Hi Lars:

very good to know.
I put it into our related work directory.

-- Karl

>From lth@ccs.neu.edu Fri Sep 24 21:51:26 1999
>To: dougo@ccs.neu.edu, lieber@ccs.neu.edu, johan@ccs.neu.edu
>Subject: Algebraic DT / visitor-style programming in C++
>From: Lars Thomas Hansen <lth@ccs.neu.edu>
>
>
>This just in; I don't know anything more about it than it says but
>the comment about visitor-style programming in C++ caught my eye and
>so naturally I thought of you three.
>
>--lars
>
>From: George Nelan <nelan@home.com>
>Subject: ANN. Free C++ Algebraic Types
>Newsgroups: comp.lang.functional
>Date: Thu, 23 Sep 1999 02:01:47 GMT
>Organization: @Home Network
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>
>Not to peg the hype-o-meter, but app 1.0 is available.
>
>'App' is a preprocessor for C++ that accepts as input arbitrary
>C++ code that may contain embedded constructs for specifying
>algebraic data types and associated pattern matching operations,
>and produces as output the same code with all such constructs
>translated to normal C++.  What app essentially does is provide
>for C++ pretty much the same capabilities that functional
>languages have regarding algebraic types.  In a sense app can be
>viewed as bringing C++ closer to the functional programming world,
>although perhaps just as well app can be viewed as directly
>supporting certain kinds of visitor-style patterns in C++, insofar
>as algebraic types can be viewed as supporting such patterns.
>
>App is free software distributed under the terms of the GPL/LGPL.
>This software was developed on a W95 Intel platform using MS VC++
>5.0, and is initially targeted for similar platforms, though it
>should be easy enough to retarget for most any platform supporting
>a relatively modern C++ compiler.  The source code is not -- or at
>least should not be -- MS specific.  Substantial portions of app
>are written in itself.  You can download the software and browse
>the documentation at:
>
>	http://www.primenet.com/~georgen/app.html
>
>Here's a short example; function foo() produces "Y:{42}".
>
>$base I(int x) {
>  bool print(ostream& os) {
>    os << x();
>    return true;
>  }
>};
>
>$data W<class A> $forward;
>$data X<class A> = Y(A a) | Z(W<A> a);
>$data W<class A> = V(X<A> a);
>
>void foo() {
>  $match (V<I>(Y<I>(42))) {
>    (V<I>(y)) => {cout << y << endl;}
>  }
>}
>
>-- 
>George Nelan
>mailto:nelan@home.com
>
>PS.  Yes, I know that this is comp.lang.functional.
>