412 lines
8.1 KiB
JavaScript
412 lines
8.1 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* eslint-disable no-restricted-syntax, no-invalid-this */
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'use strict';
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// MODULES //
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var setReadOnly = require( './../../define-nonenumerable-read-only-property' );
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var setReadOnlyAccessor = require( './../../define-nonenumerable-read-only-accessor' );
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var iteratorSymbol = require( '@stdlib/symbol/iterator' );
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// MAIN //
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/**
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* Stack constructor.
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*
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* @constructor
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* @returns {Stack} stack instance
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*
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* @example
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* var s = new Stack();
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Remove the top value:
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* var v = s.pop();
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* // returns 'bar'
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*
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* // Add a new value to the stack:
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* s.push( 'beep' );
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*
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* // Remove the top value:
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* v = s.pop();
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* // returns 'beep'
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*/
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function Stack() {
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if ( !(this instanceof Stack) ) {
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return new Stack();
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}
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// Use a dynamic array as insertion and deletion is O(1) amortized:
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this._buffer = [];
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return this;
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}
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/**
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* Clears the stack.
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*
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* @name clear
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* @memberof Stack.prototype
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* @type {Function}
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* @returns {Stack} stack instance
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*
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* @example
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* var s = new Stack();
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Peek at the top value:
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* var v = s.first();
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* // returns 'bar'
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*
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* // Examine the stack length:
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* var len = s.length;
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* // returns 2
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*
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* // Clear all stack items:
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* s.clear();
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*
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* // Peek at the top value:
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* v = s.first();
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* // returns undefined
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*
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* // Examine the stack length:
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* len = s.length;
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* // returns 0
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*/
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setReadOnly( Stack.prototype, 'clear', function clear() {
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this._buffer.length = 0;
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return this;
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});
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/**
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* Returns the top value (i.e., the value which is "first-out").
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*
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* @name first
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* @memberof Stack.prototype
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* @type {Function}
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* @returns {(*|void)} top value
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*
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* @example
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* var s = new Stack();
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Peek at the top value:
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* var v = s.first();
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* // returns 'bar'
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*/
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setReadOnly( Stack.prototype, 'first', function first() {
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if ( this._buffer.length ) {
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return this._buffer[ this._buffer.length-1 ];
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}
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});
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/**
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* Returns an iterator for iterating over a stack.
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*
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* ## Notes
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*
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* - In order to prevent confusion arising from stack mutation during iteration, a returned iterator **always** iterates over a stack "snapshot", which is defined as the list of stack elements at the time of this method's invocation.
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*
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* @name iterator
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* @memberof Stack.prototype
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* @type {Function}
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* @returns {Iterator} iterator
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*
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* @example
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* var s = new Stack();
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Create an iterator:
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* var it = s.iterator();
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*
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* // Iterate over the stack...
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* var v = it.next().value;
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* // returns 'bar'
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*
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* v = it.next().value;
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* // returns 'foo'
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*
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* var bool = it.next().done;
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* // returns true
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*/
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setReadOnly( Stack.prototype, 'iterator', function iterator() {
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var values;
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var iter;
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var self;
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var FLG;
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var i;
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self = this;
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// Initialize the iteration index:
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i = this._buffer.length;
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// Create a copy of stack values (necessary in order to "snapshot" the stack; otherwise, values could come and go between calls to `next`):
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values = this._buffer.slice();
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// Create an iterator protocol-compliant object:
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iter = {};
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setReadOnly( iter, 'next', next );
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setReadOnly( iter, 'return', end );
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if ( iteratorSymbol ) {
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setReadOnly( iter, iteratorSymbol, factory );
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}
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return iter;
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/**
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* Returns an iterator protocol-compliant object containing the next iterated value.
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*
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* @private
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* @returns {Object} iterator protocol-compliant object
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*/
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function next() {
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i -= 1;
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if ( FLG || i < 0 ) {
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return {
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'done': true
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};
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}
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return {
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'value': values[ i ],
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'done': false
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};
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}
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/**
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* Finishes an iterator.
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*
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* @private
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* @param {*} [value] - value to return
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* @returns {Object} iterator protocol-compliant object
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*/
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function end( value ) {
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FLG = true;
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if ( arguments.length ) {
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return {
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'value': value,
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'done': true
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};
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}
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return {
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'done': true
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};
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}
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/**
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* Returns a new iterator.
