# Is it possible to defining a scalar with CTensor?

I have a tensor (rank zero) or a scalar $$\phi$$ which defined as

DefTensor[\[Phi][], M]


on manifold $$M$$. After defining the metric, how can I use CTensor to rewrite $$\phi$$? For example, I have tried

\[Phi] = CTensor[\[Phi]0[r[]]];


(where $$\phi0$$ is already defined as a scalarFunction).

s = CTensor[\[Phi]0[r[]], {}]