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Date: Thu, 30 Jun 2005 10:34:59 -0400
From: Matthew Heaney <mheaney@on2.com>
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Subject: Re: How difficult is ada to learn?
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Date: 2005-06-30T14:34:59+00:00
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Gene wrote:
> 
> Most people who start with Borland Pascal miss the built-in set and
> string data types. Ada gets the same effects with packages, but the
> syntax is far less elegant and readable.

I haven't done any Pascal in a while, so I don't remember the syntax for 
set manipulation, but Ada 2005 will have a set container type.  It's an 
abstract data type, declared in a package in the normal way.  It 
supports union, intersection, etc.

If not having "built-in" syntax is a hardship, then you can always 
define array-based set operations yourself.  For example, suppose we 
have a set whose element type is Integer, then we can do this:

type Integer_Array is array (Positive range <>) of Integer;

function "+" (IA : Integer) return Integer_Sets.Set is
   S : Set;
begin
   for Indx in IA'Range loop
      S.Include (IA (Indx));
   end loop;

   return S;
end;

Now you can say:

declare
    S1 : Set := +(1, 2, 3);
    S2 : Set := +(2, 3, 4);
    S3 : Set := S1 or S2;
    S4 : Set := S3 and +(1, 3);
    S5 : Set := +(42, 43) or +(44, 45);
begin  ...;

That's not that inelegant.  Not much different from Pascal, as I recall...