+ /* If there is not enough slack at either end to perform a shift,
+ then we must extend the range so that there is. We must extend
+ by two half bin widths in order to preserve the EVEN condition
+ established above. Also, we extend on the end with the least
+ slack, in order to keep things as balanced as possible. */
+ if ( upper_slack > lower_slack && upper_slack <= half_bin_width)