[erlang-questions] How to get the line number of currentexecutable code?

[David Mercer]

Richard A. O'Keefe wrote:
>
> I have also dreamed of a
>   -pure([f/n,...]).
> directive, such as NU Prolog had.
> This would make a verifiable claim that the function(s) named would
> only call functions that are themselves pure, and a promise that if
> any exception would be raised in a call to such a function it would
> not matter which exception.

For those of us not well-versed in NU Prolog, what is the benefit of this?
Please advise.  Thank-you.

David