Definition to_dirr  (B : {set gT}) (phi : 'CF(B)) (i : Iirr B) : dIirr B :=
('[phi, 'chi_i] < 0, i).
Definition of_irr (B : {set gT}) (i : dIirr B) : Iirr B := i.2.

Lemma cfdot_todirrE (phi: 'CF(G)) i (phi_i := dchi (to_dirr phi i)) :
'[phi, phi_i] *: phi_i = '[phi, 'chi_i] *: 'chi_i.