From: David Kastrup <dak@gnu.org>
To: guile-devel@gnu.org
Subject: Re: Guile: What's wrong with this?
Date: Wed, 04 Jan 2012 10:41:33 +0100 [thread overview]
Message-ID: <8762grkdo2.fsf@fencepost.gnu.org> (raw)
In-Reply-To: 1325646278.7597.YahooMailNeo@web37902.mail.mud.yahoo.com
Mike Gran <spk121@yahoo.com> writes:
>> In many systems it is desirable for constants (i.e. the values of literal
>> expressions) to reside in read-only-memory. To express this, it is
>> convenient to imagine that every object that denotes locations is
>> associated with a flag telling whether that object is mutable or immutable.
>> In such systems literal constants and the strings returned by
>> `symbol->string' are immutable objects, while all objects created by
>> the other procedures listed in this report are mutable. It is an error
>> to attempt to store a new value into a location that is denoted by an
>> immutable object.
>>
>> In Guile this has been the case since commit
>> 190d4b0d93599e5b58e773dc6375054c3a6e3dbf.
>>
>> The reason for this is that Guile’s compiler tries hard to avoid
>> duplicating constants in the output bytecode. Thus, modifying a
>> constant would actually change all other occurrences of that constant in
>> the code, making it a non-constant. ;-)
>
> This is a terrible example of the RnRS promoting some strange idea of
> mathematical purity over being useful.
>
> The idea that the correct way to initialize a string is
> (define x (string-copy "string")) is awkward. "string" is a read-only
> but copying it makes it modifyiable? Copying implies mutability?
>
> Copying doesn't imply modifying mutability in any other data type.
Huh?
(set-car! '(4 5) 3) => bad
(set-car! (list-copy '(4 5)) 3) => ok
Similar with literal vectors.
Why should strings be different here?
--
David Kastrup
next prev parent reply other threads:[~2012-01-04 9:41 UTC|newest]
Thread overview: 117+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-03 4:08 What's wrong with this? Bruce Korb
2012-01-03 15:03 ` Mike Gran
2012-01-03 16:26 ` Guile: " Bruce Korb
2012-01-03 16:30 ` Mike Gran
2012-01-03 22:24 ` Ludovic Courtès
2012-01-03 23:15 ` Bruce Korb
2012-01-03 23:33 ` Ludovic Courtès
2012-01-04 0:55 ` Bruce Korb
2012-01-04 3:12 ` Noah Lavine
2012-01-04 17:37 ` bytevector -- was: " Bruce Korb
2012-01-04 21:17 ` Ludovic Courtès
2012-01-04 22:36 ` Bruce Korb
2012-01-05 0:01 ` Ludovic Courtès
2012-01-05 18:36 ` non-reproduction of initial issue -- was: " Bruce Korb
2012-01-05 18:50 ` Mark H Weaver
2012-01-04 12:19 ` Ian Price
2012-01-04 17:16 ` Bruce Korb
2012-01-04 17:21 ` Andy Wingo
2012-01-04 17:39 ` David Kastrup
2012-01-04 21:52 ` Ian Price
2012-01-04 22:18 ` Bruce Korb
2012-01-04 23:22 ` Mike Gran
2012-01-04 23:59 ` Mark H Weaver
2012-01-05 17:22 ` Bruce Korb
2012-01-05 18:13 ` Mark H Weaver
2012-01-05 19:02 ` Mark H Weaver
2012-01-05 20:24 ` David Kastrup
2012-01-05 22:42 ` Mark H Weaver
2012-01-06 1:02 ` Mike Gran
2012-01-06 1:41 ` Mark H Weaver
2012-01-06 2:38 ` Noah Lavine
2012-01-06 13:37 ` Mike Gran
