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;
	}
Generates a standard normally distributed pseudorandom number.

@private
@returns {number} pseudorandom number

@example
var r = randn();
// returns <number>