Function: windmove-left

Select the window to the left of the current one.
With no prefix argument, or with prefix argument equal to zero,
"left" is relative to the position of point in the window; otherwise
it is relative to the top edge (for positive ARG) or the bottom edge
(for negative ARG) of the current window.
If no window is at the desired location, an error is signaled. (fn &optional ARG)