🚴 perf(prepend): Prepend by concatenation instead of consing.

Author: make-github-pseudonymous-again

src/3-tree/base/Tree.js

@@ -1,5 +1,3 @@
-import {prepend} from '../../0-core/index.js';
-
 /**
  * Base class for all implementations.
  */
@@ -95,6 +93,6 @@ Tree.prototype.dropUntil = function (predicate) {
  *
  * @returns {Tree} The output tree.
  */
-Tree.prototype.prepend = function (iterable) {
-	return prepend(this, iterable);
-};
+// Tree.prototype.prepend = function (iterable) {
+// return prepend(this, iterable);
+// };

src/3-tree/implementations/0-Empty.js

@@ -48,9 +48,11 @@ Empty.prototype.cons = function (value) {
 	return new Single(this.M, value);
 };
 
-Empty.prototype.append = function (iterable) {
-	return _from_by_filling(this.M, iterable);
-};
+Empty.prototype.prepend =
+	// eslint-disable-next-line no-multi-assign
+	Empty.prototype.append = function (iterable) {
+		return _from_by_filling(this.M, iterable);
+	};
 
 Empty.prototype.concat = function (other) {
 	assert(other instanceof Tree);

src/3-tree/implementations/1-Single.js

@@ -4,8 +4,8 @@ import {cache, Split} from '../../0-core/index.js';
 import {One} from '../../1-digit/index.js';
 import _append_small_list from '../../0-core/_fast/_append_small_list.js';
 import {_from_medium_list} from '../../0-core/_fast/_from_medium_list.js';
-import _fill_right from '../../0-core/_fast/_fill_right.js';
 import isSameMeasure from '../../_debug/isSameMeasure.js';
+import _from_by_filling from '../../0-core/_fast/_from_by_filling.js';
 import {Empty, Deep} from './index.js';
 
 export function Single(M, value) {
@@ -60,17 +60,12 @@ Single.prototype._UNSAFE_push =
 		);
 	};
 
-Single.prototype.append = function (iterable) {
-	const it = iterable[Symbol.iterator]();
-
-	const event = it.next();
-	if (event.done) return this;
-	const x1 = event.value;
-
-	const left = new One(this.a);
-	const middle = new Empty(cache(this.M));
+Single.prototype.prepend = function (iterable) {
+	return _from_by_filling(this.M, iterable).push(this.a);
+};
 
-	return _fill_right(this.M, left, middle, x1, it);
+Single.prototype.append = function (iterable) {
+	return _from_by_filling(this.M, iterable).cons(this.a);
 };
 
 Single.prototype.concat = function (other) {

src/3-tree/implementations/2-Deep.js

@@ -7,6 +7,7 @@ import _prepend_small_list from '../../0-core/_fast/_prepend_small_list.js';
 import _fill_right from '../../0-core/_fast/_fill_right.js';
 import isSameMeasure from '../../_debug/isSameMeasure.js';
 import _append_small_list from '../../0-core/_fast/_append_small_list.js';
+import _from_by_filling from '../../0-core/_fast/_from_by_filling.js';
 import {Empty} from './0-Empty.js';
 import {Single} from './1-Single.js';
 
@@ -119,6 +120,10 @@ Deep.prototype._UNSAFE_push = function (value) {
 	return this._right._UNSAFE_push(this, value);
 };
 
+Deep.prototype.prepend = function (iterable) {
+	return _from_by_filling(this.M, iterable).concat(this);
+};
+
 Deep.prototype.append = function (iterable) {
 	const it = iterable[Symbol.iterator]();