Boolean return prooblem scala

Question

嗨，我正试图只返回true或false，但我缺少某些东西

def filterOut[T](p: T => Boolean, as: List[T]): List[T] = {
  as.foldLeft(List[T]())((out, x) => 
                         if (p(x)) {x::out} else {out}
                        )}

其中p是谓词。你能帮我吗？

Answer 1

您是否需要使用foldLeft()？

def atLeastOne[T](p: T => Boolean, as: Seq[T]): Boolean =
  as.foldLeft(false)(_ || p(_))

或者您被允许更直接吗？

def atLeastOne[T](p: T => Boolean, as: Seq[T]): Boolean =
  as exists p

测试：

atLeastOne((x:Int) => x > 57, List(3,11,71,43,5))          //res0: Boolean = true
atLeastOne[Char]('w'.==, "abcdef")                         //res1: Boolean = false
atLeastOne[String](_.isEmpty, "this-and--that".split("-")) //res2: Boolean = true
atLeastOne[Float](_ < 1F, Vector())                        //res3: Boolean = false