Which Functional programming language offers best support in Eclipse?

Question

As an exercise my team is looking at learning functional programming. One of the factors to choose a language is its support in Eclipse. Any language with Eclipse plug-in is fine but what language offers the best free plug-in?

Bonus question: the best online/book tutorial for this language.

Answer 1

I don't know if it is the best, but it is evolving and improving fast:

Scala IDE (up to Scala2.8.1RC1 right now)

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As for the best online Scala book:

Programming Scala (Creative Commons Attribution-Noncommercial)

But you will find other online sources in the SO question "List of freely available programming books".