I have spent much time looking for a functional language that can seamlessly access Java legacy code (Weka code). Autocompletion of imported Java class methods would be excellent. I will present my impressions, please correct me if I am wrong.
Yeti is very appealing to me because it is simple and ML-like, but I couldn't setup a good IDE for it. I don't know also if the language itself is already usable in real life.
Groovy, JRuby and Jython seem very mature, but are not really functional. Scala is mature but is OO also and at least on Netbeans (and Eclipse if I remember well) it is buggy.
"OCaML-Java" is OO also and doesn't come ready to use (3 or 4 separate projects). I suppose that in IDEs it would be even less ready to use.
Jaskell appears to be dead.
Clojure seems mature and works really well in Intellij IDEA (La Clojure plugin), but I am not sure I want to write more than 2 parens per line while coding.
SISC and ABCL I didn't try. I think there is no IDE support.
CAL (or Quark ... Blah ...) language leads to a SAP site and after that my patience searching for functional JVM languages ended.
There are similar questions but not comprehensive. For instance: Which Functional programming language offers best support in Eclipse?
Is some JVM functional language that is capable to call java classes directly missing? If Yeti had IDE support as Clojure has (in IDEA), it would be perfect to me.
Thanks
EDIT-----------------------------------
I could use Clojure+Scala in Intellij IDEA. Example of interoperability:
Scala code
package a
class ScalaMain {
def test = {
"testing!"
}
}
Clojure code
(import '(a ScalaMain)) ;'
(def scalainstance (new ScalaMain))
(print "printing: " (. scalainstance test))
Spectacular!
Scala + eclipse IDE (latest version) http://www.scala-ide.org/ seems to be getting better and better. Same for the IntellijIDEA plugin. There are lots of people/companies now developing with Scala... I don't think they all use Text Editors only.
I think that the most FP languages at the moment are Scala (multi-paradigm) and Clojure (pure functional) What is wrong with Scala being OO?
You can expect new languages comming such as Kotlin and Ceylon having functional features as well but they will also be OO, so I think your only choice now is between Scala and Clojure.
From your list you missing Fantom language. It also has Functional features, but I think it lacks IDE support (or atleast it is not updated to the latest versions)
UPDATE: There is now an eclipse-based IDE for the Fantom programming language that looks really nice. You can find it here: http://www.xored.com/products/f4/