function wrap( rand ) {
	var flg;
	var r;

	// Flag indicating whether to generate new normal random variates or return a cached normal random variate:
	flg = true;

	return randn;

	/**
	* Generates a standard normally distributed pseudorandom number.
	*
	* @private
	* @returns {number} pseudorandom number
	*
	* @example
	* var r = randn();
	* // returns <number>
	*/
	function randn() {
		var u1;
		var u2;
		var a;
		var b;
		if ( flg ) {
			// Note: if `u1` is `0`, the natural log blows up, so we keep trying until we get a non-zero rand. Rarely should we need more than one iteration.
			do {
				u1 = rand();
				u2 = rand();
			} while (
				u1 === 0.0
			);
			a = sqrt( -2.0 * ln(u1) );
			b = TWO_PI * u2;
			r = a * cos( b ); // cache for next call
			flg = false;
			return a * sin( b );
		}
		flg = true;
		return r;
	}
}
Returns a function for generating standard normally distributed pseudorandom numbers using the Box-Muller algorithm.

@private
@param {PRNG} rand - PRNG which returns standard uniformly distributed numbers
@returns {PRNG} PRNG