DEPRECATED: Purescript v0.15.0 now provides typelevel integers with compiler solved typeclasses, so there is no need anymore to use symbol-based arithmetic.
Arithmetic at the typelevel using symbols.
add ∷ ∀ augend addend sum carry result. Add augend addend carry sum ⇒ Cons carry sum result ⇒ Proxy augend → Proxy addend → Proxy result add _ _ = Proxy result ∷ Proxy "0579" result = add (term ∷ _ "123") (term ∷ _ "456")