From: pkk@spth.de   
      
   Further investigation shows that this was an intentional, but   
   undocumented change in flex in 2015 (flex 2.5.4 input() returns EOF at   
   the end of the file, flex 2.6.4 input() returns 0). However I still have   
   no idea why this change was made.   
      
   I guess the only portable way to handle the end of the file is to set a   
   flag in yywrap() and check it each time input() was called.   
      
   Philipp   
   [Returning EOF was a bug.  The lex input() always returned 0 at end of file.   
   -John]   
      
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