[ryanartecona]

I'll add: if all this seems too opaque to jump into at once (and especially if you're unfamiliar with Haskell or other FP languages), don't give up on FP!

A "functional" language is not always a "pure" language, and a "pure functional" language certainly does not always have dependent types. These concepts build on each other.

A great intro to FP is "Programming in Standard ML". Concise, precise, and very approachable. SML is functional, but not pure nor dependently-typed (though purity is encouraged). http://www.cs.cmu.edu/~rwh/smlbook/book.pdf

Haskell is like SML with enforced purity, a different module/typeclass system, and default laziness. LYAH is the best intro. http://learnyouahaskell.com/

Idris is aimed primarily at those already familiar with Haskell, so don't be discouraged if the online REPL feels too foreign!