I can't seem to find what it does anywhere. For example say you have a method such as
def SomeFunction(a: String): String ={
???
}
What do the triple question marks signify?
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3scala-lang.org/files/archive/nightly/docs/library/…– NikitaCommented Jul 8, 2015 at 20:00
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@ipoteka Thanks, tried searching in there and google before too but the question marks made it difficult to find. Makes sense though– ZeeCommented Jul 8, 2015 at 20:03
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2 Answers
??? is defined in Predef and simply throws a NotImplementedError:
def ??? : Nothing = throw new NotImplementedError
it has a return type of Nothing which is a sub-type of every type and can therefore be used in place of any return value.
While the answer given in https://stackoverflow.com/a/31302610/16372300 is technically accurate, it doesn't answer why you might come across ???, especially in tutorials and presentation. In the original question, SomeFunction is defined as a method that takes a single input of type String and returns a String. This is basically a stub, and allows you to continue coding using SomeFunction, but cannot run the code until you actually provide a definition that implements SomeFunction.
