🚧 progress: Import existing sources and tests from js-compare.

README.md

@@ -4,12 +4,12 @@
 Comparison function reversion for JavaScript.
 See [docs](https://total-order.github.io/reversed/index.html).
 
-> :building_construction: Caveat emptor! This is work in progress. Code may be
-> working. Documentation may be present. Coherence may be. Maybe.
+```js
+import {increasing} from '@total-order/primitive';
+import {reversed} from '@total-order/reversed';
 
-> :warning: Depending on your environment, the code may require
-> `regeneratorRuntime` to be defined, for instance by importing
-> [regenerator-runtime/runtime](https://www.npmjs.com/package/regenerator-runtime).
+let decreasing = reversed(increasing);
+```
 
 [![License](https://img.shields.io/github/license/total-order/reversed.svg)](https://raw.githubusercontent.com/total-order/reversed/main/LICENSE)
 [![Version](https://img.shields.io/npm/v/@total-order/reversed.svg)](https://www.npmjs.org/package/@total-order/reversed)

doc/manual/usage.md

@@ -1,19 +1,8 @@
 # Usage
 
-> :warning: Depending on your environment, the code may require
-> `regeneratorRuntime` to be defined, for instance by importing
-> [regenerator-runtime/runtime](https://www.npmjs.com/package/regenerator-runtime).
-
-First, require the polyfill at the entry point of your application
-```js
-require( 'regenerator-runtime/runtime' ) ;
-// or
-import 'regenerator-runtime/runtime.js' ;
-```
-
-Then, import the library where needed
+Import the library where needed
 ```js
-const reversed = require( '@total-order/reversed' ) ;
+const {reversed} = require( '@total-order/reversed' ) ;
 // or
-import * as reversed from '@total-order/reversed' ;
+import {reversed} from '@total-order/reversed' ;
 ```

package.json

@@ -66,6 +66,7 @@
     "@babel/register": "7.13.14",
     "@commitlint/cli": "12.1.1",
     "@js-library/commitlint-config": "0.0.4",
+    "@total-order/primitive": "^0.0.2",
     "ava": "3.15.0",
     "babel-plugin-transform-remove-console": "6.9.4",
     "babel-plugin-unassert": "3.0.1",

src/index.js

@@ -1,2 +1 @@
-const answer = 42;
-export default answer;
+export {default as reversed} from './reversed.js';

src/reversed.js

@@ -0,0 +1,9 @@
+/**
+ * Compile a new comparison function whose underlying total order is the
+ * reverse of the input comparison function's underlying total order.
+ *
+ * @param {Function} compare The comparison function to reverse.
+ * @return {Function} A function f such that compare(a,b) === f(b,a) for all a,b.
+ */
+const reversed = (compare) => (a, b) => compare(b, a);
+export default reversed;

test/src/reversed.js

@@ -0,0 +1,33 @@
+import test from 'ava';
+import {increasing, decreasing} from '@total-order/primitive';
+import {reversed} from '../../src/index.js';
+
+const increasing2 = reversed(decreasing);
+const decreasing2 = reversed(increasing);
+
+const macro = (t, a, b) => {
+	const i = increasing(a, b);
+	const d = decreasing(a, b);
+	const i2 = increasing2(a, b);
+	const d2 = decreasing2(a, b);
+	const ri = increasing(b, a);
+	const rd = decreasing(b, a);
+	const ri2 = increasing2(b, a);
+	const rd2 = decreasing2(b, a);
+
+	t.deepEqual(i, i2, `i i2 (${a}, ${b})`);
+	t.deepEqual(-i, ri, `-i ri (${a}, ${b})`);
+	t.deepEqual(-i, ri2, `-i ri2 (${a}, ${b})`);
+	t.deepEqual(-i, d, `-i d (${a}, ${b})`);
+	t.deepEqual(-i, d2, `-i d2 (${a}, ${b})`);
+	t.deepEqual(i, rd, `i rd (${a}, ${b})`);
+	t.deepEqual(i, rd2, `i rd2 (${a}, ${b})`);
+};
+
+macro.title = (title, a, b) => title ?? `(${a}, ${b})`;
+
+const random = () => Math.random() - 0.5;
+
+for (let n = 0; n < 100; ++n) {
+	test(macro, random(), random());
+}