On 03-08-2022 11:51, Damien Mattei wrote:
> ok
> and i suppose it is the standard, i have been confused by other 
> schemes or racket where my code worked:

It happens to work in Guile too, when you use the interpreter instead of 
the compiler:

> scheme@(guile-user)> (eval `(let ((a ,(string-copy "foo"))) 
> (string-set! a 0 #\b) a) (current-module))
> $1 = "boo"
However, as implied by 
<https://lists.gnu.org/archive/html/guile-devel/2012-01/msg00135.html>, 
it's not something to rely upon.  (Maybe 'eval' should make all strings 
it encounters in the S-exp read-only first with substring/read-only, 
assuming that doesn't come with a performance cost.)

Greetings,
Maxime.