Yes. That is effectively an impure function. It creates a side-effect: program execution continues somewhere other than the place to which the function is expected to return.

To make it a pure function, return an actual object that encapsulates the expected value from the function and a value indicating a possible error condition, like a Maybe Monad.

Yes. That is effectively an impure function. It creates a side-effect: program execution continues somewhere other than the place to which the function is expected to return.

To make it a pure function, return an actual object that encapsulates the expected value from the function and a value indicating a possible error condition, like a Maybe object or a Unit of Work object.