Exercise 4.1ish - Implementing Filter with Map

[Glendon Klassen]

Hi all,

I'm working through chapter 4 and have implemented filter like this:

def filter(f: A => Boolean): Option[A] = this map(f) match {
    case Some(true) => this
    case _ => None
  }

but the answer key has it like this:

def filter(f: A => Boolean): Option[A] = this match {
    case Some(a) if f(a) => this
    case _ => None
  }

Is there something inefficient/wrong about the way I've done it or is this just one of the possible implementations?

Thanks!

gjk

[pagoda_5b]

possibly your implementation will need to make one additional call after pattern matching... but I don't know enough about the internals to tell if there's some rewrite rule to optimize it away (I doubt so).

In any case I wouldn't worry too much, the result should be correct anyway

ivano