whileCallwP : (c :  @$\mathbb{N}$@ ) @$\rightarrow$@ Set
whileCallwP c = whileTestPwP {_} {_} c (@$\lambda$@ env s @$\rightarrow$@ loopPwP' (varn env) env refl (conv env s) ( @$\lambda$@ env s @$\rightarrow$@ vari env @$\equiv$@ c10 env )  )
  where
    conv : (env : Envc ) @$\rightarrow$@ (vari env @$\equiv$@ 0) @$\wedge$@ (varn env @$\equiv$@ c10 env) @$\rightarrow$@ varn env + vari env @$\equiv$@ c10 env
    conv e record { pi1 = refl ; pi2 = refl } = +zero