Scala and Python's pass

Question

I was wondering, is there an equivalent of python's pass expression? The idea is to write method signatures without implementations and compiling them just to type-check those signatures for some library prototyping. I was able to kind of simulate such behavior using this: ``` def pass[A]:A = {throw new Exception("pass"); (new Object()).asInstanceOf[A]} ``` now when i write: ``` def foo():Int = bar() def bar() = pass[Int] ``` it works(it typechecks but runtime explodes, which is fine), but my implementation doesn't feel right (for example the usage of java.lang.Object()). Is there better way to simulate such behavior?

Accepted Answer

In Scala 2.10, there is the `???` method in Predef.

```
scala> ???
scala.NotImplementedError: an implementation is missing
  at scala.Predef$.$qmark$qmark$qmark(Predef.scala:252)
  ...
```

In 2.9, you can define your own one like this:

```
def ???[A]:A = throw new Exception("not implemented")
```

If you use this version without an explicit type paramter, `A` will be inferred to be `Nothing`.

Scala and Python's pass

Solution

Problem