Pass where clause to a function

Hi all,

Is it possible to create a view or foreign table that will do something
like this

select * from table_x
where x_id = 10;

passing the where "x_id = 10" to a function

sorta like this

select * from api_function('x = 10')

or

select * from api_function(10)

passing the result set back to the original select....

Thanks