fact: Definition rec_case := λ"rec" λ"left" λ"right" "rec" @ λ"n" (mℕ @ Int 0) @ ℤeq @ "n" @ ("left" @ Id) @ ("right" @ λ"f" "f" @ Id).
imports: Arith Omega ClassicalRealizability.Kbase ClassicalRealizability.Integers ClassicalRealizability.KBool