time-to-botec

main.js (6804B)

---

 /**
 * @license Apache-2.0
 *
 * Copyright (c) 2018 The Stdlib Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
 'use strict';
 
 // MODULES //
 
 var setReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
 var setReadOnlyAccessor = require( '@stdlib/utils/define-nonenumerable-read-only-accessor' );
 var setReadWriteAccessor = require( '@stdlib/utils/define-nonenumerable-read-write-accessor' );
 var constantFunction = require( '@stdlib/utils/constant-function' );
 var noop = require( '@stdlib/utils/noop' );
 var copy = require( '@stdlib/utils/copy' );
 var isPositiveNumber = require( '@stdlib/assert/is-positive-number' ).isPrimitive;
 var isObject = require( '@stdlib/assert/is-plain-object' );
 var isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
 var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive;
 var hasOwnProp = require( '@stdlib/assert/has-own-property' );
 var MAX_VALUE = require( '@stdlib/constants/float64/max' );
 var rerlang = require( './../../../base/erlang' ).factory;
 var iteratorSymbol = require( '@stdlib/symbol/iterator' );
 
 
 // MAIN //
 
 /**
 * Returns an iterator for generating pseudorandom numbers drawn from an Erlang distribution.
 *
 * @param {PositiveInteger} k - shape parameter
 * @param {PositiveNumber} lambda  - rate parameter
 * @param {Options} [options] - function options
 * @param {PRNG} [options.prng] - pseudorandom number generator which generates uniformly distributed pseudorandom numbers
 * @param {PRNGSeedMT19937} [options.seed] - pseudorandom number generator seed
 * @param {PRNGStateMT19937} [options.state] - pseudorandom number generator state
 * @param {boolean} [options.copy=true] - boolean indicating whether to copy a provided pseudorandom number generator state
 * @param {NonNegativeInteger} [options.iter] - number of iterations
 * @throws {TypeError} `k` must be a positive integer
 * @throws {TypeError} `lambda` must be a positive number
 * @throws {TypeError} options argument must be an object
 * @throws {TypeError} must provide valid options
 * @throws {Error} must provide a valid state
 * @returns {Iterator} iterator
 *
 * @example
 * var iter = iterator( 2, 5.0 );
 *
 * var r = iter.next().value;
 * // returns <number>
 *
 * r = iter.next().value;
 * // returns <number>
 *
 * r = iter.next().value;
 * // returns <number>
 *
 * // ...
 */
 function iterator( k, lambda, options ) {
 	var opts;
 	var iter;
 	var rand;
 	var FLG;
 	var i;
 	if ( !isPositiveInteger( k ) ) {
 		throw new TypeError( 'invalid argument. First argument must be a positive integer. Value: `'+k+'`.' );
 	}
 	if ( !isPositiveNumber( lambda ) ) {
 		throw new TypeError( 'invalid argument. Second argument must be a positive number. Value: `'+lambda+'`.' );
 	}
 	if ( arguments.length > 2 ) {
 		if ( !isObject( options ) ) {
 			throw new TypeError( 'invalid argument. Options argument must be an object. Value: `'+options+'`.' );
 		}
 		opts = copy( options, 1 );
 		if ( hasOwnProp( opts, 'iter' ) ) {
 			if ( !isNonNegativeInteger( opts.iter ) ) {
 				throw new TypeError( 'invalid option. `iter` option must be a nonnegative integer. Option: `'+opts.iter+'`.' );
 			}
 		} else {
 			opts.iter = MAX_VALUE;
 		}
 		rand = rerlang( k, lambda, opts );
 		if ( opts.prng === void 0 && opts.copy !== false ) {
 			opts.state = rand.state; // cache a copy of the PRNG state
 		}
 	} else {
 		rand = rerlang( k, lambda );
 		opts = {
 			'iter': MAX_VALUE,
 			'state': rand.state // cache a copy of the PRNG state
 		};
 	}
 	i = 0;
 
 	// Create an iterator protocol-compliant object:
 	iter = {};
 	setReadOnly( iter, 'next', next );
 	setReadOnly( iter, 'return', end );
 
 	if ( opts && opts.prng ) {
 		setReadOnly( iter, 'seed', null );
 		setReadOnly( iter, 'seedLength', null );
 		setReadWriteAccessor( iter, 'state', constantFunction( null ), noop );
 		setReadOnly( iter, 'stateLength', null );
 		setReadOnly( iter, 'byteLength', null );
 	} else {
 		setReadOnlyAccessor( iter, 'seed', getSeed );
 		setReadOnlyAccessor( iter, 'seedLength', getSeedLength );
 		setReadWriteAccessor( iter, 'state', getState, setState );
 		setReadOnlyAccessor( iter, 'stateLength', getStateLength );
 		setReadOnlyAccessor( iter, 'byteLength', getStateSize );
 	}
 	setReadOnly( iter, 'PRNG', rand.PRNG );
 
 	// If an environment supports `Symbol.iterator`, make the iterator iterable:
 	if ( iteratorSymbol ) {
 		setReadOnly( iter, iteratorSymbol, factory );
 	}
 	return iter;
 
 	/**
 	* Returns an iterator protocol-compliant object containing the next iterated value.
 	*
 	* @private
 	* @returns {Object} iterator protocol-compliant object
 	*/
 	function next() {
 		i += 1;
 		if ( FLG || i > opts.iter ) {
 			return {
 				'done': true
 			};
 		}
 		return {
 			'value': rand(),
 			'done': false
 		};
 	}
 
 	/**
 	* Finishes an iterator.
 	*
 	* @private
 	* @param {*} [value] - value to return
 	* @returns {Object} iterator protocol-compliant object
 	*/
 	function end( value ) {
 		FLG = true;
 		if ( arguments.length ) {
 			return {
 				'value': value,
 				'done': true
 			};
 		}
 		return {
 			'done': true
 		};
 	}
 
 	/**
 	* Returns a new iterator.
 	*
 	* @private
 	* @returns {Iterator} iterator
 	*/
 	function factory() {
 		return iterator( k, lambda, opts );
 	}
 
 	/**
 	* Returns the PRNG seed.
 	*
 	* @private
 	* @returns {PRNGSeedMT19937} seed
 	*/
 	function getSeed() {
 		return rand.PRNG.seed;
 	}
 
 	/**
 	* Returns the PRNG seed length.
 	*
 	* @private
 	* @returns {PositiveInteger} seed length
 	*/
 	function getSeedLength() {
 		return rand.PRNG.seedLength;
 	}
 
 	/**
 	* Returns the PRNG state length.
 	*
 	* @private
 	* @returns {PositiveInteger} state length
 	*/
 	function getStateLength() {
 		return rand.PRNG.stateLength;
 	}
 
 	/**
 	* Returns the PRNG state size (in bytes).
 	*
 	* @private
 	* @returns {PositiveInteger} state size (in bytes)
 	*/
 	function getStateSize() {
 		return rand.PRNG.byteLength;
 	}
 
 	/**
 	* Returns the current pseudorandom number generator state.
 	*
 	* @private
 	* @returns {PRNGStateMT19937} current state
 	*/
 	function getState() {
 		return rand.PRNG.state;
 	}
 
 	/**
 	* Sets the pseudorandom number generator state.
 	*
 	* @private
 	* @param {PRNGStateMT19937} s - generator state
 	* @throws {Error} must provide a valid state
 	*/
 	function setState( s ) {
 		rand.PRNG.state = s;
 	}
 }
 
 
 // EXPORTS //
 
 module.exports = iterator;