title: alt-key binds in Vim: <A-D> won't work but <A-S-D> does
body: <p>I am binding yankstack to these keys: </p>
  
  <p>(note the <code>^[</code> here are the raw  char typed in with ctrl+v)</p>
  
  <pre><code>set &lt;A-D&gt;=^[d                                      
  set &lt;A-S-D&gt;=^[D                                    
  nmap &lt;A-D&gt; &lt;Plug&gt;yankstack_substitute_older_paste  
  nmap &lt;A-S-D&gt; &lt;Plug&gt;yankstack_substitute_newer_paste
  </code></pre>
  
  <p>The <code>&lt;A-S-D&gt;</code> is properly interpreted, but the <code>&lt;A-D&gt;</code> is not.</p>
  
  <p>Curiously, if I type <code>:set &lt;A-D&gt;</code>, I get back</p>
  
  <pre><code>     &lt;Ä&gt;        ^[D                    
  </code></pre>
  
  <p>So somehow it seems vim is thinking alt+d is equivalent to something that is not being sent by my terminal when I type Alt+D.</p>
  
  <p>I had to grab another of the high-F keys (the set of which i am going to run out of eventually) to get it working: </p>
  
  <pre><code>set &lt;F26&gt;=^[d                                      
  set &lt;A-S-D&gt;=^[D                                    
  nmap &lt;F26&gt; &lt;Plug&gt;yankstack_substitute_older_paste  
  nmap &lt;A-S-D&gt; &lt;Plug&gt;yankstack_substitute_newer_paste
  </code></pre>
  
  <p>Anyone know what this is all about?</p>