Another lovely example of type class morphisms
I read Max Rabkin’s recent post Beautiful folding with great excitement. He shows how to make combine multiple folds over the same list into a single pass, which can then drastically reduce memory requirements of a lazy functional program. Max’s trick is giving folds a data representation and a way to combine representations that corresponds to combining the folds.
Peeking out from behind Max’s definitions is a lovely pattern I’ve been noticing more and more over the last couple of years, namely type class morphisms.
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