Earlier quoted context omitted.
How many of them fit idiomatically into the language you choose to use on the JVM?
Clojure does a good job of introducing new idioms specifically for Java support. From their docs: (doto (new java.util.HashMap) (.put "a" 1) (.put "b" 2)) (.. System (getProperties) (get "os.name"))
So, in other words, it doesn't fit into preexisting languages idiomatically. You want to introduce new idioms into Closure to make it integrate better with the JVM.
That's fine, but it also means that if you want to do a direct port of, say, Ruby or Python or Erlang, you'll have several rather large warts compared to new languages designed to run on the JVM and use the Java class libraries.