function iterator( options ) {
	var opts;
	var iter;
	var rand;
	var FLG;
	var i;

	if ( arguments.length > 0 ) {
		if ( !isObject( options ) ) {
			throw new TypeError( format( 'invalid argument. Options argument must be an object. Value: `%s`.', options ) );
		}
		opts = assign( {}, options );
		if ( hasOwnProp( opts, 'iter' ) ) {
			if ( !isNonNegativeInteger( opts.iter ) ) {
				throw new TypeError( format( 'invalid option. `%s` option must be a nonnegative integer. Option: `%s`.', 'iter', opts.iter ) );
			}
		} else {
			opts.iter = MAX_VALUE;
		}
		rand = rnorm( opts );
		if ( opts.prng === void 0 && opts.copy !== false ) {
			opts.state = rand.state; // cache a copy of the PRNG state
		}
	} else {
		rand = rnorm();
		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( 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;
	}
}
Returns an iterator for generating pseudorandom numbers drawn from a standard normal distribution using the Box-Muller transform.

@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} 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();

var r = iter.next().value;
// returns <number>

r = iter.next().value;
// returns <number>

r = iter.next().value;
// returns <number>

// ...