\begin{definition}[Definition:Convolution Integral/Cross-Correlation]
Let $f$ and $g$ be real functions which are integrable.
The '''cross-correlation''' of $f$ and $g$ is defined as:
:$\ds \map f t \star \map g t := \int_{-\infty}^\infty \map f u \map g {t + u} \rd u$
\end{definition}