fact: Fixpoint PsubX (i':positive) (P:Pol) : Pol := match P with | Pc c => PX (--P') i' P | Pinj j Q' => match j with | xH => PX (--P') i' Q' | xO j => PX (--P') i' (Pinj (Pos.pred_double j) Q') | xI j => PX (--P') i' (Pinj (xO j) Q') end | PX P i Q' => match Z.pos_sub i i' with | Zpos k => mkPX (Pop (PX P k P0) P') i' Q' | Z0 => mkPX (Pop P P') i Q' | Zneg k => mkPX (PsubX k P) i Q' end end.
imports: Setoid Morphisms BinList BinPos BinNat BinInt Ring_theory