♻️ refactor: Give better name.

Author: make-github-pseudonymous-again

README.md

@@ -10,8 +10,8 @@ See [docs](https://set-theory.github.io/closure/index.html).
 
 
 ```js
-import {closure} from '@set-theory/closure';
-closure( x => x + 1 , 0 ) ; // 0 1 2 3 ...
+import {singletonUnderUnaryOperator} from '@set-theory/closure';
+singletonUnderUnaryOperator( x => x + 1 , 0 ) ; // 0 1 2 3 ...
 ```
 
 [![License](https://img.shields.io/github/license/set-theory/closure.svg)](https://raw.githubusercontent.com/set-theory/closure/main/LICENSE)

src/closure.js

@@ -1 +1 @@
-export {default as closure} from './closure.js';
+export {default as singletonUnderUnaryOperator} from './singletonUnderUnaryOperator.js';

src/index.js

@@ -0,0 +1,32 @@
+/**
+ * Computes the closure of a unary operator, starting from a single element.
+ *
+ * @experimental Should handle multiple d-ary operators and an arbitrary
+ * cardinality countable set in the future. An actual closure function would
+ * keep track of encountered elements to stop when all elements have been
+ * found. We can have multiple low-level function that enumerate candidates,
+ * and a helper function that constructs a new set out of a combination of
+ * those. Note that the arity of a JavaScript function can be retrieved through
+ * the `length` property.
+ *
+ * @example
+ * singletonUnderUnaryOperator( x => x + 1 , 0 ) ; // 0 1 2 3 ...
+ *
+ * @example
+ * singletonUnderUnaryOperator( x => x * 2 , 1 ) ; // 1 2 4 8 ...
+ *
+ * @param {Function} operator The operator.
+ * @param {Object} start The starting element.
+ * @returns {Iterator} Iterator over the closure.
+ */
+export default function* singletonUnderUnaryOperator(operator, start) {
+	yield start;
+
+	let element = start;
+
+	while (true) {
+		element = operator(element);
+
+		yield element;
+	}
+}

src/singletonUnderUnaryOperator.js

@@ -4,7 +4,7 @@ import {list} from '@iterable-iterator/list';
 import {enumerate} from '@iterable-iterator/zip';
 import {takewhile} from '@iterable-iterator/slice';
 
-import {closure} from '../../src/index.js';
+import {singletonUnderUnaryOperator} from '../../src/index.js';
 
 // https://oeis.org/A006577
 const Collatz = (x) => (x % 2 === 1 ? 3 * x + 1 : Math.floor(x / 2));
@@ -85,12 +85,14 @@ const A006577 = [
 ];
 
 function macro(t, n, a) {
-	const sequence = list(takewhile((x) => x !== 1, closure(Collatz, n)));
+	const sequence = list(
+		takewhile((x) => x !== 1, singletonUnderUnaryOperator(Collatz, n)),
+	);
 
 	t.is(sequence.length, a);
 }
 
-macro.title = (_, n, a) => `closure [A006577] > a(${n}) = ${a}`;
+macro.title = (_, n, a) => `[A006577] > a(${n}) = ${a}`;
 
 for (const [n, a] of enumerate(A006577, 1)) {
 	test(macro, n, a);