It sounds like a stupid question. However, can closed line-integrals be defined for one-dimensional real valued functions? To add a little substance to the question. In two dimensions it makes total sense to write
\begin{align} \oint_C ...ds \end{align}
for closed paths. The use of this notation makes also sense for contour-integrals in the context of one-dimensional complex-valued functions, since complex numbers can be interpreted as two-dimensional fields.
What about the pure one-dimensional real-valued case? Are there examples?