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From: fjh@cs.mu.oz.au (Fergus Henderson)
Subject: Re: Ultimate Language feature list
Date: 1998/05/15
Message-ID: <6jgivo$p18$1@mulga.cs.mu.OZ.AU>#1/1
X-Deja-AN: 353421475
References: <6jcjqq$jl4$1@nnrp1.dejanews.com>
Organization: Computer Science, The University of Melbourne
Newsgroups: comp.lang.ada,comp.lang.eiffel,comp.lang.sather
Date: 1998-05-15T00:00:00+00:00
List-Id: <comp.lang.ada>


In comp.lang.ada and comp.lang.eiffel,
adam@irvine.com writes:

 >Well, as long as we're talking about what language features we want,
 >here's one I've always wanted: The ability to deal with sequences of
 >objects.  I don't mean a list of objects where you have to create an
 >array or linked list in memory that contains all the objects; I mean
 >the ability to write code that talks about sequences of objects even
 >though the program only generates one at a time.  So I'd like to be
 >able to write a function like this:
 >
 >        -- Integer_List is a "traditional" linked list of integers
 >    function Nonzero_Elements_Of (List : Integer_List)
 >                 return sequence of Integer is
 >    begin
 >        List_P := List;
 >        while List_P /= null loop
 >            if List_P.Data /= 0 then
 >                return List_P.Data;
 >                    -- Note: this RETURN would return one integer but
 >                    -- would NOT terminate the function; eventually the
 >                    -- caller would return to this point in the function
 >                    -- to get more
 >            end if;
 >            List_P := List_P.Next;
 >        end loop;
 >    end;

I think you just reinvented Sather's `iterator' language construct.
Of course, some of the syntactic details are different, e.g. if I recall
correctly, this sort of iterator `return' is spelt `yield' in Sather.
But the basic concept is pretty much the same.

 >Well, I can dream.

You can do better than dream -- the Sather compiler is freely available,
so you can download it and try it out! ;-)

--
Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh@128.250.37.3        |     -- the last words of T. S. Garp.