puzzle-seq-nil

main.scala

package example

object Hello {
  def main(_args: Array[String]): Unit = {
    check("1")
    check("1,2")
  }

  def check(s: String) = {
    val integers = s.split(",")
    val res1 = lengthIsEqualToOne_1(integers)
    val res2 = lengthIsEqualToOne_2(integers)
    println(s"${s} res1=$res1, res2=$res2")
  }

  def lengthIsEqualToOne_1(l: Seq[String]): Boolean = {
    l match {
      case head :: Nil => true
      case any => false
    }
  }

  def lengthIsEqualToOne_2(l: Seq[String]): Boolean = {
    l.length == 1
  }
}

main_test.scala

package example

import org.scalatest.funsuite._

class HelloSpec extends AnyFunSuite {
  test("Seq() lengthIsEqualToOne_1 == false") {
    assert(!Hello.lengthIsEqualToOne_1(Seq()))
  }

  test("Seq(1) lengthIsEqualToOne_1 == true") {
    assert(Hello.lengthIsEqualToOne_1(Seq("1")))
  }

  test("Seq(1, 2) lengthIsEqualToOne_1 == false") {
    assert(!Hello.lengthIsEqualToOne_1(Seq("1", "2")))
  }
}

scala-puzzle-seq-nil.txt

テストは通るが、`1 res1=true` にならない

```
sbt:Hello> test
[info] Done compiling.
[info] HelloSpec:
[info] - Seq() lengthIsEqualToOne_1 == false
[info] - Seq(1) lengthIsEqualToOne_1 == true
[info] - Seq(1, 2) lengthIsEqualToOne_1 == false
[info] Run completed in 243 milliseconds.
[info] Total number of tests run: 3
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 3, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[success] Total time: 2 s, completed 2023/05/21 1:26:23

sbt:Hello> run
[info] Running example.Hello 
1 res1=false, res2=true
1,2 res1=false, res2=false
[success] Total time: 0 s, completed 2023/05/21 1:26:25
```