[Haskell-cafe] Are there arithmetic composition of functions?

[Don Stewart]

.
>
> On a side note, if we consider typeclasses as predicates on types, then
(especially with the extensions enabled) the type system looks extremely
like a obfuscated logic programming language.With existential types it even
starts to look like a first-order thereom prover.
> At present we can easily express different flavors of conjunction, but
expressing disjunction is hard. And that's why the Prelude can cause
problems here.
>
>

See
http://www.cse.chalmers.se/~hallgren/Papers/wm01.html

It gets even more fun with GADTs and, particularly, type families, which
are explicitly designed with type level proofs in mind

-- Don
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