Select from a REF CURSOR

This may be a dumb question, but I've never got my head round the strange TABLE(CAST(...)) syntax. I have a function which returns a REF CURSOR. What I'd like to do is to use this function in a SELECT statement. Something like:

    CREATE FUNCTION f(args) RETURNS SYS_REFCURSOR ...

    SELECT * FROM f(1,2,3);

Is this possible, and if so what syntax should I be using?

Thanks,
Paul.

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