Fact unitGI_out : {in [predC unitGI], invGI =1 id}.
Definition GI_comUnitRingMixin :=
ComUnitRingMixin mulGIr unitGIP unitGI_out.
Canonical GI_unitRingType := UnitRingType GI GI_comUnitRingMixin.
Canonical GI_comUnitRingType := [comUnitRingType of GI].

Lemma truncC_Cint (x : algC) :
x \in Cint -> x = (-1) ^+ (x < 0)%R * (truncC `|x|)%:R.