invert( quote( A >  5 ) )
  invert( quote( A >= 5 ) )
  invert( quote( A <  5 ) )
  invert( quote( A <= 5 ) )
  invert( quote( A == 5 ) )
  invert( quote( A != 5 ) )
  invert( quote( A %in% lettters[1:5] ) )
  invert( quote( A %!in% letters[1:5] ) )
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