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*
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* @private
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* @returns {Iterator} iterator
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*/
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function factory() {
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return self.iterator();
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}
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});
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/**
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* Returns the bottom stack value (i.e., the value which is currently "last-out").
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*
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* @name last
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* @memberof Stack.prototype
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* @type {Function}
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* @returns {(*|void)} bottom stack value
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*
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* @example
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* var s = new Stack();
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Peek at the bottom value:
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* var v = s.last();
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* // returns 'foo'
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*/
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setReadOnly( Stack.prototype, 'last', function last() {
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if ( this._buffer.length ) {
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return this._buffer[ 0 ];
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}
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});
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/**
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* Stack length.
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*
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* @name length
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* @memberof Stack.prototype
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* @type {NonNegativeInteger}
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*
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* @example
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* var s = new Stack();
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*
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* // Examine the initial stack length:
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* var len = s.length;
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* // returns 0
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Retrieve the current stack length:
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* len = s.length;
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* // returns 2
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*/
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setReadOnlyAccessor( Stack.prototype, 'length', function get() {
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return this._buffer.length;
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});
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/**
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* Removes a value from the stack.
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*
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* @name pop
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* @memberof Stack.prototype
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* @type {Function}
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* @returns {(*|void)} removed value
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*
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* @example
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* var s = new Stack();
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Remove the top value:
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* var v = s.pop();
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* // returns 'bar'
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*
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* // Add a new value to the stack:
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* s.push( 'beep' );
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*
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* // Remove the top value:
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* v = s.pop();
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* // returns 'beep'
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*/
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setReadOnly( Stack.prototype, 'pop', function pop() {
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if ( this._buffer.length ) {
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return this._buffer.pop();
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}
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});
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/**
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* Adds a value to the stack.
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*
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* @name push
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* @memberof Stack.prototype
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* @type {Function}
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* @returns {Stack} stack instance
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*
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* @example
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* var s = new Stack();
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Remove the top value:
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* var v = s.pop();
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* // returns 'bar'
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*
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* // Add a new value to the stack:
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* s.push( 'beep' );
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*
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* // Remove the top value:
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* v = s.pop();
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* // returns 'beep'
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*/
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setReadOnly( Stack.prototype, 'push', function push( value ) {
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this._buffer.push( value );
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return this;
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});
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/**
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* Returns an array of stack values.
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*
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* ## Notes
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*
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* - Why reverse insertion order? Pros and cons to either order, but reverse insertion order mirrors iterator order. For example, we can use the ES6/ES2015+ spread operator along with the iterator to return stack values.
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*
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* ```text
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* arr = [...s.iterator()]
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* ```
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*
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* One might (as is the opinion here) consider parity of array serialization and iterator order to be a reasonable design goal.
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*
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* @name toArray
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* @memberof Stack.prototype
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* @type {Function}
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* @returns {Array} stack values
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*
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* @example
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* var s = new Stack();
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Get an array of stack values:
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* var vals = s.toArray();
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* // returns [ 'bar', 'foo' ]
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*/
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setReadOnly( Stack.prototype, 'toArray', function toArray() {
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var out;
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var i;
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out = [];
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for ( i = this._buffer.length-1; i >= 0; i-- ) {
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out.push( this._buffer[ i ] );
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}
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return out;
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});
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/**
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* Serializes a stack as JSON.
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*
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* ## Notes
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*
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* - `JSON.stringify()` implicitly calls this method when stringifying a `Stack` instance.
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*
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* @name toJSON
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* @memberof Stack.prototype
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* @type {Function}
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* @returns {Object} serialized stack
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*
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* @example
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* var s = new Stack();
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*
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* // Add values to the stack:
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* s.push( 'foo' ).push( 'bar' );
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*
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* // Serialize to JSON:
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* var o = s.toJSON();
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* // returns { 'type': 'stack', 'data': [ 'bar', 'foo' ] }
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*/
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setReadOnly( Stack.prototype, 'toJSON', function toJSON() {
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var out = {};
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out.type = 'stack';
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out.data = this.toArray();
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return out;
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});
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// EXPORTS //
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module.exports = Stack;
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