Missing word "that" in the sentence:

"One benefit of higher-order functions is they enable you to..."
                                          ^

Interpreter output, in scala 2.10.2, for the expression:
  scala> def first(x: Int) = (y: Int) => x + y

is
  first: (x: Int)Int => Int

not, as the book states:
  first: (x: Int)(Int) => Int