という再帰データ型のジェネレータを作成しようとしていRowます。行は名前付きValのリストであり、 aValはアトミックBinまたはネストされたRowです。
これは私のコードです:
package com.dtci.data.anonymize.parquet
import java.nio.charset.StandardCharsets
import org.scalacheck.Gen
object TestApp extends App {
sealed trait Val
case class Bin(bytes: Array[Byte]) extends Val
object Bin {
def from_string(str: String): Bin = Bin(str.getBytes(StandardCharsets.UTF_8))
}
case class Row(flds: List[(String, Val)]) extends Val
val gen_bin = Gen.alphaStr.map(Bin.from_string)
val gen_field_name = Gen.alphaLowerStr
val gen_field = Gen.zip(gen_field_name, gen_val)
val gen_row = Gen.nonEmptyListOf(gen_field).map(Row.apply)
def gen_val: Gen[Val] = Gen.oneOf(gen_bin, gen_row)
gen_row.sample.get.flds.foreach( fld => println(s"${fld._1} --> ${fld._2}"))
}
次のスタック トレースでクラッシュします。
Exception in thread "main" java.lang.NullPointerException
at org.scalacheck.Gen.$anonfun$flatMap$2(Gen.scala:84)
at org.scalacheck.Gen$R.flatMap(Gen.scala:243)
at org.scalacheck.Gen$R.flatMap$(Gen.scala:240)
at org.scalacheck.Gen$R$$anon$3.flatMap(Gen.scala:228)
at org.scalacheck.Gen.$anonfun$flatMap$1(Gen.scala:84)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$5.doApply(Gen.scala:255)
at org.scalacheck.Gen$$anon$1.$anonfun$doApply$1(Gen.scala:110)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$1.doApply(Gen.scala:109)
at org.scalacheck.Gen.$anonfun$map$1(Gen.scala:79)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$5.doApply(Gen.scala:255)
at org.scalacheck.Gen.$anonfun$flatMap$2(Gen.scala:84)
at org.scalacheck.Gen$R.flatMap(Gen.scala:243)
at org.scalacheck.Gen$R.flatMap$(Gen.scala:240)
at org.scalacheck.Gen$R$$anon$3.flatMap(Gen.scala:228)
at org.scalacheck.Gen.$anonfun$flatMap$1(Gen.scala:84)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$5.doApply(Gen.scala:255)
at org.scalacheck.Gen$$anon$1.$anonfun$doApply$1(Gen.scala:110)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$1.doApply(Gen.scala:109)
at org.scalacheck.Gen$.$anonfun$sequence$2(Gen.scala:492)
at scala.collection.LinearSeqOps.foldLeft(LinearSeq.scala:168)
at scala.collection.LinearSeqOps.foldLeft$(LinearSeq.scala:164)
at scala.collection.immutable.List.foldLeft(List.scala:79)
at org.scalacheck.Gen$.$anonfun$sequence$1(Gen.scala:490)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$5.doApply(Gen.scala:255)
at org.scalacheck.Gen.$anonfun$map$1(Gen.scala:79)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$5.doApply(Gen.scala:255)
at org.scalacheck.Gen$$anon$1.$anonfun$doApply$1(Gen.scala:110)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$1.doApply(Gen.scala:109)
at org.scalacheck.Gen.$anonfun$flatMap$2(Gen.scala:84)
at org.scalacheck.Gen$R.flatMap(Gen.scala:243)
at org.scalacheck.Gen$R.flatMap$(Gen.scala:240)
at org.scalacheck.Gen$R$$anon$3.flatMap(Gen.scala:228)
at org.scalacheck.Gen.$anonfun$flatMap$1(Gen.scala:84)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$5.doApply(Gen.scala:255)
at org.scalacheck.Gen$.$anonfun$sized$1(Gen.scala:551)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$5.doApply(Gen.scala:255)
at org.scalacheck.Gen$$anon$1.$anonfun$doApply$1(Gen.scala:110)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$1.doApply(Gen.scala:109)
at org.scalacheck.Gen.$anonfun$map$1(Gen.scala:79)
at org.scalacheck.Gen$Parameters.useInitialSeed(Gen.scala:318)
at org.scalacheck.Gen$$anon$5.doApply(Gen.scala:255)
at org.scalacheck.Gen.sample(Gen.scala:154)
私のコードの何が問題なのですか? また、それを自分で診断するにはどうすればよかったでしょうか?
Gen.oneOf注意として、厳密でありGen.lzy、再帰構造が必要であるという発言を見てきました。しかし、コードgen_val内での定義をラップするGen.lzy(...)と、現在のヌル ポインター例外ではなく、スタック オーバーフローが発生します。