Free theorems for the dummies | Hackle's blog

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While the genius programmers excel on intuition, a simpler-minded one like myself needs more rigorous methods as safe fall-back. However, there is a misunderstanding that the rigorous methods are simply laborious and boring, bourne out of paranoia; that may be true of primitive forms such as unit testing (even which has rigorous forms); not the really good ones! My go-to example is "theorems for free": from functions with generics (or, parametric function), there is a recipe to derive theorems. It's mind-boggling, it's beautiful, and it's free. Well, it's not really easy if you go by the original paper by the great Philip Wadler, but I think I have an explanation for the dummies, so here we go.