It is a great example, shows both howto and benefits. Thanks.
2009/11/14 Maurício CA
I have looked the concept of monoid and something related, but still, I do not know why we use it?
I don't know if it's a good example, but it's simple. This package I wrote uses reverse polish notation to write gtk2hs layout windows.
http://hackage.haskell.org/package/gtk2hs-rpn
Since the type for operators used in the stack is a Monoid instance, you can combine many of them to create new operators.
I believe you can think of monoids as things you can sequence to make new ones of the same type, but someone with better knowledge please say if this is actually a misleading idea.
Best, Maurício
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