Goal:
  
  A : Type
  a : A
  x : A
  l : list A
  IHl : BinInt.Z.lt BinNums.Z0
          (BinInt.Z.add (BinInt.Z.of_nat #|l|) (BinNums.Zpos BinNums.xH))
        → Some a = nth_error (List.rev l ++ [a]) (#|l| - 0)
  cstr : BinInt.Z.le BinNums.Z0 (BinInt.Z.of_nat #|l|)
  ============================
   (BinInt.Z.add (BinInt.Z.of_nat #|l|) (BinNums.Zpos BinNums.xH) =
    BinInt.Z.max BinNums.Z0
      (BinInt.Z.sub
         (BinInt.Z.add (BinInt.Z.of_nat #|l|) (BinNums.Zpos BinNums.xH))
         BinNums.Z0))


DEBUG:Going to execute:
fun => <coq-core.plugins.zify::ITER@0>