time-to-botec

factory.js (7083B)

---

 /**
 * @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 isObject = require( '@stdlib/assert/is-plain-object' );
 var isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
 var hasOwnProp = require( '@stdlib/assert/has-own-property' );
 var constantFunction = require( '@stdlib/utils/constant-function' );
 var noop = require( '@stdlib/utils/noop' );
 var typedarray2json = require( '@stdlib/array/to-json' );
 var defaults = require( './defaults.json' );
 var PRNGS = require( './prngs.js' );
 
 
 // MAIN //
 
 /**
 * Returns a pseudorandom number generator for numbers from a standard normal distribution.
 *
 * @param {Options} [options] - function options
 * @param {string} [options.name='improved-ziggurat'] - name of pseudorandom number generator
 * @param {PRNG} [options.prng] - pseudorandom number generator which generates uniformly distributed pseudorandom numbers
 * @param {*} [options.seed] - pseudorandom number generator seed
 * @param {*} [options.state] - pseudorandom number generator state
 * @param {boolean} [options.copy=true] - boolean indicating whether to copy a provided pseudorandom number generator state
 * @throws {TypeError} must provide an object
 * @throws {TypeError} must provide valid options
 * @throws {Error} must provide the name of a supported pseudorandom number generator
 * @returns {PRNG} pseudorandom number generator
 *
 * @example
 * var randn = factory();
 *
 * var v = randn();
 * // returns <number>
 *
 * @example
 * var randn = factory({
 *     'name': 'box-muller'
 * });
 * var v = randn();
 * // returns <number>
 *
 * @example
 * var randn = factory({
 *     'seed': 12345
 * });
 * var v = randn();
 * // returns <number>
 *
 * @example
 * var randn = factory({
 *     'name': 'box-muller',
 *     'seed': 12345
 * });
 * var v = randn();
 * // returns <number>
 */
 function factory( options ) {
 	var opts;
 	var rand;
 	var prng;
 
 	opts = {
 		'name': defaults.name,
 		'copy': defaults.copy
 	};
 	if ( arguments.length ) {
 		if ( !isObject( options ) ) {
 			throw new TypeError( 'invalid argument. Must provide an object. Value: `' + options + '`.' );
 		}
 		if ( hasOwnProp( options, 'name' ) ) {
 			opts.name = options.name;
 		}
 		if ( hasOwnProp( options, 'prng' ) ) {
 			opts.prng = options.prng;
 			if ( opts.prng === void 0 ) {
 				throw new TypeError( 'invalid option. `prng` option cannot be undefined. Option: `' + opts.prng + '`.' );
 			}
 		} else if ( hasOwnProp( options, 'state' ) ) {
 			opts.state = options.state;
 			if ( opts.state === void 0 ) {
 				throw new TypeError( 'invalid option. `state` option cannot be undefined. Option: `' + opts.state + '`.' );
 			}
 		} else if ( hasOwnProp( options, 'seed' ) ) {
 			opts.seed = options.seed;
 			if ( opts.seed === void 0 ) {
 				throw new TypeError( 'invalid option. `seed` option cannot be undefined. Option: `' + opts.seed + '`.' );
 			}
 		}
 		if ( hasOwnProp( options, 'copy' ) ) {
 			opts.copy = options.copy;
 			if ( !isBoolean( opts.copy ) ) {
 				throw new TypeError( 'invalid option. `copy` option must be a boolean. Option: `' + opts.copy + '`.' );
 			}
 		}
 	}
 	prng = PRNGS[ opts.name ];
 	if ( prng === void 0 ) {
 		throw new Error( 'invalid option. Unrecognized/unsupported PRNG. Option: `' + opts.name + '`.' );
 	}
 	if ( opts.prng === void 0 ) {
 		if ( opts.state === void 0 ) {
 			if ( opts.seed === void 0 ) {
 				rand = prng.factory();
 			} else {
 				rand = prng.factory({
 					'seed': opts.seed
 				});
 			}
 		} else {
 			rand = prng.factory({
 				'state': opts.state,
 				'copy': opts.copy
 			});
 		}
 	} else {
 		rand = prng.factory({
 			'prng': opts.prng
 		});
 	}
 	setReadOnly( normal, 'NAME', 'randn' );
 
 	// If we are provided an "external" PRNG, we don't support getting or setting PRNG state, as we'd need to check for compatible state value types, etc, entailing considerable complexity.
 	if ( opts.prng ) {
 		setReadOnly( normal, 'seed', null );
 		setReadOnly( normal, 'seedLength', null );
 		setReadWriteAccessor( normal, 'state', constantFunction( null ), noop );
 		setReadOnly( normal, 'stateLength', null );
 		setReadOnly( normal, 'byteLength', null );
 		setReadOnly( normal, 'toJSON', constantFunction( null ) );
 	} else {
 		setReadOnlyAccessor( normal, 'seed', getSeed );
 		setReadOnlyAccessor( normal, 'seedLength', getSeedLength );
 		setReadWriteAccessor( normal, 'state', getState, setState );
 		setReadOnlyAccessor( normal, 'stateLength', getStateLength );
 		setReadOnlyAccessor( normal, 'byteLength', getStateSize );
 		setReadOnly( normal, 'toJSON', toJSON );
 	}
 	setReadOnly( normal, 'PRNG', rand.PRNG );
 	return normal;
 
 	/**
 	* Returns the PRNG seed.
 	*
 	* @private
 	* @returns {*} seed
 	*/
 	function getSeed() {
 		return rand.seed;
 	}
 
 	/**
 	* Returns the PRNG seed length.
 	*
 	* @private
 	* @returns {PositiveInteger} seed length
 	*/
 	function getSeedLength() {
 		return rand.seedLength;
 	}
 
 	/**
 	* Returns the PRNG state length.
 	*
 	* @private
 	* @returns {PositiveInteger} state length
 	*/
 	function getStateLength() {
 		return rand.stateLength;
 	}
 
 	/**
 	* Returns the PRNG state size (in bytes).
 	*
 	* @private
 	* @returns {PositiveInteger} state size (in bytes)
 	*/
 	function getStateSize() {
 		return rand.byteLength;
 	}
 
 	/**
 	* Returns the current pseudorandom number generator state.
 	*
 	* @private
 	* @returns {*} current state
 	*/
 	function getState() {
 		return rand.state;
 	}
 
 	/**
 	* Sets the pseudorandom number generator state.
 	*
 	* @private
 	* @param {*} s - generator state
 	* @throws {Error} must provide a valid state
 	*/
 	function setState( s ) {
 		rand.state = s;
 	}
 
 	/**
 	* Serializes the pseudorandom number generator as a JSON object.
 	*
 	* ## Notes
 	*
 	* -   `JSON.stringify()` implicitly calls this method when stringifying a PRNG.
 	*
 	* @private
 	* @returns {Object} JSON representation
 	*/
 	function toJSON() {
 		var out = {};
 		out.type = 'PRNG';
 		out.name = normal.NAME + '-' + rand.NAME;
 		out.state = typedarray2json( rand.state );
 		out.params = [];
 		return out;
 	}
 
 	/**
 	* Returns a pseudorandom number drawn from a standard normal distribution.
 	*
 	* @private
 	* @returns {number} pseudorandom number
 	*
 	* @example
 	* var v = normal();
 	* // returns <number>
 	*/
 	function normal() {
 		return rand();
 	}
 }
 
 
 // EXPORTS //
 
 module.exports = factory;