是否有可能匹配斯卡拉值的范围？
例如：
val t = 5
val m = t match {
0 until 10 => true
_ => false
}
m将是true如果t是0和10，但假之间否则。 这一点并不当然的工作，但有什么办法来实现类似的东西？
Answer 1:
后卫使用Range ：
val m = t match {
case x if 0 until 10 contains x => true
case _ => false
}
Answer 2:
您可以使用卫士：
val m = t match {
case x if (0 <= x && x < 10) => true
case _ => false
}
Answer 3:
这里有另一种使用范围来匹配：
val m = t match {
case x if ((0 to 10).contains(x)) => true
case _ => false
}
Answer 4:
随着这些定义：
trait Inspector[-C, -T] {
def contains(collection: C, value: T): Boolean
}
implicit def seqInspector[T, C <: SeqLike[Any, _]] = new Inspector[C, T]{
override def contains(collection: C, value: T): Boolean = collection.contains(value)
}
implicit def setInspector[T, C <: Set[T]] = new Inspector[C, T] {
override def contains(collection: C, value: T): Boolean = collection.contains(value)
}
implicit class MemberOps[T](t: T) {
def in[C](coll: C)(implicit inspector: Inspector[C, T]) =
inspector.contains(coll, t)
}
你可以做这样的检查：
2 in List(1, 2, 4) // true
2 in List("foo", 2) // true
2 in Set("foo", 2) // true
2 in Set(1, 3) // false
2 in Set("foo", "foo") // does not compile
2 in List("foo", "foo") // false (contains on a list is not the same as contains on a set)
2 in (0 to 10) // true
所以，你需要的代码如下：
val m = x in (0 to 10)
Answer 5:
另一种选择是将其实这添加到使用implicits的语言，我增加了对INT和范围内的两个变化
object ComparisonExt {
implicit class IntComparisonOps(private val x : Int) extends AnyVal {
def between(range: Range) = x >= range.head && x < range.last
def between(from: Int, to: Int) = x >= from && x < to
}
}
object CallSite {
import ComparisonExt._
val t = 5
if (t between(0 until 10)) println("matched")
if (!(20 between(0 until 10))) println("not matched")
if (t between(0, 10)) println("matched")
if (!(20 between(0, 10))) println("not matched")
}
文章来源: Can a range be matched in Scala?
