Definition other_beq a b :=
match a, b with
| ftwo_power_nat, ftwo_power_nat
| fforce_ptr, fforce_ptr
| fand, fand
| falign, falign
| ftyped_true, ftyped_true => true
| fnone t1, fnone t2
| fsome t1, fsome t2
| feq t1, feq t2 => typ_beq t1 t2
| _, _ => false
end
.

Lemma other_beq_sound : forall a b, other_beq a b = true -> a = b.