title: how to set variables interactively for ediff
body: <p>I'm using ediff mode, and I'd like to split the windows horizontally instead of the vertical default. The ediff manual says this can be done interactively.</p>
  
  <blockquote>
    <p>ediff-split-window-function</p>
    
    <p>Controls the way you want the window be split between file-A and
    file-B (and file-C, if applicable). It defaults to the vertical split
    (split-window-vertically, but you can set it to
    split-window-horizontally, if you so wish. Ediff also lets you switch
    from vertical to horizontal split and back interactively.</p>
    
    <p>Note that if Ediff detects that all the buffers it compares are
    displayed in separate frames, it assumes that the user wants them to
    be so displayed and stops splitting windows. Instead, it arranges for
    each buffer to be displayed in a separate frame. You can switch to the
    one-frame mode by hiding one of the buffers A/B/C.</p>
    
    <p>You can also swap the windows where buffers are displayed by typing ~</p>
  </blockquote>
  
  <p>I've tried using  M-x set-variable to set this variable to split-window-horiztonally, but that did not change the layout. I want to do this interactively, I know I can set it as default in .emacs but I dont want to do that at this stage.</p>