From: "Maciek Godek" <pstrychuj@gmail.com>
To: guile-user@gnu.org
Subject: References/locations
Date: Fri, 8 Aug 2008 03:50:33 +0200 [thread overview]
Message-ID: <e2ceda030808071850uc1640e6kf4ffc33699143fd2@mail.gmail.com> (raw)
Hi,
it's me again, asking silly questions.
This time I would like to know if there's
a simple way to store a reference to
a variable in another variable -- say,
an element of vector or hash table.
I imagine this could look like this:
(define v #(1 2 3))
(define v1 (vector-location v 1))
v1
: 2
(set! v1 10)
v
: #(1 10 3)
I've tried to do it using a "procedure with
setter", but the problem is that set! doesn't
evaluate its first argument (as long as it's a
symbol), so I'd have to wrap everything
up in macros to obtain:
(set! (vector-location v 1) 10)
Besides I think that the names "hash-ref"
and "vector-ref" are confusing, since they
don't return references, but values (therefore
the names like "vector-get" or "hash-get" would
be more apropreate)
I also wonder if there's any point for allowing
locations to any sorts of variables (similar to
pointers in C or pointers to C++), that is,
(define x 10)
(define y (location x))
(set! y 20)
x
: 20
I expect that this idea isn't new in the world of
lisp, but I didn't find any discussion on the web.
There are certainly some issues related with locations:
- they require special behavior of set! and define:
(set! y 20) could work in two different ways,
depending on whether y is a location or not
- what about "locations of locations"?
- how would it affect performance?
- what about multiple threads?
Regards
M.
next reply other threads:[~2008-08-08 1:50 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-08 1:50 Maciek Godek [this message]
2008-08-10 7:51 ` References/locations Stephen Compall
2008-08-15 9:35 ` References/locations Maciek Godek
[not found] ` <e2ceda030808141732r524fc0cehb8ae7c6007550ea6@mail.gmail.com>
[not found] ` <m2wsihltfv.fsf@member.fsf.org>
[not found] ` <e2ceda030808200441q52d9858bv63323055e0f6308a@mail.gmail.com>
2008-08-21 5:05 ` References/locations Stephen Compall
[not found] <cmu-lmtpd-5833-1218211546-4@mail-imap1.uio.no>
2008-08-08 18:34 ` References/locations Kjetil S. Matheussen
2008-08-10 23:00 ` References/locations Maciek Godek
2008-08-15 10:14 ` References/locations Maciek Godek
2008-08-15 13:55 ` References/locations Clinton Ebadi
2008-08-18 8:09 ` References/locations Maciek Godek
2008-08-18 16:15 ` References/locations Clinton Ebadi
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