循环语句 #

for (i <- 1 to 5) println(i)

for i <- 1 to 5 do println(i)

for {
  i <- 1 to 3
} {
  println(i)
}

for i <- 1 to 5 do println(i)

for i <- 1 until 5 do println(i)

for i <- 1 to 10 by 2 do println(i)

for i <- 10 to 1 by -1 do println(i)

for i <- Range(1, 10, 2) do println(i)

val list = List(1, 2, 3, 4, 5)

for item <- list do println(item)

for item <- list if item > 2 do println(item)

val doubled = for i <- 1 to 5 yield i * 2
println(doubled)

val names = for name <- List("Alice", "Bob", "Charlie") yield name.toUpperCase
println(names)

val result = for i <- 1 to 5 yield
  val doubled = i * 2
  doubled

val result2 = for i <- 1 to 5 yield i * 2

case class Person(name: String, age: Int)

val people = List(
  Person("Alice", 25),
  Person("Bob", 17),
  Person("Charlie", 30)
)

val adultNames = for
  person <- people
  if person.age >= 18
yield person.name

for
  i <- 1 to 3
  j <- 1 to 3
do
  println(s"($i, $j)")

for i <- 1 to 3 do
  for j <- 1 to 3 do
    println(s"($i, $j)")

val pairs = for
  i <- 1 to 3
  j <- 1 to 3
yield (i, j)

println(pairs)

for i <- 1 to 10 if i % 2 == 0 do println(i)

for
  i <- 1 to 10
  if i % 2 == 0
  if i > 5
do
  println(i)

val evenSquares = for
  i <- 1 to 10
  if i % 2 == 0
yield i * i

for
  i <- 1 to 5
  squared = i * i
do
  println(s"$i squared is $squared")

for
  x <- 1 to 10
  y = x * x
  z = y * y
yield (x, y, z)

var i = 0
while i < 5 do
  println(i)
  i += 1

var i = 0
while (i < 5) {
  println(i)
  i += 1
}

var i = 0
do
  println(i)
  i += 1
while i < 5

@annotation.tailrec
def countdown(n: Int): Unit =
  if n > 0 then
    println(n)
    countdown(n - 1)

countdown(5)

def findFirstNegative(list: List[Int]): Int =
  for item <- list do
    if item < 0 then return item
  0

def findFirstNegative(list: List[Int]): Option[Int] =
  var result: Option[Int] = None
  var i = 0
  while i < list.length && result.isEmpty do
    if list(i) < 0 then result = Some(list(i))
    i += 1
  result

def findFirstNegative(list: List[Int]): Option[Int] =
  list.find(_ < 0)

val scores = Map("Alice" -> 90, "Bob" -> 85, "Charlie" -> 95)

for (name, score) <- scores do
  println(s"$name: $score")

val matrix = Array(
  Array(1, 2, 3),
  Array(4, 5, 6),
  Array(7, 8, 9)
)

for
  row <- matrix
  elem <- row
do
  println(elem)

import scala.io.Source

for
  line <- Source.fromFile("data.txt").getLines()
  if line.nonEmpty
do
  println(line)

val numbers = (1 to 100).toList

val results = for
  n <- numbers.par
  if n % 2 == 0
yield n * n

val doubled1 = for i <- 1 to 5 yield i * 2
val doubled2 = (1 to 5).map(_ * 2)

val result1 = for
  i <- 1 to 10
  if i % 2 == 0
yield i * i

val result2 = (1 to 10).filter(_ % 2 == 0).map(n => n * n)

val result1 = for
  i <- 1 to 3
  j <- 1 to 3
yield (i, j)

val result2 = (1 to 3).flatMap(i => (1 to 3).map(j => (i, j)))

val squares = for i <- 1 to 10 yield i * i

val names = for name <- people if name.length > 3 yield name

var sum = 0
for i <- 1 to 10 do sum += i

val sum2 = (1 to 10).sum

val result = list
  .filter(_ > 0)
  .map(_ * 2)
  .take(10)

@annotation.tailrec
def factorial(n: Int, acc: Int = 1): Int =
  if n <= 1 then acc
  else factorial(n - 1, n * acc)

for (i <- 1 to 5) {
  println(i)
}

for i <- 1 to 5 do println(i)

val result = for {
  i <- 1 to 5
  if i % 2 == 0
} yield i * 2

val result = for
  i <- 1 to 5
  if i % 2 == 0
yield i * 2