[DrJokepu]

I agree that immutability is very useful, but you don't really need any kind of FP to use immutability, do you?

[braythwayt]

If your data is immutable, in what sense is your code not 'Functional Programming?'

"It's OO, and it can't be both OO and FP."

Hmmm.

[33degrees]

I was going to say the same thing; it's certainly possible to write immutable object oriented code

[norswap]

Indeed, it's more of a pattern.