Re: [Chicken-users] using mmap files as strings?

[F. Wittenberger]

Am Mittwoch, den 27.10.2010, 09:23 -0600 schrieb Alan Post:
> In a lisp system I worked on a few years ago, I have both a string
> type and a "static" type.  They both acted like strings, but the
> static type had a pointer+len to non-memory-pool memory, rather than
> allocating the string data with the object.  I believe also the
> static object was read-only, for my own simplicity.

This is in fact (for the sake of simplicity) what I have in mind I'd
love to have.  I can live with immutable strings as input source.  It
might require some thinking, but I bet my a* on it that this additional
care would pay off in many situations.

> I had also wanted to implement substrings, but the problem I ran
> into was that I may have a pointer *only* to a substring when the GC
> was called, and I had no way to access the full string and make sure
> it was properly copied.  I wasn't using your suggestiong above of
> having a pointer, start, and end, though I'm not sure why.

I wouldn't be either.  My contemplations took a some time already.  With
the chicken source code in front of my eyes.  That's a bad sign to
me.  :-/

However 

Am Mittwoch, den 27.10.2010, 09:17 -0700 schrieb Kon Lovett:
On Oct 27, 2010, at 5:02 AM, Jörg F. Wittenberger wrote:
> 
> <snip>
> >
> > However this would somehow have to overwrite the basic string  
> > handling.
> > I have not yet tried that, but at least the utf8 egg hints that it  
> > must
> > be possible to do so.
> 
> Not completely. Chicken library code uses sys namespace routines &  
> cached bindings for many string operations. Hooking the Chicken
string  
> representation in a routine by routine fashion will probably be
brittle.
> 

I recently noticed that several of the ##sys# prefixes have been
eliminated recently (elsewhere in the code).

Also I must ask here: do those namespaces have any special effect
besides a new symbol table entry?  If not (and that's what my
observations indicate) it should be possible to just overwrite the
bindings.  At worst it might be a case of making sure the overwrite
happens early enough, at least before the caching.

...or early enough with some help by our friendly chicken.

I mean: some Scheme compiler(s) allow call/cc only with a command line
switch.  Why should chicken not get yet another one, enabling shared
substrings (which would mean to use half way replaced string handling).
I would contribute on that one.

> pointer to the string and an index.  I rarely need to know the full
> length of the string,

But the length of the substring, don't you?