2012-01-06 14:11 ` David Kastrup
2012-01-06 18:13 ` Mark H Weaver
2012-01-06 19:06 ` Bruce Korb
2012-01-06 19:19 ` David Kastrup
2012-01-06 20:03 ` Mark H Weaver
2012-01-07 16:13 ` Mark H Weaver
2012-01-07 17:35 ` mutable interfaces - was: " Bruce Korb
2012-01-07 17:47 ` David Kastrup
2012-01-07 18:30 ` Mark H Weaver
2012-01-07 18:55 ` Mark H Weaver
2012-01-06 22:23 ` Guile BUG: " Bruce Korb
2012-01-06 23:11 ` Mark H Weaver
2012-01-06 23:35 ` Andy Wingo
2012-01-06 23:41 ` Bruce Korb
2012-01-07 15:00 ` Mark H Weaver
2012-01-07 15:27 ` Bruce Korb
2012-01-07 16:38 ` Mark H Weaver
2012-01-07 17:39 ` Bruce Korb
2012-01-09 15:41 ` Mark H Weaver
2012-01-09 17:27 ` Bruce Korb
2012-01-09 18:32 ` Andy Wingo
2012-01-09 19:48 ` Bruce Korb
2012-01-07 15:47 ` David Kastrup
2012-01-07 17:07 ` Mark H Weaver
2012-01-07 14:35 ` Mark H Weaver
2012-01-07 15:20 ` Mike Gran
2012-01-07 22:25 ` Ludovic Courtès
2012-01-10 9:13 ` The empty string and other empty strings Ludovic Courtès
2012-01-10 11:28 ` Mike Gran
2012-01-10 13:03 ` Mark H Weaver
2012-01-10 13:09 ` Mike Gran
2012-01-10 15:41 ` Mark H Weaver
2012-01-10 15:48 ` David Kastrup
2012-01-10 16:15 ` Mark H Weaver
2012-01-12 22:33 ` Ludovic Courtès
2012-01-13 9:27 ` David Kastrup
2012-01-13 16:39 ` Mark H Weaver
2012-01-13 17:36 ` David Kastrup
2012-01-16 8:26 ` Marijn
2012-01-16 8:47 ` David Kastrup
2012-01-20 21:31 ` Andy Wingo
2012-01-10 14:10 ` David Kastrup
2012-01-10 12:21 ` Mike Gran
2012-01-10 12:27 ` Mark H Weaver
2012-01-10 16:34 ` Ludovic Courtès
2012-01-10 17:04 ` David Kastrup
2012-01-06 23:28 ` Guile BUG: What's wrong with this? Bruce Korb
2012-01-07 20:57 ` Guile: " Ian Price
2012-01-08 5:05 ` Mark H Weaver
2012-01-06 9:23 ` David Kastrup
2012-01-05 7:22 ` David Kastrup
2012-01-04 22:46 ` Ludovic Courtès
2012-01-04 3:04 ` Mike Gran
2012-01-04 9:35 ` nalaginrut
2012-01-04 9:41 ` David Kastrup [this message]
2012-01-04 21:07 ` Ludovic Courtès
2012-01-04 10:03 ` Mark H Weaver
2012-01-04 14:29 ` Mike Gran
2012-01-04 14:45 ` David Kastrup
2012-01-04 16:47 ` Andy Wingo
2012-01-04 17:14 ` David Kastrup
2012-01-04 17:32 ` Andy Wingo
2012-01-04 17:49 ` David Kastrup
2012-01-04 18:09 ` Andy Wingo
2012-01-04 17:30 ` Bruce Korb
2012-01-04 17:44 ` David Kastrup
2012-01-04 18:26 ` Ian Price
2012-01-04 18:48 ` Mark H Weaver
2012-01-04 19:29 ` Bruce Korb
2012-01-04 20:20 ` David Kastrup
2012-01-04 23:19 ` Mark H Weaver
2012-01-04 23:28 ` Bruce Korb
2012-01-07 15:43 ` Fixed string corruption bugs (was Guile: What's wrong with this?) Mark H Weaver
2012-01-07 16:19 ` Fixed string corruption bugs Andy Wingo
2012-01-04 18:31 ` Guile: What's wrong with this? Mark H Weaver
2012-01-04 18:43 ` Andy Wingo
2012-01-04 19:29 ` Mark H Weaver
2012-01-04 19:43 ` Andy Wingo
2012-01-04 20:08 ` Bruce Korb
2012-01-04 20:14 ` David Kastrup
2012-01-04 20:56 ` Andy Wingo
2012-01-04 21:30 ` Bruce Korb
2012-01-04 17:19 ` Mark H Weaver
2012-01-05 4:24 ` Mark H Weaver
2012-01-04 22:37 ` Ludovic Courtès
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