Re: What's wrong with this?

[Mike Gran <spk121@yahoo.com>]

> From: Bruce Korb <bruce.korb@gmail.com>


> My "(get ...)" function always returns a string.
> This result was assigned to "tmp-text" and the
> "(string-upcase ...)" is complaining that the input is
> read only.  Well, it isn't, so the real complaint
> is being hidden by the "string is read-only" message.
> 
> It worked until I "upgraded" to openSuSE 12.1.
> 
>>  $ guile --version
>>  guile (GNU Guile) 2.0.2
>>  .....
> 
> What is really wrong, please?
> 
>> 
>>  (set! tmp-text (get "act-text"))
>>         (set! TMP-text (string-upcase tmp-text))
>>         (string-append
>>           (if (exist? "no") "no-" "yes-")
>>           (get "act-type"))
>

There does seem to be some strangeness w.r.t. read-only
strings going on.

On Guile 1.8.8 if you create a string this way, it is
not read-only.

guile> (define y "hello")
guile> (string-set! y 0 #\x)
guile> y
"xello"

On Guile 2.0.3, if you create a string the same way, it
is read-only for some reason.

scheme@(guile-user)> (define y "hello")
scheme@(guile-user)> (string-set! y 0 #\x)
ERROR: In procedure string-set!:
ERROR: string is read-only: "hello"

%string-dump can be used to confirm this

scheme@(guile-user)> (%string-dump y)
$4 = ((string . "hello") (start . 0) (length . 5)
  (shared . #f) (read-only . #t) (stringbuf-chars . "hello")
  (stringbuf-length . 5) (stringbuf-shared . #f) (stringbuf-wide . #f))

But if you create a string with 'string' it isn't read only

scheme@(guile-user)> (define y (string #\h #\e #\l #\l #\o))
scheme@(guile-user)> (string-set! y 0 #\x)
scheme@(guile-user)> y
$7 = "xello"

-Mike