Say I have some scala code like this:

// outputs 1, 4, 9, 16, 25, 36, 49, 64, 81, 100
println( squares )

def squares = {
    val s = for ( count <- 1 to 10 ) yield { count * count }
    s.mkString(", ");
}

Why do I have to use the temporary val s? I tried this:

def squares = for ( count <- 1 to 10 ) yield { count * count }.mkString(", ")

That fails to compile with this error message:

error: value mkString is not a member of Int
   def squares = for ( count <- 1 to 10 ) yield { count * count }.mkString(", ")

Shouldn't mkString be called on the collection returned by the for loop?