SQL & PL/SQL

Hi all,
I have a function which will take a collection (table of numbers) as a input argument.
Each id in the collection corresponds to a set of columns.I need to return a cursor which will contain the resultsets for all the ids in the collection.How do i do it.
what should the query be ?
say each id has three columns a,b,c to be returned.
I am given the collection of ids and am supposed to return a cursor which will have a,b,c columns for all the ids.
For individual ids , its straight forward
select a,b,c from sometable where id=input_id.
But how do i construct the cursor given a collection of ids?
Thanks in advance.