Section cube_colouring.
Definition cube := 'I_6.
Canonical cube_eqType := Eval hnf in [eqType of cube].
Canonical cube_choiceType := Eval hnf in [choiceType of cube].
Canonical cube_countType := Eval hnf in [countType of cube].
Canonical cube_finType := Eval hnf in [finType of cube].
Canonical cube_subType := Eval hnf in [subType of cube].
Canonical cube_subCountType := Eval hnf in [subCountType of cube].
Canonical cube_subFinType := Eval hnf in [subFinType of cube].
Definition mkFcube i : cube := Sub (i %% 6) (ltn_mod i 6).
Definition F0 := mkFcube 0.
Definition F1 := mkFcube 1.
Definition F2 := mkFcube 2.
Definition F3 := mkFcube 3.
Definition F4 := mkFcube 4.
Definition F5 := mkFcube 5.
(* axial symetries*)
Definition S05 := [:: F0; F4; F3; F2; F1; F5].
Definition S05f (sc : cube) : cube := tnth [tuple of S05] sc.
Definition S14 := [:: F5; F1; F3; F2; F4; F0].
Definition S14f (sc : cube) : cube := tnth [tuple of S14] sc.
Definition S23 := [:: F5; F4; F2; F3; F1; F0].
Definition S23f (sc : cube) : cube := tnth [tuple of S23] sc.
(* rotations 90 *)
Definition R05 := [:: F0; F2; F4; F1; F3; F5].
Definition R05f (sc : cube) : cube := tnth [tuple of R05] sc.
Definition R50 := [:: F0; F3; F1; F4; F2; F5].
Definition R50f (sc : cube) : cube := tnth  [tuple of R50] sc.
Definition R14 := [:: F3; F1; F0; F5; F4; F2].
Definition R14f (sc : cube) : cube := tnth [tuple of R14] sc.
Definition R41 := [:: F2; F1; F5; F0; F4; F3].
Definition R41f (sc : cube) : cube := tnth [tuple of R41] sc.
Definition R23 := [:: F1; F5; F2; F3; F0; F4].
Definition R23f (sc : cube) : cube := tnth [tuple of R23] sc.
Definition R32 := [:: F4; F0; F2; F3; F5; F1].
Definition R32f (sc : cube) : cube := tnth [tuple of R32] sc.
(* rotations 120 *)
Definition R024 := [:: F2; F5; F4; F1; F0; F3].
Definition R024f (sc : cube) : cube := tnth [tuple of R024] sc.
Definition R042 := [:: F4; F3; F0; F5; F2; F1].
Definition R042f (sc : cube) : cube := tnth [tuple of R042] sc.
Definition R012 := [:: F1; F2; F0; F5; F3; F4].
Definition R012f (sc : cube) : cube := tnth [tuple of R012] sc.
Definition R021 := [:: F2; F0; F1; F4; F5; F3].
Definition R021f (sc : cube) : cube := tnth [tuple of R021] sc.
Definition R031 := [:: F3; F0; F4; F1; F5; F2].
Definition R031f (sc : cube) : cube := tnth [tuple of R031] sc.
Definition R013 := [:: F1; F3; F5; F0; F2; F4].
Definition R013f (sc : cube) : cube := tnth [tuple of R013] sc.
Definition R043 := [:: F4; F2; F5; F0; F3; F1].
Definition R043f (sc : cube) : cube := tnth [tuple of R043] sc.
Definition R034 := [:: F3; F5; F1; F4; F0; F2].
Definition R034f (sc : cube) : cube := tnth [tuple of R034] sc.
(* last symmetries*)
Definition S1 := [:: F5; F2; F1; F4; F3; F0].
Definition S1f (sc : cube) : cube := tnth [tuple of S1] sc.
Definition S2 := [::  F5; F3; F4; F1; F2; F0].
Definition S2f (sc : cube) : cube := tnth [tuple of S2] sc.
Definition S3 := [::  F1; F0; F3; F2; F5; F4].
Definition S3f  (sc : cube) : cube := tnth [tuple of S3] sc.
Definition S4 := [:: F4; F5; F3; F2; F0; F1].
Definition S4f  (sc : cube) : cube := tnth [tuple of S4] sc.
Definition S5 := [::  F2; F4; F0; F5; F1; F3].
Definition S5f  (sc : cube) : cube := tnth [tuple of S5] sc.
Definition S6 := [::F3; F4; F5; F0; F1; F2].
Definition S6f  (sc : cube) : cube := tnth [tuple of S6] sc.
Definition sop (p : {perm cube}) : seq cube := fgraph (val p).
Definition ecubes : seq cube := [:: F0; F1; F2; F3; F4; F5].
Definition indir_iso3l := map (mulg s0) dir_iso3l.
Definition iso3l := dir_iso3l ++ indir_iso3l.
Definition seq_iso3_L := map sop iso3l.
Ltac iso_tac :=
let a := fresh "a" in apply/permP => a;
apply/eqP; rewrite !permM !permE; case: a; do 6?case.
Ltac inv_tac :=
apply: esym (etrans _ (mul1g _)); apply: canRL (mulgK _) _; iso_tac.
Definition is_iso3b p :=  (p * s0 == s0 * p).
Definition iso3 := [set p | is_iso3b p].

Lemma is_iso3P : forall p, reflect (is_iso3 p) (p \in iso3).