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scalascala-repl

Why my function on Scala REPL is print as 'Lambda'?

I created this function on Scala REPL

scala> val multiDouble = (input :Double) =>
 |      {
 |          val toMulti = 2;
 |          toMulti * input 
 |      }: Double

And the output is val multiDouble: Double => Double = Lambda$1351/1709493124@7b44bfb8

For what I've studied it should be val multiDouble: Double => Double = <function01>

I don't understand why Scala REPL prints Lambda$1351/1709493124@7b44bfb8 and not <function01>.

Solution

  • In Scala 2.11- functions are printed as <function01>, in Scala 2.12+ they are printed as Lambda$.../...@...

    2.12 lambdas have different toString https://github.com/scala/scala-dev/issues/67

    @retronym:

    It is unavoidable if we use LambdaMetaFactory, which doesn't expose a way to provide an implementation of toString. (Default methods in interfaces themselves can't override methods in Object, either).

    We could provide ScalaLambdaMetafactory to generate precisely what we want, but the risk is that we will forgo current or future optimizations in HotSpot targetting LMF.

    Scala 2.12.0: output of assigning a function literal to a value

    datatype of anonymous function vs named function in scala

    https://contributors.scala-lang.org/t/functionns-tostring-should-show-the-types/2572