gistfile1.scala

/**
 * remove the first element satifying the predicate
 * @return an iterable minus the first element satisfying the predicate
 */
 def removeFirst(predicate: T => Boolean): Iterable[T] = {
   if (xs.isEmpty) xs
   else if (predicate(xs.head)) xs.drop(1)
   else xs.take(1) ++ xs.removeFirst(predicate)
 }
/**
 * replace the first element of the iterable with another element
 */
def replaceFirst(function: T => T): Iterable[T] = {
  if (xs.isEmpty) xs
  else xs.take(1).map(f(_)) ++ xs.drop(1)
}