title: Lua, Advancing to the next letter of the alphabet
body: <p>I am very surprised that I did not find this explicitly answered here in StackOverflow, or on the <a href="http://www.lua.org/" rel="nofollow">Lua.org</a> Website</p>
  
  <p>If </p>
  
  <ul>
  <li>My Lua variable contains a single letter, and</li>
  <li>I want the next letter in the alphabet</li>
  </ul>
  
  <p>Then, how do I manipulate that variable to change from, say, "J" to "K" ?</p>
  
  <p>I looked at <a href="http://www.lua.org/pil/20.html" rel="nofollow">The String Library</a> in the <a href="http://www.lua.org/" rel="nofollow">Lua.Org</a> website, and didn't see the word "alphabet" on any of the pages there</p>
  
  <p>e.g.</p>
  
  <pre><code> --------------------------------------------------
   --                                              --
   --    Func Name: Alphabetic_Advance_By_1        --
   --                                              --
   --    On Entry:  The_Letter contains one        --
   --               character. It must be a        --
   --               letter in the alphabet.        --
   --                                              --
   --    On Exit:   The caller receives the        --
   --               next letter                    --
   --                                              --
   --               e.g.,                          --
   --                                              --
   --               A will return B                --
   --               B will return C                --
   --               C will return D                --
   --                                              --
   --               X will return Y                --
   --               Y will return Z                --
   --               Z will return A                --
   --                                              --
   --                                              --
   --                                              --
   --------------------------------------------------
  
  
  
   function Alphabetic_Advance_By_1(The_Letter)
  
   local Temp_Letter
  
   Temp_Letter = string.upper(The_Letter)
  
   -- okay, what goes here ???
  
  
   return(The_Answer)
  
   end
  </code></pre>