On Fri, Apr 3, 2009 at 10:52 PM, Moritz Lenz <mor...@faui2k3.org> wrote:

> Xiao Yafeng wrote:
> > 1. Could I set multi-return type?like
> >                          sub test as (Int, Str) {...}
>
> "as" is coercion - so to what would it coerce? Int or Str? How could the
> compiler know? Or do you mean something like a tuple?
>

   as what Timothy S. Nelson say


>
> > 2. set is unordered collection of values´╝î subset is new type.  People are
> > apt to confuse the two concepts.
>
> Note that people never write "subset" in their code, the write things like
> sub f($x where { ... } )  and the  "where" constructs the subset type. I
> don' think that's
>

             I think subset can define a new type, I'm custom to set it at
head of code,
                            subset name_string of Str where {~~/^^name/};
             am I wrong?


>
> > 3. Could I define primary key for a bag variable?
>
> All items in a Bag are "primary keys", but there's no data additional
> data associated with it.
>

     I mean whether I can see Set as a table  and Bag as a table with a
unique constraint? like:
        subset test of Bag(test_name Str, test_ID Int, primary key(test_ID))

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