substring

substring

[.]

Hi,

Why do we need substring [1]? We already have string-copy which looks
similar to me.
(These functions take different number of arguments, but string-copy
can handle this because it's more generic.)

Is this connected with compatability, convenience or something else?

[1] http://www.gnu.org/software/guile/manual/html_node/String-Selection.html#String-Selection

Thanks

Re: substring

[Mike Gran]

>  
>Hi,
>
>Why do we need substring [1]? We already have string-copy which looks
>similar to me.
>(These functions take different number of arguments, but string-copy
>can handle this because it's more generic.)

I haven't looked at the code lately, but, it used to be that substring
would allow you to create a string that initially shared the same string
buffer as the string from which it was derived, saving memory.  Later, if
you tried to modify the substring or the parent string, it would
allocate a new string buffer for itself.  But if you never modified the parent
or the substring, they would always point to (presumably different) 
locations in the same string buffer. 
 
-Mike

Re: substring

[Ian Price]

"." <nkwerk@gmail.com> writes:

> Hi,
>
> Why do we need substring [1]? We already have string-copy which looks
> similar to me.
> (These functions take different number of arguments, but string-copy
> can handle this because it's more generic.)
>
> Is this connected with compatability, convenience or something else?
substring is in the standard, has been for ages.

-- 
Ian Price -- shift-reset.com

"Programming is like pinball. The reward for doing it well is
the opportunity to do it again" - from "The Wizardy Compiled"

Re: substring

[nalaginrut]

On Fri, 2012-09-07 at 21:49 +0400, . wrote: 
> Hi,
> 
> Why do we need substring [1]? We already have string-copy which looks
> similar to me.
> (These functions take different number of arguments, but string-copy
> can handle this because it's more generic.)
> 
> Is this connected with compatability, convenience or something else?
> 
> [1] http://www.gnu.org/software/guile/manual/html_node/String-Selection.html#String-Selection
> 

*string-copy is actually substring/copy, which is a newly allocated
string buffer.

*substring is a copy-on-write version.

*substring/shared is actually the same string buffer with the original
string. It won't do any copy operation.



> Thanks
> 

Re: substring

[Ludovic Courtès]

Hi,

nalaginrut <nalaginrut@gmail.com> skribis:

> *string-copy is actually substring/copy, which is a newly allocated
> string buffer.
>
> *substring is a copy-on-write version.

And these two procedures live at a different abstraction level: the name
‘string-copy’ suggests memory management, whereas ‘substring’ suggests
an operation on a string (which happens to use COW, but that’s an
implementation detail.)

Thanks,
Ludo’.