Search code examples
scalaunit-type

Can someone explain what is going on here?

Here's the code:

scala> def foo(bar: Unit => String) = {bar}
foo: (bar: (Unit) => String)(Unit) => String

scala> foo(a => a.toString)
res0: (Unit) => String = <function1>

I am guessing a is of type Unit, but isn't Unit an object? Is the Unit class hidden?

Solution

  • Unit is an AnyVal, like Int. Its sole member is a literal, written as (). For example:

    scala> def foo(bar: Unit => String) = {bar}
foo: (bar: Unit => String)Unit => String

scala> foo(a => a.toString)
res0: Unit => String = <function1>

scala> res0(())
res1: String = ()