> With all due respect, that's just bullshit. First of all because there is no such thing as "true referential transparency", second because most techniques that are available in Haskell for dealing with side-effects are also available in Scala.
A referentially transparent expression is guaranteed not to have side effects. A Haskell function which doesn't advertise in its type that it may have side effects, by being in the IO monad, can be trusted to be referentially transparent. This cannot be said about OCaml or Scala functions.
Pardon me...are you saying you want something in the type signature of a scala function that guarantees said function will not do input output to files sockets etc...and does not make a call to random number generators and does not modify global vars...so basically all it does is operate solely on params passed to it...absolutely no side effects...is that what you are asking for? That would be awesome from a testability standpoint...
Yes! This is exactly what you get in Haskell, and it is awesome for a number of reasons. Check this out:
Yeah I know exactly what you mean in Haskell. Its just that in scala given the java inter-op there are a whole hunch of escape hatches that will always be there. I remember in the coursera exercises when you submitted code that used mutable vars...it would flag your code and deduct points. So essentially even if someone provided a purefn annotation...to actually enforce that, the compiler would have to scan each function and disbar i/o, calls to rng, calls to global vars... tall order.
Which coursera course? For Scala, or functional programming, or something else? Do you have a link to it?
There's only one so far: FP in Scala, run by Odersky himself.
> If you really think about it, type-classes are all about passing around a global vtable implicitly. If anything, Scala's implicits are a superset of Haskell's type-classes and allows for techniques that Haskell isn't capable of.
First, I'm not a Haskell expert, but from what I understand there are no vtable passed around nor attached to "objects" in Haskell.
Type-classes are used to find an implementation given an instance. Without extensions you cannot do this:
> lst :: Show a => [a]
> lst = [1, "hello"]
So Haskell isn't the slightest dynamic here.
If you really think about it, type-classes are all about passing around a global vtable implicitly. If anything, Scala's implicits are a superset of Haskell's type-classes and allows for techniques that Haskell isn't capable of.
We could debate all day about what's better. If you're going to make the case that Haskell's type-classes are easier to reason about, then I can make the case that a dynamic language beats Haskell on reasoning about it any day of the week. In the end it's all about tradeoffs.
> true referential transparency requires control over side effects, which is something neither OCaml or Scala are capable of, but Haskell is
With all due respect, that's just bullshit. First of all because there is no such thing as "true referential transparency", second because most techniques that are available in Haskell for dealing with side-effects are also available in Scala. As examples, Scala's library is filled with monadic types and the Play framework makes use of Iteratees for composing HTTP responses, something which makes Comet/WebSocket a peach to deal with.