The Functional Pearls series, of which you are probably aware, seems to be full of idiomatic and brilliant Haskell techniques. It's not an application but it's

The Functional Pearls series, of which you are probably aware, seems to be full of idiomatic and brilliant Haskell techniques. It's not an application but it's a flowering of expression, of a sort... https://wiki.haskell.org/Research_papers/Functional_pearls https://wiki.haskell.org/Research_papers/Functional_pearls