So why did we just bother so long with explaining currying? It's because it's very important for \emph{function composition}. Which again is also one of the fundamental concepts of functional programming.
\vspace{\baselineskip}
\\
From maths we already know that:\\
$(g \circ f)(x) = g(f(x))$
\vspace{\baselineskip}
\\
\pause
And that's basically it. We do the same in haskell, it looks like this:
\begin{haskellcode}
composedFunction x = (f . g) x

-- same as above... everything on the right side of $
-- is evaluated first
composedFunction x = f . g $ x

-- and same again, remember that 'f x ='
-- is just syntax sugar
-- omitting the x here is also called eta reduction
composedFunction = f . g
\end{haskellcode}