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- Let's define something more complex. How about a tree?
- \pause
- \begin{haskellcode}
- data Tree = Leaf Char
- | Node Tree Int Tree
- \end{haskellcode}
- Uh... that looks mean. Let's examine this.\\
- \pause
- We have:
- \begin{itemizep}
- \item defined a data type \hinline{Tree}
- \item a constructor \hinline{Leaf} of type \hinline{Tree} with one arguments of type \hinline{Char}
- \item a constructor \hinline{Node} of type \hinline{Tree} with 3 arguments
- \begin{itemizep}
- \item \hinline{Tree}
- \item \hinline{Int}
- \item \hinline{Tree}
- \end{itemizep}
- \end{itemizep}
- \slidep
- That means: a \hinline{Tree} can either be a \hinline{Leaf} or an internal \hinline{Node} with two sub-trees. If we want to create a \hinline{Leaf}, we have to pass the constructor a \hinline{Char}. If we want to create a \hinline{Node}, we have to pass 3 arguments, in order: another \hinline{Tree}, an \hinline{Int} and yet another \hinline{Tree}.\\
- So we can save information in the leafs (\hinline{Char}) and in the internal nodes (\hinline{Int}).\\
- This is just an example. There are endless more ways of trees.
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