Brzozowski, nice one!   
      
   Or this one:   
      
   boolean derivative   
   https://en.wikipedia.org/wiki/Reed%E2%80%93Muller_expansion   
      
   Am Mittwoch, 24. Januar 2018 01:34:46 UTC+1 schrieb Richard Fateman:   
   >    I was going to say  as an example, do we care what is   
   > the derivative of a string; then I remembered   
   > that I actually wrote a program to compute   
   > the Brzozowski derivative.  (look it up).   
      
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