]);
assert.deepStrictEqual(splitAt(0, ['a', 'b']), [[], ['a', 'b']]);

// 8. takeWhile takes elements while a predicate holds true and dropWhile drops elements while a predicate holds true
assert.deepStrictEqual(takeWhile((x) => x < 4, [1, 2, 3, 5, 2, 1]), [1, 2, 3]);
assert.deepStrictEqual(dropWhile((x) => x < 4, [1, 2, 3, 5, 2, 1]), [5, 2, 1]);

// 9. head returns the first element, tail returns all except the first, last returns the final element, and initial returns all except the last
assert.strictEqual(head([10, 20, 30]), 10);
assert.deepStrictEqual(tail([10, 20, 30]), [20, 30]);
assert.strictEqual(last([10, 20, 30]), 30);
assert.deepStrictEqual(initial([10, 20, 30]), [10, 20]);
assert.deepStrictEqual(reverse([1, 2, 3]), [3, 2, 1]);

// 10. unique removes duplicate elements, intersection finds common elements, difference removes elements present in another list, and union merges lists without duplicates
assert.deepStrictEqual(unique([1, 2, 2, 3, 1, 4]), [1, 2, 3, 4]);
assert.deepStrictEqual(intersection([1, 2, 3], [2, 3, 4]), [2, 3]);
assert.deepStrictEqual(difference([1, 2, 3, 4], [2, 4]), [1, 3]);
assert.deepStrictEqual(union([1, 2], [2, 3, 4]), [1, 2, 3, 4]);

// 11. zip pairs corresponding elements from two lists and zipWith combines them using a binary function
assert.deepStrictEqual(zip(['x', 'y', 'z'], [1, 2, 3]), [
  ['x', 1],
  ['y', 2],
  ['z', 3],
]);
assert.deepStrictEqual(zipWith((a, b) => `${a}:${b}`, ['a', 'b'], [10, 20]), [
  'a:10',
  'b:20',
]);

// 12. groupBy groups elements into an object keyed by the result of a grouping function and sortBy sorts elements by an extracted key
const grouped = groupBy((s) => s.length, ['a', 'bb', 'c', 'ddd', 'ee']);
assert.deepStrictEqual(grouped, {
  '1': ['a', 'c'],
  '2': ['bb', 'ee'],
  '3': ['ddd'],
});
const sorted = sortBy((item) => item.score, [
  { id: 1, score: 30 },
  { id: 2, score: 10 },
  { id: 3, score: 20 },
]);
assert.deepStrictEqual(sorted, [
  { id: 2, score: 10 },
  { id: 3, score: 20 },
  { id: 1, score: 30 },
]);

// 13. pairsToObj constructs an object from key-value pairs and objToPairs extracts key-value pairs from an object
assert.deepStrictEqual(
  pairsToObj([
    ['foo', 1],
    ['bar', 2],
  ]),
  { foo: 1, bar: 2 }
);
assert.deepStrictEqual(objToPairs({ alpha: 10, beta: 20 }), [
  ['alpha', 10],
  ['beta', 20],
]);
assert.deepStrictEqual(keys({ a: 1, b: 2 }), ['a', 'b']);
assert.deepStrictEqual(values({ a: 1, b: 2 }), [1, 2]);

// 14. capitalize, camelize, and dasherize format string casing, and words, unwords, lines, unlines split and join string sequences
assert.strictEqual(capitalize('prelude'), 'Prelude');
assert.strictEqual(camelize('functional-programming-helper'), 'functionalProgrammingHelper');
assert.strictEqual(dasherize('functionalProgrammingHelper'), 'functional-programming-helper');
assert.deepStrictEqual(words('foo bar baz'), ['foo', 'bar', 'baz']);
assert.strictEqual(unwords(['foo', 'bar', 'baz']), 'foo bar baz');
assert.deepStrictEqual(lines('line1\nline2\nline3'), ['line1', 'line2', 'line3']);
assert.strictEqual(unlines(['line1', 'line2']), 'line1\nline2');

// 15. curry converts a multi-argument function into a curried function and flip reverses the order of the first two arguments
const add3 = (a, b, c) => a + b + c;
const curriedAdd3 = curry(add3);
assert.strictEqual(curriedAdd3(1)(2)(3), 6);
assert.strictEqual(curriedAdd3(1, 2)(3), 6);
assert.strictEqual(curriedAdd3(1)(2, 3), 6);

const subtract = (a, b) => a - b;
const flippedSubtract = flip(subtract);
assert.strictEqual(flippedSubtract(2, 10), 8);

// 16. isType validates the constructor type name of JavaScript values including String, Number, and Array
assert.strictEqual(isType('String', 'hello'), true);
assert.strictEqual(isType('String', 123), false);
assert.strictEqual(isType('Number', 42), true);
assert.strictEqual(isType('Array', [1, 2, 3]), true);
assert.strictEqual(isType('Object', { a: 1 }), true);
assert.strictEqual(isType('Function', () => {}), true);

console.log('Contract passed');