Definire un metodo iterativo su un oggetto:Metodo è coda ricorsiva quando definito nell'oggetto ma non sulla classe
object Recursive {
def recurse(maxDepth: Int = 10): Unit = {
if (maxDepth == 0) throw new Exception
recurse(maxDepth - 1)
}
}
dà:
scala> Recursive.recurse(10)
java.lang.Exception
at Recursive$.recurse(<console>:7)
at .<init>(<console>:7)
at .<clinit>(<console>)
at RequestResult$.<init>(<console>:9)
at RequestResult$.<clinit>(<console>)
at RequestResult$scala_repl_result(<console>)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at scala.tools.nsc.Interpreter$Request$$anonfun$loadAndRun$1$$anonfun$apply$17.apply(Interpreter.scala:988)
at scala.tools.nsc.Interpreter$Request$$anonfun$loadAndRun$1$$anonfun$apply$17.apply(Interpreter.scala:988)
at scala.util.control.Exception$Catch.apply(Exception.scal...
Ma definente su una classe:
class Recursive {
def recurse(maxDepth: Int = 10): Unit = {
if (maxDepth == 0) throw new Exception
recurse(maxDepth - 1)
}
}
fornisce:
scala> new Recursive recurse(10)
java.lang.Exception
at Recursive.recurse(<console>:7)
at Recursive.recurse(<console>:8)
at Recursive.recurse(<console>:8)
at Recursive.recurse(<console>:8)
at Recursive.recurse(<console>:8)
at Recursive.recurse(<console>:8)
at Recursive.recurse(<console>:8)
at Recursive.recurse(<console>:8)
at Recursive.recurse(<console>:8)
at Recursive.recurse(<console>:8)
at Recursive.recurse(<console>:8)
at .<init>(<console>:7)
at .<clinit>(<console>)
at RequestResult$.<init>(<console>:9)
at RequestResult$.<clinit>(<console>)
at RequestResult$scala_repl_result(<console>)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcc..
I metodi sono identici. Perché non è ricorsivo in coda se definito in una classe?
utilizzare sempre @tailrec per verificare l'intenzione – ron