Expansion using Protocols on Clojure data structures

Used in Pedestal route expansion and more detail in Pedestal Route tests

[:public "example.com"
   ["/" {:get home-page}
    ["/child-path" {:get trailing-slash}]]
   ["/user" {:get list-users
             :post add-user}
    ["/:user-id"
     ^:constraints {:user-id #"[0-9]+"}
     {:put update-user}
     [^:constraints {:view #"long|short"}
      {:get view-user}]]]

• Transform Readability : 3/5 lots of indirection layers, maybe due to depth of feature set
• Transform Safety : 2/5 not much obvious bad data shape checks
• Transform Versatility : 4/5 dispatching on Clojure types limits input variations but don't need many for web routing

Note: this is an example of a recursive terse DSL