Rename isIdentity to isFixedPoint

[bxt]

There's an example in lecture 5 typeclasses incarnations in the chapter Categorical FP:

def isIdentity[A: Eq](a: A)(f: A => A): Boolean = {
  implicitly[Eq[A]].eqv(a, f(a))
}

The function name isIdentity suggests that it returns wether f is the identity function. But I think it only checks wether a is a fixed point of f. So I would propose to rename it.

[pheymann]

Hi @bxt ,
thanks for the PR we appreciate it. Regarding your change, you are right. The function only shows that f is a fixpoint. We have no 'proof' that ∀ a : a == f(a).

Before we can merge, could you execute the following sbt command:

$> sbt "project typeclasses-incarnations-lecture" "fullCompile"

and commit the changed JavaScript presentation?

[bxt]

Hey @pheymann, sure, I ran the command and commited the changed JavaScript presentation.

[pheymann]

👍