inductive fpbu (h) (g) (G1) (L1) (T1): relation3 genv lenv term ≝
| fpbu_fqup: ∀G2,L2,T2. ⦃G1, L1, T1⦄ ⊃+ ⦃G2, L2, T2⦄ → fpbu h g G1 L1 T1 G2 L2 T2
| fpbu_cpxs: ∀T2. ⦃G1, L1⦄ ⊢ T1 ➡*[h, g] T2 → (T1 = T2 → ⊥) → fpbu h g G1 L1 T1 G1 L1 T2
inductive fpbu (h) (g) (G1) (L1) (T1): relation3 genv lenv term ≝
| fpbu_fqup: ∀G2,L2,T2. ⦃G1, L1, T1⦄ ⊃+ ⦃G2, L2, T2⦄ → fpbu h g G1 L1 T1 G2 L2 T2
| fpbu_cpxs: ∀T2. ⦃G1, L1⦄ ⊢ T1 ➡*[h, g] T2 → (T1 = T2 → ⊥) → fpbu h g G1 L1 T1 G1 L1 T2