Re: Looking for generic hash function

[Stephen & Tammy House <house@ro.com>]

Robert Grandy wrote:
> 
> Hello,
> 
> I am looking for a function that will return a random-type integer based
> on a generic parameter. What I have in mind is:
> 
> generic
>   type data_type is private;
> function get_data_id return Integer;

You could try taking in one step further with:
generic
  type data_type is private;
  type id is (<>);
function data_id (d : data_type) return id;

function data_id (d : data_type) return id is
  type integers is array (integer range <>) of integer;
  local_d : constant data_type := d;
  --alias I integer array to same location as local_d, basically
begin
  return --normalize sum of all I into id'range
end data_id;

I don't remember all the syntax of alises, and I'd have to work out the
conversion into the id'range, but this should work for big or small
data_type structures.  Of course, if data_type'size < integer'size,
you'll need to have an alternate plan going.  You might make a local
integer type based upon min(data_type'size, standard.integer'size) to
avoid this problem.