Re: string is read-only

[Jean Abou Samra]

> Le 3 août 2022 à 12:30, Taylan Kammer <taylan.kammer@gmail.com> a écrit :
> 
> On 03.08.2022 11:50, Jean Abou Samra wrote:
>> 
>> 
>>>> Le 3 août 2022 à 11:49, Taylan Kammer <taylan.kammer@gmail.com> a écrit :
>>> 
>>> On 03.08.2022 11:12, Damien Mattei wrote:
>>>> GNU Guile 3.0.1
>>>> Copyright (C) 1995-2020 Free Software Foundation, Inc.
>>>> 
>>>> Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
>>>> This program is free software, and you are welcome to redistribute it
>>>> under certain conditions; type `,show c' for details.
>>>> 
>>>> Enter `,help' for help.
>>>> scheme@(guile-user)> (define str2 "hello")
>>>> scheme@(guile-user)> (string-set! str2 4 #\a)
>>>> ice-9/boot-9.scm:1669:16: In procedure raise-exception:
>>>> string is read-only: "hello"
>>>> 
>>>> Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
>>>> scheme@(guile-user) [1]> ,q
>>>> scheme@(guile-user)> (string? str2)
>>>> #t
>>>> 
>>>> is it a bug in Guile ? :-O
>>>> 
>>>> i can only find reference to deprecated read-only string in old doc:
>>>> https://www.gnu.org/software/guile/docs/docs-1.6/guile-ref/Read-Only-Strings.html#Read%20Only%20Strings
>>>>  
>>>> <https://www.gnu.org/software/guile/docs/docs-1.6/guile-ref/Read-Only-Strings.html#Read%20Only%20Strings>
>>>> 
>>>> Regards,
>>>> 
>>>> Damien
>>> 
>>> String literals are constants, and it's intentional.
>>> 
>>> I'm not sure if it's mentioned anywhere in the manual.
>>> 
>>> If you want to get a mutable string from a literal, you can use:
>>> 
>>>  (define str (string-copy "foobar"))
>>> 
>>> -- 
>>> Taylan
>> 
>> This is standard. See the intro of
>> 
>> https://srfi.schemers.org/srfi-135/ <https://srfi.schemers.org/srfi-135/>
>> 
>>> 
> 
> This SRFI defines a new data type, which is not really relevant here.
> 
> As far as I know, Guile doesn't support it yet anyway.



I just wanted to point to the intro, which summarizes the state of literal 
string immutability in all recent RnRSes:

"""
In Scheme, strings are a mutable data type. Although it "is an error" (R5RS and 
R7RS) to use string-set! on literal strings or on strings returned by 
symbol->string, and any attempt to do so "should raise an exception" (R6RS),
"""



> -- 
> Taylan