CODEWITHSUNDEEP
scala
jack huang
jack huang

Reputation: 77

confusing by scala replaceFirst

scala > val a = (x:Int)=>x+1
  res0: Int => Int = <function1>
scala > val b = a.getClass
  b: Class[_ <: Int => Int] = class $anonfun$1
scala > b.getName.replaceFirst("^.*\\.", "") + ".class"
  //Why there is a prefix '$read$'
  res2: String = $read$$anonfun$1.class

I'm confusing about the res2. I think the res2 should be '$anonfun$1.class'.

Upvotes: 2

Views: 121

Answers (1)

Alexey Romanov
Alexey Romanov

Reputation: 170825

This one was fun.

scala> val a = ((x: Int) => x).getClass.getName
a: String = $anonfun$1

scala> a == "$anonfun$1"
res2: Boolean = false

Wait, what?

scala> a.getBytes.map(_.toChar)
res3: Array[Char] = Array($, l, i, n, e, 4, ., $, r, e, a, d, $, $, i, w, $, $, i, w, $, $, a, n, o, n, f, u, n, $, 1)

So the name of the class is actually $line4.$read$$iw$$iw$$anonfun$1, not $anonfun$1. But why does Scala REPL print it like this? All executable Scala code must be inside a class, trait, or object definition. So when you enter a line in REPL which isn't, it gets wrapped inside an object. And apparently when printing an answer, REPL suppresses anything which looks like part of this object's generated name, even if it isn't where it comes from:

scala> "a$$iw$$b"
res7: String = a$$b

And $line4.$read$ qualifies for this suppression, but $read$ by itself doesn't.

Upvotes: 5

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