Let's make our first function. We want something like the following mathematical function\\
$f(x) = x * x$
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How could the haskell code look like?
\pause
Almost the same:
\begin{haskellcode}
f x = x * x
\end{haskellcode}
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GHCi...
\pause
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What is a possible type signature for this function?
\begin{haskellcode}
f :: Int -> Int
f x = x * x
\end{haskellcode}
So the function gets an Int and returns an Int. Don't get confused by "\verb|->|". Just think of it as a symbol for separating input and output.