From: skaller <skaller@users.sourceforge.net>
To: Nate Nystrom <nystrom@cs.cornell.edu>
Cc: caml-list@yquem.inria.fr, Andrew Myers <andru@cs.cornell.edu>
Subject: Re: [Caml-list] Possibility of Nested Classes and Nested Inheritance?
Date: 25 Dec 2004 11:26:49 +1100 [thread overview]
Message-ID: <1103934408.6201.215.camel@pelican.wigram> (raw)
In-Reply-To: <CFEDD357-55E4-11D9-9B74-000A958B604C@cs.cornell.edu>
On Sat, 2004-12-25 at 06:48, Nate Nystrom wrote:
> Using the traditional visitor pattern,
> you will have to parameterize the visitor class on every AST node class.
Given a term for expressions, and a map_expr function
which is a functional visitor, I can write:
let rec cfold x =
match map_expr cfold x with
| `Add (`Int a, `Int b) -> `Int (a + b)
| other -> other
The fact that this formulation admits any number of extra
variants without change is a problem! I could add
a new term `Sub for subtraction and forget to add
the code to fold subtraction of constants.
In fact I have done just that, it took several hours
to find the bug.
--
John Skaller, mailto:skaller@users.sf.net
voice: 061-2-9660-0850,
snail: PO BOX 401 Glebe NSW 2037 Australia
Checkout the Felix programming language http://felix.sf.net
next prev parent reply other threads:[~2004-12-25 0:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20041217184433.GA1036@balm.cs.cornell.edu>
2004-12-24 19:48 ` Nate Nystrom
2004-12-25 0:26 ` skaller [this message]
2004-12-25 10:59 ` Jacques Garrigue
2004-12-27 2:24 ` Jacques Garrigue
2004-12-16 14:59 Jørgen Hermanrud Fjeld
2004-12-16 21:50 ` [Caml-list] " John Prevost
2004-12-17 1:31 ` Jacques Garrigue
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1103934408.6201.215.camel@pelican.wigram \
--to=skaller@users.sourceforge.net \
--cc=andru@cs.cornell.edu \
--cc=caml-list@yquem.inria.fr \
--cc=nystrom@cs.cornell.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox