whileCallwP : (c :  ℕ ) → Set
whileCallwP c = whileTestPwP {_} {_} c (λ env s → loopPwP' (varn env) env refl (conv env s) ( λ env s → vari env ≡ c10 env )  )
  where
    conv : (env : Envc ) → (vari env ≡ 0) /\ (varn env ≡ c10 env) → varn env + vari env ≡ c10 env
    conv e record { pi1 = refl ; pi2 = refl } = +zero